orangutan€¦ · if the aza bornean orangutan population continues its current breeding rate (2.7...

Population Biologist Brent Johnson, [email protected] AZA Animal Program Leader Lori Perkins, [email protected] Regional Studbook Keeper & AZA Vice-Animal Program Leader Megan Elder, [email protected] AZA Ape TAG Chair Tara Stoinski, [email protected] AZA Ape TAG Vice-Chair Tracy Fenn, [email protected]

Orangutan (Pongo pygmaeus +

Pongo abelii) AZA Animal Programs

Population Viability Analysis Report

August 19, 2014

2014 Population Viability Analyses for AZA Orangutan Animal Program 1

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...................................................................................................................................2

POPULATION VIABILITY ANALYSIS (PVA) APPROACH ....................................................................................3

REPORT OVERVIEW ........................................................................................................................................4

HYBRID POPULATION VIABILITY UNDER CURRENT MANAGEMENT ..............................................................5

BORNEAN POPULATION HISTORY AND CURRENT STATUS ............................................................................6

BORNEAN MODEL SCENARIOS .......................................................................................................................9

BORNEAN POPULATION VIABILITY UNDER CURRENT MANAGEMENT ........................................................10

BORNEAN ALTERNATE MODEL SCENARIOS .................................................................................................11

SUMATRAN POPULATION HISTORY AND CURRENT STATUS .......................................................................13

SUMATRAN MODEL SCENARIOS ..................................................................................................................16

SUMATRAN POPULATION VIABILITY UNDER CURRENT MANAGEMENT .....................................................17

SUMATRAN ALTERNATE MODEL SCENARIOS ..............................................................................................18

MANAGEMENT ACTIONS .............................................................................................................................19

CONCLUSIONS ..............................................................................................................................................19

ACKNOWLEDGEMENTS ................................................................................................................................20

LITERATURE CITED ........................................................................................................................................21

DEFINITIONS .................................................................................................................................................22

APPENDICES .................................................................................................................................................23


EXECUTIVE SUMMARY Population Viability Analyses (PVA) are being conducted by Lincoln Park Zoo and Population Management Center researchers through

funding from the Institute of Museum and Library Services (IMLS). The project team uses ZooRisk 3.80 (Earnhardt et al. 2008), a PVA

modeling software, to examine what would happen to AZA populations if current conditions remain the same (the baseline scenario), and

then assess the impact of changes in reproductive rates, space availability, imports/exports, and other potential management actions

(alternate scenarios). Model scenarios for this population were developed with members of the Association of Zoos and Aquarium (AZA)

Ape Taxon Advisory Group (TAG) during summer of 2014.

POPULATION HISTORY/CURRENT STATUS Bornean orangutans (Pongo pygmaeus) have been consistently held in AZA institutions since 1940. Through a combination of importations

of animals from outside of AZA and zoo births, the population grew to a size near 75 individuals by 1969. The population currently includes

84 individuals. In the past 10 years, the population has had an average of 2.7 births/year. Current gene diversity is high (97.2%) and

inbreeding is low (average inbreeding coefficient of 0.0004).

Sumatran orangutans (Pongo abelii) have been consistently housed in North American institutions since 1928, although the population size

remained low (<30 individuals) until 1960. After that year, the population grew through a combination of importations of animals from

outside of the formally managed population and zoo births to a peak size of 105 individuals in 1997. The population averaged 2.8

births/year in the past 10 years and currently includes 85 individuals. At present, the Sumatran orangutan population has high gene

diversity (97.6%) and low inbreeding (average inbreeding coefficient of 0.0056).

For each orangutan population, managers have been moving toward a standard of parent rearing and more prolonged time that offspring

spend with their mother. They intend to maintain a minimum of 8-year interbirth intervals among females (except when infant mortalities

occur) to allow them to fully raise their young.

PVA RESULTS Model results indicate that hybrid orangutans will age out of AZA institutions in approximately 32 years, which could increase spaces for

the other orangutan populations. If the AZA Bornean orangutan population continues its current breeding rate (2.7 births/year in the past

10 years), it is expected to have a 4% chance of extinction or approximately 16 individuals remaining in 100 years. However, increasing

breeding is predicted to allow the AZA Bornean orangutan population to remain stable over the next 100 years. For the population to

maintain its current size, it would need to produce an average of ~4 births per year over the next 10 years. If the population produces ~5

births/year, it could fill 115 potential spaces (including half of those currently occupied by hybrids) in approximately 32 years.

Under its current breeding rate (2.8 births/year in the past 10 years), the formally managed Sumatran orangutan population is predicted to

decline to an average of 50 individuals over the next 100 years. Increasing breeding is predicted to also allow the Sumatran orangutan

population to remain stable over the next 100 years. To maintain its current size, the population should produce an average of ~4 births

per year over the next 10 years. By producing ~4 births/year over the next decade and ~5 births every following year, the population could

fill 115 potential spaces in approximately 33 years. Increasing breeding rates (to either maintain the current population size or fill potential

spaces) is also expected to maintain the genetic health of each orangutan population over the next century.

MANAGEMENT ACTIONS The AZA Orangutan Animal Programs should consider the following changes to current management strategies:

Re-allocate spaces currently occupied by hybrids as they become available: Because spaces are expected to become available as hybrid

orangutans age out of AZA institutions, managers should ensure that these spaces are allocated to Bornean and Sumatran orangutans to

maintain each of these populations at a larger, stable size with the best possible genetic health.

Increase breeding rates: For each orangutan population, breeding should be increased from ~3 births per year to a minimum of ~4 births

each year to maintain the current population size. To fill spaces currently occupied by hybrid orangutans as they become available, the

Bornean population should produce ~5 births per year. The Sumatran population, however, should produce ~4 births each year for the

next decade and ~5 births every following year in order to do so. To achieve these higher breeding rates, it may not be possible to

immediately implement the recommended 8-year interbirth intervals. If higher breeding rates could be maintained, each population may

become demographically stable and maintain its genetic health.


FULL REPORT

POPULATION VIABILITY ANALYSIS (PVA) APPROACH

A Population Viability Analysis (PVA) is a model that projects the likely future status of a population. PVAs are used to

evaluate long-term demographic and genetic sustainability and extinction risk, identify key factors impacting a population’s

dynamics, and compare alternative management strategies.

This PVA utilizes ZooRisk, a computer software package that models the future dynamics of a cooperatively-bred population

using that population’s age and sex structure, mortality and reproductive rates, and genetic structure (Earnhardt et al., 2008).

ZooRisk is individual-based, meaning it tracks every animal (current and future) in the population over time. It also includes

stochasticity, the randomness in mortality, fecundity, and birth sex ratios among individuals, which is especially important for

small populations. Because of this stochasticity, we run each model many times, allowing us to determine the range of

potential outcomes a population could experience under a given set of conditions.

The most powerful use of PVAs is to compare a baseline scenario, reflecting the population’s likely future trajectory if no

management changes are made, to alternate scenarios reflecting potential management changes. For zoo and aquarium

populations, these alternate scenarios typically involve varying breeding rates (probability of breeding, or p(B)), potential

space for the population, importation or exportation rates, mortality rates, or genetic management strategies. These

comparisons can help evaluate the relative costs and benefits of possible management actions. Because the future can be

uncertain and difficult to predict, model results are most appropriately used to compare between scenarios (e.g. relative to

each other) rather than as absolute predictions of what will happen.

Full documentation on ZooRisk can be found in the software’s manual (Faust et al., 2008); complete details on the modeling

approach for this PVA, including data sources, parameter values, and model setup, can be found in Appendix A.


REPORT OVERVIEW

Orangutans in the entire, formally managed population (i.e., at AZA institutions and Toronto Zoo) have historically included

individuals of both the Bornean (Pongo pygmaeus) and Sumatran species (Pongo abelii), as well as hybrids of the two and

individuals of unknown origin (Fig. 1). Today, relatively even numbers of Bornean and Sumatran orangutans are held among

these institutions (84 Bornean orangutans and 85 Sumatran orangutans), with 45 remaining individuals being hybrids. In this

report we very briefly present a scenario pertaining to the hybrid population, and then separately describe the population

history, status, and model results for the Bornean and Sumatran orangutan populations.

0

50

100

150

200

250

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Sumatran

Bornean

Hybrid

Unknown

Year

Nu

mb

er

of

Ind

ivid

ual

s

Figure 1. Number of orangutans in the entire, formally managed population since 1940.


HYBRID POPULATION VIABILITY UNDER CURRENT MANAGEMENT

Currently, 45 hybrid orangutans (21 males, 24 females) are housed at 23 AZA institutions. The majority of these individuals

are currently above 25 years old (Fig. 2). Because hybrids exist in zoos only as a result of breeding that occurred prior to the

recognition of two distinct orangutan species, the Ape TAG plans to manage the hybrid population without any further

reproduction. In this management scenario, the hybrid population can be expected to age out of zoos in approximately 32

years (Fig. 3, Table 1).

Table 1. Baseline model results.

SCENARIO

DEMOGRAPHICS

Initial Population

Size Size in Year 25

1 Size in Year 100

1

Probability of

Reaching Spaces

(%)

Probability of

Extinction (%)

Median Years until

Reaching

Extinction

A p(B) = 0% 45 2 ± 1 0 0 100 32 1

Mean value + 1 Standard Deviation, taken across 1000 iterations. If an iteration goes extinct that value is not included in the calculation, so results may only reflect a few iterations

in scenarios with a high probability of extinction.

Figure 2. The age distribution of the total hybrid population (21.24) within AZA institutions.

0

10

20

30

40

50

60

70

80

1950 1970 1990 2010 2030 2050 2070 2090 2110

Nu

mb

er

of

Ind

ivid

ual

s

Year

A) p(B) = 0% Historic

Figure 3. Historical and projected mean population size with no future

breeding. Projected results are averaged across 1000 model iterations.


Table 2. Summary of demographic statistics for the AZA population. Population Sizes Total (male.female.unknown)

Current population 84 (33.51.0)

Potentially breeding population 79 (33.46.0)

Annual rates over the last decade Mean (min-max)

Population Growth (Lambda, λ) 1.006 (0.932-1.072)

Births 2.7 (1-7)

Deaths 2.6 (0-7)

Imports 0.4 (0-4)

Exports 0

BORNEAN POPULATION HISTORY AND CURRENT STATUS

Demographics Based on the international orangutan studbook (Elder,

2014), Bornean orangutans have been consistently held in

AZA institutions since 1940. Initial growth of the population

was driven exclusively by importations of wild-caught

individuals (Figs. 4 and 5a). (Note that throughout this

section, “imports” are animals entering AZA institutions

which may be coming from non-AZA institutions such as the

private sector, EAZA, other zoo regions, or from the wild,

and conversely “exports” are animals exiting AZA institutions

and going into non-AZA populations, such as other zoo

regions or being released into the wild). Regular breeding

of Bornean orangutans in AZA zoos began in 1960, when the

population size was 39 individuals. Since 1969, the

population has remained above approximately 70

individuals (Fig. 4). The population peaked in size at 89

individuals in 2009.

Over the last 10 years (2004-2013, based on the studbook currentness date), the Bornean orangutan population has

increased slightly in size from 78 to 84 individuals and has experienced an average annual growth rate of 0.6%, although

specific annual growth rates have ranged from -6.8% to +7.2% (Table 2). The population has averaged 0.0% annual growth in

the past five years. In the past decade, the population has averaged 2.7 births per year (which corresponds to each female

having an 11.5% probability of breeding in a given year;

see Appendix A) and 0.4 imports each year.

As of April 26th

, 2014 (the studbook currentness date), the

Bornean orangutan population consisted of 84 animals (33

males, 51 females). Five females are excluded from the

breeding population, based on being beyond the

reproductive age window (14-42; see Appendix A) or being

sterile. This leaves a potentially breeding population of

79 (33.46) individuals. See Appendix B for a complete list

0123456789

10

1940 1950 1960 1970 1980 1990 2000 2010

Nu

mb

er

of

Ind

ivid

ual

s

Year

Births Imports

0123456789

10

1940 1950 1960 1970 1980 1990 2000 2010

Nu

mb

er

of

Ind

ivid

ual

s

Year

Deaths Exportsa) b)

Figure 5. Number of a) births and imports and b) deaths and exports in the population since 1940. Imported animals entering AZA institutions may be coming from non-AZA institutions (private sector, EAZA, other zoo regions, or from the wild); exported animals may be going to other institutions outside of AZA in North America, other regions, or being released into the wild.

0

10

20

30

40

50

60

70

80

90

100

1940 1950 1960 1970 1980 1990 2000 2010

Nu

mb

er

of

Ind

ivid

ual

s

Year

Total Males Females

Figure 4. Number of Bornean orangutans in AZA institutions since 1940.


of the individuals included in the model and their reproductive status.

The population has an age structure that is largely columnar with many empty age classes (Fig. 6a). There are also few

individuals in lower age classes due to somewhat low reproduction in the past seven years. The potentially breeding

population currently displays a female-biased sex ratio of 1.4 females per male (Fig. 6b). Orangutans generally breed best

when held in groups with 1 to 3 females per male, therefore the current sex ratio is appropriate for the management of this

population.

Figure 6. The population’s age distribution within AZA institutions, divided into a) the total population 84 (33.51.0) and b) the potentially breeding population 79 (33.46.0).

Genetics The Bornean orangutan population’s pedigree is 100%

known (Table 3), and no analytical assumptions were

necessary. The managed population is descended from 50

founders with no additional potential founders remaining in

the population. Current gene diversity is estimated to be

97.23%. As gene diversity falls, reproduction may become

increasingly compromised by lower birth weights, greater

neonatal mortality, and other negative factors.

The population has a low mean inbreeding level of 0.0004 (a mean inbreeding coefficient of 0.0625 is equivalent to mating

between first cousins with no prior inbreeding). One of the largest genetic threats to small populations is the potential for

inbreeding depression, in which breeding between close relatives results in reductions in fecundity or litter size, increases in

infant mortality, and other detrimental effects (DeRose and Roff, 1999; Koeninger Ryan, et al., 2002; Ballou and Foose, 1996;

Reed and Frankham, 2003). Given the low level of inbreeding in the Bornean orangutan population, the small number of

individuals with inbreeding values above 0 prevented us from statistically testing for possible effects on infant mortality. It is

unlikely that inbreeding is impacting the population at this time; however, inbreeding may become a threat in the future and

should therefore be avoided. Because modeling inbreeding depression adds an additional layer of complexity to

interpretation of results, we have not included a “standard” inbreeding depression effect in the PVA models. There are

several strategies that can delay the effects or lower the probability of inbreeding depression including pairing based on

mean kinship and importing and breeding unrelated individuals (Ballou and Lacy, 1995). These strategies were modeled for

Table 3. Summary of starting genetic statistics for the population.

Percentage of pedigree known 100%

Genetic Diversity (GD) 97.23%

Population mean kinship (MK) 0.0277

Mean inbreeding (F) 0.0004

Mean generation time (T) (years) 20.9

Number of generations in 100 model years 4.8

a) b)


all scenarios except those without genetic management. Because inbreeding depression is not included, readers should

consider that model results may be optimistic if inbreeding depression begins to impact the population.

Management ZooRisk can include a space limitation on population growth, reducing breeding as the population approaches the potential

space limit. This mimics the way a population manager would recommend fewer pairs when at capacity. To accurately model

the “potential space” for a population, we use either a) the projected spaces in 5 years based on a TAG’s Regional Collection

Plan (RCP) or, if that value is unavailable or inappropriate, b) the current population size + 10% or 10 individuals, whichever is

greater. These values are also placed in context of current institutional interest by the Species Coordinator. The Ape TAG’s

most recent space survey set the target size for Bornean orangutans over 4 years old at 85 individuals (AZA Ape Taxon

Advisory Group, 2007), however some additional spaces could become available if the population grows. Given this fact, and

because animals under 4 four years old still occupy space in ZooRisk, we allowed for 100 potential spaces in our model.

The AZA Bornean orangutan population is currently designated as a Green Program. The population is housed at 25

institutions, with 21 having at least one potential breeding pair.

Since the late 1980s, parent rearing has become the primary means of raising young Bornean orangutans in zoos (Fig. 7).

Additionally, there has been an increasing trend in the interbirth intervals among females raising offspring. Managers intend

to have interbirth intervals no shorter than 8 years except when infant mortalities occur to ensure proper social development

of the offspring. If reproductively viable females in the population were to maintain an average interbirth interval of 8 years,

the female probability of breeding (p[B]) in any given year would be equal to 12.5% (see appendix A for more information on

p[B]).

Figure 7. Interbirth intervals related to each rearing style over time.

0

2

4

6

8

10

12

14

16

1950 1960 1970 1980 1990 2000 2010

Inte

rbir

th In

terv

al (

Ye

ars)

Year

Parent Hand Foster

Supplemental Unknown Trend (Parent)


BORNEAN MODEL SCENARIOS

Model scenarios were created to reflect what would happen if current management approaches continued (baseline) and to

address potential alternate management strategies (Table 4). Model setup is described more fully in Appendix A. Scenarios

are described in more detail in the following sections.

Table 4. ZooRisk Model Scenarios

Scenario Name Scenario Description p(B) Spaces

Baseline Scenario:

B. Baseline; p(B) = 11.5% Reproduction to match past 10 years (2.7 births/year) 11.5% 100

Alternate Scenarios:

C. p(B) = 19% Reproduction required to sustain current population size 19% 100

D. p(B) = 25%; spaces = 115 Reproduction required to fill hybrid spaces as they become

available (i.e., approaching 115 spaces over the next 32 years) 25% 115

p(B) = Probability of Breeding


BORNEAN POPULATION VIABILITY UNDER CURRENT MANAGEMENT BASELINE MODEL PVA RESULTS

We examined the viability of the AZA Bornean orangutan

population under current management: 11.5% female

probability of breeding (equivalent to 2.7 births/year over the

past 10 years) and no imports or exports. The population

currently has a target size of 85 for individuals older than 4

years old, however some additional spaces could become

available if the population grows. Because of this flexibility in

the availability of spaces, and the fact that animals younger

than 4 years old hold space within our models, we allowed for

100 potential spaces in the baseline scenario. See Appendix A

for full details on all model parameters.

If the current breeding rate continues, the Bornean orangutan

population has a 4% chance of reaching extinction (Table 5). If

it does not go extinct, the population is expected to have

approximately 16 individuals remaining in 100 years (Table 5,

Fig. 8). In this scenario, the population would retain 84.4% gene diversity and fairly low inbreeding (average inbreeding

coefficient (F) = 0.055) after 100 years, although inbreeding would begin approaching the equivalent of mating between first

cousins (F = 0.063). The population is predicted to have a Vulnerable risk status in zoos and aquariums due to its declining

gene diversity (see Appendix C).


SCENARIO

DEMOGRAPHICS GENETICS

OVERALL

POPULATION

STATUS2

Initial

Population

Size

Size in

Year 251

Size in

Year

1001

Probability

of Reaching

Spaces (%)

Probability

of

Extinction

(%)

Initial

GD (%)

GD

Retained

in Year

1001

Initial F

F Retained

in Year

1001

B p(B) = 11.5% 84 60 ± 9 16 ± 10 1 4 97.2 84.4 ± 8.8 0.0004 0.055 ±

0.034 Vulnerable

GD = gene diversity, F = inbreeding coefficient 1 Mean value + 1 Standard Deviation, taken across 1000 iterations. If an iteration goes extinct that value is not included in the calculation, so results may only reflect a few iterations

in scenarios with a high probability of extinction. 2ZooRisk uses five standardized tests to give a summary risk score for each scenario, from Low Risk (most secure), Vulnerable, Endangered, to Critical (least secure). For more details

on this score, see Appendix C.

0

20

40

60

80

100

1980 2000 2020 2040 2060 2080 2100

Nu

mb

er

of

Ind

ivid

ual

s

Year

B. Bornean baseline; p(B) = 11.5%

Historic

Potential Space

Figure 8. Historical and projected mean population size under the baseline model scenario. Projected results are averaged across 1000 model iterations.


BORNEAN ALTERNATE MODEL SCENARIOS

We explored the impacts of altering the probability of breeding for the Bornean orangutan population in order to maintain

the population at its current size or increase the population to fill all potential spaces. For the population to sustain its

current size of 84 individuals for the next 100 years (Fig. 9, Table 6), it needs to produce an average of ~4 births/year (p(B) =

19%, scenario C; Fig. 10). Under this breeding rate, the population is expected to maintain high gene diversity (94.3%) and

fairly low inbreeding (mean inbreeding coefficient (F) = 0.043) over the next 100 years, although inbreeding would begin

approaching the equivalent of mating between first cousins (F = 0.063). Note that a p(B) = 19% is approximately equivalent

to reproductively viable females in the population maintaining an average interbirth intervals of 5.3 years. This interval could

account for infant mortality, meaning that females who lost infants would likely have shorter interbirth intervals while those

that had surviving infants could have longer ones.

We estimate that 115 potential spaces could be available for the Bornean orangutan population after hybrids age out of AZA

zoos in approximately 32 years (scenario A; Table 1), which is equal to the population’s target size of 85 individuals plus ~8

spaces for offspring and half of spaces previously occupied by hybrids (~22 spaces). If the population produces an average of

~5 births/year, it could fill the 115 potential spaces in approximately 32 years (p(B) = 25%, scenario D; Figs. 9 and 10). A p(B)

= 25% is equivalent to every reproductively viable female in the population maintaining an average interbirth interval of 4

years (which would be an average of intervals with the first offspring living and the first offspring not surviving). In this

management scenario, the population would maintain high gene diversity (95.1%) and fairly low inbreeding levels (F = 0.039)

over the next century (Table 6). In both increased breeding scenarios, the population is projected to retain a Low Risk status

in zoos (Appendix C).

Table 6. Model results for all Bornean orangutan scenarios.

SCENARIO


OVERALL

POPULATION

STATUS2

Initial

Population

Size

Size in

Year 251

Size in

Year

1001

Probability

of Reaching

Spaces (%)

Probability

of

Extinction

(%)

Initial

GD (%)

GD

Retained

in Year

1001

Initial F

F Retained

in Year

1001

B p(B) = 11.5% 84 60 ± 9 37 ± 13 1 0 97.2 84.4 ± 8.8 0.0004 0.055 ±

0.034 Vulnerable

C p(B) = 19% 84 90 ± 10 86 ± 16 85 0 97.2 94.3 ± 0.8 0.0004 0.043 ±

0.009 Low Risk

D p(B) = 25%;

spaces = 115 84 104 ± 7 114 ± 4 100 0 97.2 95.1 ± 0.2 0.0004

0.039 ±

0.007 Low Risk

GD = gene diversity, F = inbreeding coefficient 1 Mean value + 1 Standard Deviation, taken across 1000 iterations. If an iteration goes extinct that value is not included in the calculation, so results may only reflect a few iterations




0

20

40

60

80

100

120

1940 1970 2000 2030 2060 2090

Nu

mb

er

of

Ind

ivid

ual

s

Year

C. Bornean; p(B) = 19%D. Bornean; p(B) = 25%; space = 115Potential SpaceHistoric

Figure 9. Historical and projected mean population size under alternate

model scenarios. Projected results are averaged across 1000 model

iterations.

0

1

2

3

4

5

6

7

2000 2020 2040 2060 2080 2100

Nu

mb

er

of

Hat

che

s

Year

C. Bornean; p(B) = 19%

D. Bornean; p(B) = 25%; space = 115

Past 10 Years

Figure 10. Number of total births in the AZA population in the past decade and projected mean number of births under alternate model scenarios. Projected results are averaged across 1000 model iterations.


Table 7. Summary of demographic statistics for the population. Population Sizes Total (male.female.unknown)

Current population 85 (36.48.1)

Potentially breeding population 68 (34.33.1)

Annual rates over the last decade Mean (min-max)

Population Growth (Lambda, λ) 0.996 (0.932-1.049)

Births 2.8 (1-4)

Deaths 3.2 (0-7)

Imports 0.2 (0-1)

Exports 0.2 (0-1)

SUMATRAN POPULATION HISTORY AND CURRENT STATUS

Demographics Based on the international orangutan studbook (Elder,

2014), Sumatran orangutans have been consistently held in

AZA zoos and one non-AZA partner institution (Toronto Zoo)

since 1928. However, the population size remained low

(<30 individuals) until 1960 (Fig. 11). Regular breeding of

Sumatran orangutans within the formally managed

population began the following year (Fig. 12a). Initial

population growth was driven by importations of wild-

caught individuals, as well as zoo births, and the population

reached over 80 individuals in 1969 (Fig. 11). (Note that

throughout this section, “imports” are animals entering the

formally managed population which may be coming from

outside institutions such as the private sector, EAZA, other

zoo regions, or from the wild, and conversely “exports” are

animals exiting the formally managed population and going

into other populations, such as other zoo regions or being released into the wild). In 1997, the Sumatran orangutan

population size peaked at 105 individuals.

Over the last 10 years (2004-2013, based on the studbook currentness date), the formally managed population has decreased

slightly in size from 91 to 85 individuals and has experienced an average annual growth rate of -0.4%, although specific

annual growth rates have ranged from -6.8% to +4.9% (Table 7). The population has averaged +1.2% annual growth in the

past five years. In the past decade, the population has had

an average of 2.8 births per year (which corresponds to

each female having a 14.8% probability of breeding in a

given year; see Appendix A), as well as an average of 0.2

imports and 0.2 exports each year.

As of April 26th

, 2014 (the studbook currentness date), the

Sumatran orangutan population consisted of 85

individuals (36 males, 48 females, 1 unknown).

Seventeen animals (2 males, 15 females) are excluded

0

2

4

6

8

10

12

14

16

1920 1940 1960 1980 2000

Nu

mb

er

of

Ind

ivid

ual

s

Year

Births Imports

0

2

4

6

8

10

12

14

16

1920 1940 1960 1980 2000

Nu

mb

er

of

Ind

ivid

ual

s

Year

Deaths Exportsa) b)

Figure 12. Number of a) births and imports and b) deaths and exports in the population since 1928. Imported animals entering the formally managed population may be coming from outside institutions (private sector, EAZA, other zoo regions, or from the wild); exported animals may be going to other institutions outside of the formally managed in North America, other regions, or being released into the wild.

0

20

40

60

80

100

120

1920 1940 1960 1980 2000

Nu

mb

er

of

Ind

ivid

ual

s

Year

Total Males Females

Figure 11. Number of Sumatran orangutans in the formally managed

population since 1928.


from the breeding population, based on being beyond the reproductive age window (10-45 for males, 14-45 for females; see

Appendix A), having health or behavioral issues, or being sterile. This leaves a potentially breeding population of 68

(34.33.1) individuals. See Appendix B for a complete list of the individuals in the model and their reproductive status.

The formally managed population has an age structure that is largely columnar with many empty age classes (Fig. 13a). The

potentially breeding population currently displays an even sex ratio (Fig. 13b). Orangutans generally breed best when held in

groups with 1 to 3 females per male, therefore the current sex ratio is appropriate for the management of this population.

However, managers are concerned about the loss of females from the potentially breeding population, which could cause a

male-biased sex ratio.

Figure 13. The population’s age distribution within AZA and partner institutions, divided into a) the total population 85 (36.48.1) and b) the potentially

breeding population 68 (34.33.1).

Genetics The Sumatran orangutan population’s pedigree is 100%

known (Table 8), and no analytical assumptions were

necessary. The managed population is descended from 50

founders with no additional potential founders remaining in

the population. Current gene diversity is estimated to be

97.58%. As gene diversity falls, reproduction may become

increasingly compromised by lower birth weights, greater

neonatal mortality, and other negative factors.

The population has a low mean inbreeding level of 0.0056 (a mean inbreeding coefficient of 0.0625 is equivalent to mating

between first cousins with no prior inbreeding). One of the largest genetic threats to small populations is the potential for

inbreeding depression, in which breeding between close relatives results in reductions in fecundity or litter size, increases in

infant mortality, and other detrimental effects (DeRose and Roff, 1999; Koeninger Ryan, et al., 2002; Ballou and Foose, 1996;

Reed and Frankham, 2003). Given the low level of inbreeding in the Sumatran orangutan population, the small number of

individuals with inbreeding values above 0 prevented us from statistically testing for possible effects on infant mortality. It is

unlikely that inbreeding is impacting the population at this time; however, inbreeding may become a threat in the future and

should therefore be avoided. Because modeling inbreeding depression adds an additional layer of complexity to

Table 8. Summary of starting genetic statistics for the population.

Percentage of pedigree known 100%

Genetic Diversity (GD) 97.58%

Population mean kinship (MK) 0.0242

Mean inbreeding (F) 0.0056

Mean generation time (T) (years) 24.7

Number of generations in 100 model years 4.0

a) b)


interpretation of results, we have not included a “standard” inbreeding depression effect in the PVA models. There are

several strategies that can delay the effects or lower the probability of inbreeding depression including pairing based on

mean kinship and importing and breeding unrelated individuals (Ballou and Lacy, 1995). These strategies were modeled for

all scenarios except those without genetic management. Because inbreeding depression is not included, readers should

consider that model results may be optimistic if inbreeding depression begins to impact the population.

Management ZooRisk can include a space limitation on population growth, reducing breeding as the population approaches the potential

space limit. This mimics the way a population manager would recommend fewer pairs when at capacity. To accurately model

the “potential space” for a population, we use either a) the projected spaces in 5 years based on a TAG’s Regional Collection

Plan (RCP) or, if that value is unavailable or inappropriate, b) the current population size + 10% or 10 individuals, whichever is

greater. These values are also placed in context of current institutional interest by the Species Coordinator. The Ape TAG’s

most recent space survey set the target size for Sumatran orangutans over 4 years old at 85 individuals (AZA Ape Taxon

Advisory Group, 2007), however some additional spaces could become available if the population grows. Given this fact, and

because animals under 4 four years old still occupy space in ZooRisk, we allowed for 100 potential spaces in our model.

The AZA Sumatran orangutan population is currently designated as a Green Program. The formally managed population is

housed at 28 institutions, including one non-AZA institution (Toronto Zoo). Nineteen institutions have at least one potential

breeding pair.

Since the late 1980s, parent rearing has become the primary means of raising young Sumatran orangutans in zoos (Fig. 14).

Additionally, there has been an increasing trend in the interbirth intervals among females raising offspring. Managers intend

to have interbirth intervals no shorter than 8 years except when infant mortalities occur to ensure proper social development

of the offspring. If reproductively viable females in the population were to maintain an average interbirth interval of 8 years,

the female probability of breeding (p[B])in any given year would be equal to 12.5% (see appendix A for more information on

p[B]).

Figure 14. Interbirth intervals related to each rearing style over time.

0

5

10

15

20

25

30

1930 1940 1950 1960 1970 1980 1990 2000 2010

Inte

rbir

th In

terv

al (

Ye

ars)

Year

Parent Hand Foster

Supplemental Unknown Trend (Parent)


SUMATRAN MODEL SCENARIOS

Model scenarios were created to reflect what would happen if current management approaches continued (baseline) and to

address potential alternate management strategies (Table 9). Model setup is described more fully in Appendix A. Scenarios

are described in more detail in the following sections.

Table 9. ZooRisk Model Scenarios

Scenario Name Scenario Description p(B) Spaces

Baseline Scenario:

E. Baseline; p(B) = 14.8% Reproduction to match past 10 years (2.8 births/year) 14.8% 100

Alternate Scenarios:

F. p(B) = 18% Reproduction required to sustain current population size 18% 100

G. p(B) = 25%; spaces = 115 Reproduction required to fill hybrid spaces as they become

available (i.e., approaching 115 spaces over the next 32 years) 25% 115

p(B) = Probability of Breeding


SUMATRAN POPULATION VIABILITY UNDER CURRENT MANAGEMENT

BASELINE MODEL PVA RESULTS

We examined the viability of the formally managed

Sumatran orangutan population under current

management: 14.8% female probability of breeding

(equivalent to 2.8 births/year over the past 10 years) and no

imports or exports. The population currently has a target

size of 85 for individuals older than 4 years old, however

some additional spaces could become available if the

population grows. Because of this flexibility in the

availability of spaces, and the fact that animals younger than

4 years old hold space within our models, we allowed for

100 potential spaces in the baseline scenario. See Appendix

A for full details on all model parameters.

Under its current breeding rate, the Sumatran orangutan

population is expected to decline to approximately 50

individuals over the next 100 years (Fig. 15). However, the

population would retain high gene diversity (92.2%) and fairly low inbreeding (average inbreeding coefficient (F) = 0.049)

after 100 years, although inbreeding would begin approaching the equivalent of mating between first cousins (F = 0.063;

Table 10). The population is predicted to maintain a Low Risk status in zoos and aquariums over the next century (see

Appendix C).


SCENARIO


OVERALL

POPULATION

STATUS2

Initial

Population

Size

Size in

Year 251

Size in

Year

1001

Probability

of Reaching

Spaces (%)

Probability

of

Extinction

(%)

Initial

GD (%)

GD

Retained

in Year

1001

Initial F

F Retained

in Year

1001

E p(B) = 14.8% 85 67 ± 9 50 ± 20 6 0 97.6 92.2 ± 2.1 0.0056 0.049 ±

0.015 Low Risk

GD = gene diversity, F = inbreeding coefficient 1




0

20

40

60

80

100

1920 1950 1980 2010 2040 2070 2100

Nu

mb

er

of

Ind

ivid

ual

s

Year

E. Sumatran baseline; p(B) = 14.8%

Historic

Potential Space

Figure 15. Historical and projected mean population size under the baseline model scenario. Projected results are averaged across 1000 model iterations.


SUMATRAN ALTERNATE MODEL SCENARIOS

We explored the impacts of altering the probability of breeding for the Sumatran orangutan population in order to maintain

the population at its current size or increase the population to fill all potential spaces. For the population to sustain its

current size of 85 individuals for the next 100 years (Fig. 16, Table 11), it needs to produce an average of ~4 births/year (p(B)

= 18%, scenario F; Fig. 17). Under this breeding rate, the population is expected to maintain high gene diversity (94.2%) and

fairly low inbreeding (F = 0.047) at 100 years, although inbreeding would begin approaching the equivalent of mating

between first cousins (F = 0.063). Note that a p(B) = 18% is approximately equivalent to reproductively viable females in the

population maintaining an average interbirth interval of 5.6 years. This interval could account for infant mortality, meaning

that females who lost infants would likely have shorter interbirth intervals while those that had surviving infants could have

longer ones.

We estimate that 115 potential spaces could be available for the Sumatran orangutan population after hybrids age out of AZA

zoos in approximately 32 years (scenario A; Table 1), which is equal to the population’s target size of 85 individuals plus ~8

spaces for offspring and half of spaces previously occupied by hybrids (~22 spaces). If the population produces an average of

~4 births/year over the next decade and ~5 births/year every following year, it could fill the 115 potential spaces in

approximately 33 years (p(B) = 25%, scenario G; Figs. 16 and 17). A p(B) = 25% is equivalent to every reproductively viable

female in the population maintaining an average interbirth interval of 4 years (which would be an average of intervals with

the first offspring living and the first offspring not surviving). In this management scenario, the population would maintain

high gene diversity (95.3%) and fairly low inbreeding (F = 0.040) over the next 100 years (Table 11). In either increase

breeding scenario, the Sumatran orangutan population is projected to retain a Low Risk status in zoos (Appendix C).

Table 11. Model results for all Sumatran orangutan scenarios.

SCENARIO


OVERALL

POPULATION

STATUS2

Initial

Population

Size

Size in

Year 251

Size in

Year

1001

Probability

of Reaching

Spaces (%)

Probability

of

Extinction

(%)

Initial

GD (%)

GD

Retained

in Year

1001

Initial F

F Retained

in Year

1001

E p(B) = 14.8% 85 67 ± 9 50 ± 20 6 0 97.6 92.2 ± 2.1 0.0056 0.049 ±

0.015 Low Risk

F p(B) = 18% 85 80 ± 11 89 ± 14 74 0 97.6 94.2 ± 0.8 0.0056 0.047 ±

0.011 Low Risk

G p(B) = 25%;

spaces = 115 85 100 ± 9 114 ± 3 100 0 97.6 95.3 ± 0.2 0.0056

0.040 ±

0.008 Low Risk

GD = gene diversity, F = inbreeding coefficient 1





MANAGEMENT ACTIONS The AZA Orangutan Animal Programs should consider the following changes to current management strategies:

Re-allocate spaces currently occupied by hybrids as they become available: Because spaces are expected to

become available as hybrid orangutans age out of AZA institutions, managers should ensure that these spaces are

allocated to Bornean and Sumatran orangutans to maintain each of these populations at a larger, stable size with

the best possible genetic health.

Increase breeding rates: For each orangutan population, breeding should be increased from ~3 births per year to a

minimum of ~4 births each year to maintain the current population size. To fill spaces currently occupied by hybrid

orangutans as they become available, the Bornean population should produce ~5 births per year. The Sumatran

population, however, should produce ~4 births each year for the next decade and ~5 births every following year in

order to do so. To achieve these higher breeding rates, it may not be possible to immediately implement the

recommended 8-year interbirth intervals. If higher breeding rates could be maintained, each population may

become demographically stable and maintain its genetic health.

CONCLUSIONS This model is a scientifically-sound comprehensive tool to be used by population managers for assessing future directions for

the animal program. This PVA report is provided to the AZA community and others to integrate into management of the

important species within our care. The PVA model results are intended to provide the necessary data to make science-based

decisions.

Our model results illustrate that, under current management practices, each orangutan population can be expected to

decline. Increasing breeding rates by approximately one or two births each year could ensure that each population maintains

a stable size over the next 100 years. Additionally, allocating spaces currently occupied by hybrids to Bornean and Sumatran

orangutans will help to better maintain the demographic and genetic stability of each of these populations. The AZA

Orangutan Animal Programs should follow these recommended management strategies in order to keep both orangutan

populations on the path towards long-term sustainability within AZA institutions.

0

20

40

60

80

100

120

1920 1950 1980 2010 2040 2070 2100

Nu

mb

er

of

Ind

ivid

ual

s

Year

F. Sumatran; p(B) = 18%

G. Sumatran; p(B) = 25%; space = 115

Figure 16. Historical and projected mean population size under alternate

model scenarios. Projected results are averaged across 1000 model

iterations.

0

1

2

3

4

5

6

2000 2020 2040 2060 2080 2100

Nu

mb

er

of

Hat

che

s

Year

F. Sumatran; p(B) = 18%

G. Sumatran; p(B) = 25%; space = 115

Figure 17. Number of total births in the population in the past decade and projected mean number of births under alternate model scenarios. Projected results are averaged across 1000 model iterations.


ACKNOWLEDGEMENTS A meeting was conducted on June 19 2014 to discuss the Orangutan population and was attended by the following:

Brent Johnson, Population Biologist , Lincoln Park Zoo, [email protected]

Megan Elder, AZA Orangutan Animal Program Studbook Keeper, Como Park Zoo and Conservatory, [email protected]

Lauren Mechak, Assistant Population Biologist , Lincoln Park Zoo, [email protected]

Jennifer Michelberg, AZA Orangutan Population Advisor, [email protected]

Lori Perkins, AZA Bornean and Sumatran Orangutan SSP Coordinator, Zoo Atlanta, [email protected]

Adrienne Savrin, Research Assistant, Lincoln Park Zoo, [email protected]

Joseph L. Simonis, Post-doc at Alexander Center for Applied Population Biology, Lincoln Park Zoo, [email protected]

This report was also reviewed by:

Candice Dorsey, Director of Animal Programs, Association of Zoos and Aquariums, [email protected]

Megan Elder, AZA Orangutan Animal Program Studbook Keeper, Como Park Zoo and Conservatory, [email protected]

Lisa Faust, Vice President of Conservation and Science, Lincoln Park Zoo, [email protected]

Tracy Fenn, AZA Ape TAG Vice-Chair, Jacksonville Zoo and Gardens, [email protected]

Lauren Mechak, Assistant Population Biologist , Lincoln Park Zoo, [email protected]

Lori Perkins, AZA Bornean and Sumatran Orangutan SSP Coordinator, Zoo Atlanta, [email protected]

Adrienne Savrin, Research Assistant, Lincoln Park Zoo, [email protected]

Joseph L. Simonis, Post-doc at Alexander Center for Applied Population Biology, Lincoln Park Zoo, [email protected]

Tara Stoinski, AZA Ape TAG Chair, Zoo Atlanta, [email protected] If you have any questions about the report, please contact Lisa Faust at [email protected] Analyses in this report utilized the International Orangutan (Pongo pygmaeus + Pongo abelii) Studbook current to 26 April 2014 (Elder, 2014) and was performed using Poplink 2.4 and ZooRisk 3.8. Funding provided by Institute of Museum and Library Services (IMLS) LG-25-11-018 and MG-30-13-0065-13 to the Association of Zoos and Aquariums. Cover photo: courtesy of Megan Elder Citation: Johnson, B., Perkins, L., Elder, M., Stoinski, T., Fenn, T. Orangutan (Pongo pygmaeus + Pongo abelii) AZA Animal Program

Population Viability Analysis Report. Lincoln Park Zoo, Chicago, IL.

The contents of this report including opinions and interpretation of results are based on discussions between the project team

and do not necessarily reflect the opinion or position of Lincoln Park Zoo, Association of Zoos and Aquariums, and other

collaborating institutions. The population model and results are based on the project team’s best understanding of the

current biology and management of this population. They should not be regarded as absolute predictions of the population’s

future, as many factors may impact its future status.

mailto:[email protected]






LITERATURE CITED AZA Ape Taxon Advisory Group (TAG). 2014. Ape Advisory Group Regional Collection Plan (RCP) – 3rd Edition.

Ballou, J. D., and R. C. Lacy. 1995. Identifying genetically important individuals for management of genetic variation in pedigreed populations. Pages 76-111 in J. D. Ballou, M. Gilpin, and T. J. Foose, eds. Population Management for Survival and Recovery: Analytical Methods and Strategies in Small Population Conservation. Columbia University Press, New York. Ballou, J. D., and T. J. Foose. 1996. Demographic and genetic management of captive populations. Pages 263-283 in S. Lumpkin, ed. Wild Mammals in Captivity. University of Chicago Press, Chicago.

DeRose, M. A., and D. A. Roff. 1999. A comparison of inbreeding depression in life-history and morphological traits in animals. Evolution 53: 1288-1292. Earnhardt, JM, Bergstrom, YM, Lin, A, Faust, LJ, Schloss, CA, and Thompson, SD. 2008. ZooRisk: A Risk Assessment Tool. Version 3.8. Lincoln Park Zoo. Chicago, IL. Faust, LJ, Earnhardt, JM, Schloss, CA, and Bergstrom, YM. 2008. ZooRisk: A Risk Assessment Tool. Version 3.8 User’s Manual. Lincoln Park Zoo. Chicago, IL. Michelberg, J., Perkins, L., Elder, M. Orangutan (Pongo pygmaeus + Pongo abelii) AZA Species Survival Plan® Green Program

2014 Population Analysis and Breeding & Transfer Plan. AZA Population Management Center, Chicago, IL. Zoo Atlanta,

Atlanta, GA.

Elder, M. 2014. Orangutan (Pongo pygmaeus + Pongo abelii) AZA Studbook. Como Park Zoo and Conservatory, St. Paul, MN. Reed, D. H., and R. Frankham. 2003. Correlation between fitness and genetic diversity. Conservation Biology 17: 230-237.


DEFINITIONS Age Structure: A two-way classification showing the numbers or percentages of individuals in various age and sex classes. Current Gene Diversity (GD): The proportional gene diversity (as a proportion of the source population) is the probability that two alleles from the same locus sampled at random from the population will not be identical by descent. Gene diversity is calculated from allele frequencies, and is the heterozygosity expected in progeny produced by random mating, and if the population were in Hardy-Weinberg equilibrium. Founder: An individual obtained from a source population (often the wild) that has no known relationship to any individuals in the derived population (except for its own descendants). Inbreeding Coefficient (F): Probability that the two alleles at a genetic locus are identical by descent from an ancestor common to both parents. The mean inbreeding coefficient of a population will be the proportional decrease in observed heterozygosity relative to the expected heterozygosity of the founder population. Mean Kinship (MK): The mean kinship coefficient between an animal and all animals (including itself) in the living, zoo born population. The mean kinship of a population is equal to the proportional loss of gene diversity of the descendant (zoo born) population relative to the founders and is also the mean inbreeding coefficient of progeny produced by random mating. Mean kinship is also the reciprocal of two times the founder genome equivalents: MK = 1 / (2 * FGE). MK = 1 - GD. Mean Generation Time (T): The average time elapsing from reproduction in one generation to the time the next generation reproduces. Also, the average age at which a female (or male) produces offspring. It is not the age of first reproduction. Males and females often have different generation times. Percent Known: Percent of an animal's genome that is traceable to known Founders. Thus, if an animal has an UNK sire, the % Known = 50. If it has an UNK grandparent, % Known = 75% Population Viability Analysis (PVA): A PVA is a computer model that projects the likely future status of a population. PVAs are used for evaluating long-term sustainability, setting population goals, and comparing alternative management strategies. Several quantitative parameters are used in a PVA to calculate the extinction risk of a population, forecast the population’s future trajectory, and identify key factors impacting the population’s future. Potential Space: In the context of a Regional Collection Plan, the ‘potential space’ selected for each Program within the RCP, which may be based on available spaces for that species, desired spaces the TAG wishes to allocate, the size needed to maintain a viable population, or some combination of those factors. In the context of the ZooRisk modeling work, the potential space is a model parameter that can be set at any level, including the size listed in the RCP or a higher or lower size based on other criteria. Probability of Breeding [p(B)]: Female p(B) is the age-specific probability that a female will have at least one offspring in a year. For example, p(B) = 25% is equivalent to females producing an offspring once every 4 years. Within the reproductively viable age classes, all p(B) were set at a hypothetical constant value corresponding with an interbirth interval, which varied depending on the model scenario. Using a constant value means that all reproductively viable females would have the same chance of reproduction regardless of age. Qx, Mortality: Probability that an individual of age x dies during time period. Regional Collection Plan (RCP): document developed by Taxon Advisory Group (TAG) to describe species managed under their TAG, level of management with explanations, and evaluation of Target Population Sizes for each managed species. Risk (Qx or Mx): The number of individuals that have lived during an age class. The number at risk is used to calculate Mx and Qx by dividing the number of births and deaths that occurred during an age class by the number of animals at risk of dying and reproducing during that age class. The proportion of individuals that die during an age class is calculated from the number of animals that die during an age class divided by the number of animals that were alive at the beginning of the age class (i.e.-"at risk"). Stochastic Model: A model that includes random chance and variation in model parameters (e.g. randomly select if an individual will breed). Stochastic models will produce many different outcomes each time the model is run due to this variation. Models are typically run for many iterations to fully explore the trajectory a population might take. ZooRisk is a stochastic model. Taxon Advisory Group (TAG): There are several different TAGs and each oversees a broad group of animals (e.g. Antelope TAG, Small Carnivore TAG). Each TAG consists of several programs. The TAG contains experts including studbook keepers, program leaders, the TAG chair, and other advisors. TAGs evaluate the present conditions surrounding a broad group of animals (e.g., marine mammals) and then prioritize the different species in the group for possible captive programs.


APPENDICES

APPENDIX A. MODEL SETUP AND METHODS Analyses in this report were performed using PopLink 2.4, ZooRisk 3.8, and R statistical package. Complete documentation on

ZooRisk’s modeling approach and setup can be found in the software manual (Faust et al., 2008). These tables document the

basic file information (Table A1) key model variables, give some context for how ZooRisk utilizes them in the model and how

the PVA modeling team applies them, give values used in model scenarios, and describe data sources (Tables A2-A4).

Additionally, age and sex specific mortality rates are documented in Tables A5-A7.

For clarity, most figures in this report show the mean population size across multiple iterations. Model results such as mean

population sizes, levels of gene diversity (GD), and inbreeding (F) are averaged across 1000 model iterations; if some model

iterations go extinct, these values are only averaged over extant, surviving iterations. Where relevant, results are reported

on medium-term (25 year), and long-term (100 year) time frames. Results such as the probability of reaching the potential

space or extinction are based on the percentage of iterations that hit that target at least once over the 1000 years. Where

applicable, ± 1 standard deviation is included; large values represent wider variability in model results.

Table A1. Information regarding studbook utilization in PopLink 2.4 and ZooRisk 3.8.

File Information

Studbook Currentness Date 26 April 2014

Studbook Name Orangutan2014

Studbook Keeper for analytical database Megan Elder

Studbook Keeper for demographic database Megan Elder

ZooRisk Project Name Orangutan_2014 Table A2. Variable used in ZooRisk 3.8 scenarios for hybrid orangutans, including a description of each variable, the value, and the source.

Model Variable Description/Details of How Variable is Used in Model Value in Model Scenarios

Source

Demographic Settings

Living Population

ZooRisk uses a starting population to initiate each model scenario, incorporating data on each individual’s pedigree, age, sex, and reproductive status. Any animals unable to breed due to age, medical issues, or sterilizations can be designated as non-reproductive in the model, which removes them from the potentially breeding population. The model assumes that any new animals (either births or imports) are potentially reproductively viable; this may be an optimistic assumption.

See included individuals in Appendix B, Table B1

Studbook data; animals in AZA as of 27 Apr 2014, UDF: SP = X

Male and Female Age-Specific Mortality Rates (Qx)

Probability that an individual of age x dies during time period. Each year, the model stochastically determines whether each individual lives or dies based on that individual’s age- and sex-specific Qx.

See Table A5. No modifications were made from extracted Qx values.

Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = X

Infant Mortality Rates (Qx)

Mortality rate for infants 0-1 used in the model (as described above). Infant mortality is a vital rate that is sensitive to changes in husbandry and also may be a life stage that is vulnerable to inbreeding depression.

Male = 20% Female = 11%


Maximum Longevity

The maximum age individuals are allowed to live to in the model (if they haven’t died before that age). The model values were based on female SB# 942 and male # 941.

Male = 46 Female = 46


Reproductive Age Classes

Age classes in which females or males could potentially be paired for breeding in the model

Male 10 42 Female 1 42

Modeling team consulted the following sources: Program Leader, Studbook Keeper, Population Advisor

Annual Number of Offspring

When a female within the model is selected to reproduce in a given model year, ZooRisk uses these frequencies to stochastically determine the number of offspring she

1 offspring = 99% 2 = 1%



produces. Note that this distribution will be different than a litter size distribution if a species can have multiple clutches/litters within a year.

Birth Sex Ratio (BSR)

The model stochastically assigns a sex for any offspring created in the model. We extract historical studbook data and test for bias towards males or females in the sex ratio using a χ2 test. This evaluates whether the population is significantly different than 50% males, 50% females. For this population, the extracted birth sex ratio was not significantly biased. The extracted value was 0.5612 (χ

2 =

2.9388, df = 1, p > 0.05).

0.5 Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = X

Female Probability of Breeding [p(B)]

P(B) is the age-specific probability that a female will have at least one offspring in a year. For example, p(B) = 0.25 is equivalent to females producing an offspring on average once every 4 years, or 25% of reproductively available females breeding in any given year. Historical studbook data include many females who never had access to a male and were non-reproductive for management rather than biological reasons. It is difficult to use extracted p(B) data to determine what a population could do if all individuals were in breeding situations or the population was truly trying to increase reproduction. Because of this, model scenarios use simplified hypothetical levels of p(B) to evaluate the impact of changes in reproduction. To set the baseline p(B), we extracted the average number of births/year over the past decade from the studbook and identified a p(B) level in the model that would produce, on average, an equivalent number of projected births over the first 10 model years. Alternate scenarios used higher or lower p(B) levels. In the model, all p(B) were set at the same value within all female reproductive age classes. Using a constant value means that all reproductively viable females would have the same chance of reproduction regardless of age. This population produced 0 births/year on average over the past decade, which was used to calibrate the baseline p(B).

0.00


Genetic Settings

Genetic Management

ZooRisk can model a randomly breeding population or genetic management by mean kinship pairings and other genetic criteria, mimicking the way that AZA populations are managed to maintain gene diversity (GD) (Ballou & Lacy, 1995). This allows ZooRisk to more accurately project the amount of gene diversity retained through genetic management.

GM by mean kinship: ON

Modeling team decision

Inbreeding Depression

Inbreeding depression can be challenging to incorporate into PVA models because of uncertainty about which populations and life history traits will be affected, and at what inbreeding level they will become affected. Due to this uncertainty and since modeling inbreeding depression adds an additional layer of complexity to interpretation of results we have not included a “standard” inbreeding depression effect in the PVA models. The PVA includes management by mean kinship and measurements of final mean inbreeding levels to help users understand the potential future levels of inbreeding even with careful management. Readers should consider that model results

OFF Modeling team decision


may be optimistic if this species would be susceptible to inbreeding depression now or in the future.

Breeding group ratio

ZooRisk can simulate breeding groups of 1 male: multiple females. If a population has few reproductive-aged animals and/or very few breeding age males, this can impact demographic results by limiting the number of pairs/groups that can be formed. It can also impact genetic results, as it influences how pairings by mean kinship are made (see manual for more details).

1 male: 1 female


Number of Years Between Pairing

ZooRisk reshuffles the pairings with this frequency; a breeding group is left together for this number of years unless an individual group member dies, in which case another individual is shuffled in. A group is left together even if they may no longer be optimally paired by MK because of subsequent births.

28

Modeling team decision Modeling team consulted the following sources: Program Leader, Studbook Keeper, Population Advisor

Other Model Settings

Potential Space

ZooRisk has the option of including a space limitation on population growth. This limitation reduces breeding in the model population as it approaches the space limit, mimicking zoo management. For example, a Program Leader may begin to recommend fewer breeding pairs if available spaces for a population become limited. To determine an appropriate space limitation for the models, the PVA team, in consultation with the AZA Wildlife Conservation and Management Committee (WCMC), developed the approach of using the number of projected spaces in 5 years based on a Taxon Advisory Group’s (TAG) Regional Collection Plan (RCP). If that number is unavailable or unsuitable (i.e. if the population is already close to or larger than that space), the team will use the current population size + 10% or 10 individuals, whichever is greater. In some instances when more information is available, i.e. a more recent survey by the Species Coordinator, we will use this value.

None Modeling team decision

Approach to space limit

The model can allow the population to grow/decline immediately to its space limit (if birth rates will allow it), but it is more likely that increases/decreases in space will occur gradually as new institutions join or leave a program.

Approach space limit gradually over 5 years


Number of Years How far into the future the model projects. 100 Modeling team decision

Number of Iterations

Since stochastic models have inherent variation, each model run (or iteration) will produce a slightly different population trajectory, and the model is run many times to reflect the full potential variation a population could experience.

500 Modeling team decision

Extinction Threshold

Size at which the population will be considered extinct. 0 Modeling team decision

Importations/ Exportations

ZooRisk can model removal or addition of individuals into the population. An importation event will bring a specific number of individuals (of a specified sex and age) that are completely unrelated to the current population (potential founders) into the population in a specified year. These might be individuals coming from the wild or from non-AZA institutions in other regions or in North America.

Exportations can be used to model reintroductions into the wild or transfer of individuals outside of the AZA population. ZooRisk can model two types – a simple export that selects a specific number of individuals of the designated sex and age classes in the specified year, or a threshold export that will select the 'extra' individuals above some threshold to export in the specified year.

0 imports and 0 exports

Studbook data, filters = AZA, 1 Jan 2004 1 Dec 2013, UDF: SP = X


Table A3. Variable used in ZooRisk 3.8 scenarios for Bornean orangutans, including a description of each variable, the value, and the source.


Source


Living Population

ZooRisk uses a starting population to initiate each model scenario, incorporating data on each individual’s pedigree, age, sex, and reproductive status. Any animals unable to breed due to age, medical issues, or sterilizations can be designated as non-reproductive in the model, which removes them from the potentially breeding population. The model assumes that any new animals (either births or imports) are potentially reproductively viable; this may be an optimistic assumption.

See included individuals in Appendix B, Table B2

Studbook data; animals in AZA as of 27 Apr 2014, UDF: SP = B




Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = B





Maximum Longevity

The maximum age individuals are allowed to live to in the model (if they haven’t died before that age). The model value for female was based on SB#s 449, 660, and 510, all of which are dead. The value for males was estimated in consultation with population managers.


Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = B Modeling team consulted the following sources: Program Leader, Studbook Keeper, Population Advisor






When a female within the model is selected to reproduce in a given model year, ZooRisk uses these frequencies to stochastically determine the number of offspring she produces. Note that this distribution will be different than a litter size distribution if a species can have multiple clutches/litters within a year.

1 offspring = 99% 2 = 1%




2 =

2.9388, df = 1, p > 0.05).

0.5 Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = B


P(B) is the age-specific probability that a female will have at least one offspring in a year. For example, p(B) = 0.25 is equivalent to females producing an offspring on average once every 4 years, or 25% of reproductively available females breeding in any given year. Historical studbook data include many females who never had access to a male and were non-reproductive for management rather than biological reasons. It is difficult to use extracted p(B) data to determine what a population could do if all individuals were in breeding situations or the population was truly trying to increase reproduction. Because of this, model scenarios use simplified hypothetical levels of p(B) to evaluate the impact of changes in

0.115 (Baseline) Alternate scenarios = 0.19, 0.25

Studbook data, filters = AZA, 1 Jan 2004 1 Dec 2013, UDF: SP = B


reproduction. To set the baseline p(B), we extracted the average number of births/year over the past decade from the studbook and identified a p(B) level in the model that would produce, on average, an equivalent number of projected births over the first 10 model years. Alternate scenarios used higher or lower p(B) levels. In the model, all p(B) were set at the same value within all female reproductive age classes. Using a constant value means that all reproductively viable females would have the same chance of reproduction regardless of age. This population produced 2.7 births/year on average over the past decade, which was used to calibrate the baseline p(B).

Genetic Settings

Genetic Management





Inbreeding depression can be challenging to incorporate into PVA models because of uncertainty about which populations and life history traits will be affected, and at what inbreeding level they will become affected. Due to this uncertainty and since modeling inbreeding depression adds an additional layer of complexity to interpretation of results we have not included a “standard” inbreeding depression effect in the PVA models. The PVA includes management by mean kinship and measurements of final mean inbreeding levels to help users understand the potential future levels of inbreeding even with careful management. Readers should consider that model results may be optimistic if this species would be susceptible to inbreeding depression now or in the future.




1 male: 1 female




28








Potential Space

ZooRisk has the option of including a space limitation on population growth. This limitation reduces breeding in the model population as it approaches the space limit, mimicking zoo management. For example, a Program Leader may begin to recommend fewer breeding pairs if available spaces for a population become limited. To determine an appropriate space limitation for the models, the PVA team, in consultation with the AZA Wildlife Conservation and Management Committee (WCMC), developed the approach of using the number of projected spaces in 5 years based on a Taxon Advisory Group’s (TAG) Regional Collection Plan (RCP). If that number is unavailable or unsuitable (i.e. if the population is already close to or larger than that space), the team will use the current population size + 10% or 10 individuals, whichever is greater. In some instances when more information is available, i.e. a more recent survey by the Species Coordinator, we will use this value. The 2007 Ape TAG RCP set the desired spaces for Bornean orangutans over 4 years old at 85. However, animals younger than 4 hold spaces in the model, and some more spaces may become available for Bornean orangutans if the population grows slightly.

100 Alternate scenario = 115








Importations/Exportations

ZooRisk can model removal or addition of individuals into the population. An importation event will bring a specific number of individuals (of a specified sex and age) that are completely unrelated to the current population (potential founders) into the population in a specified year. These might be individuals coming from the wild or from non-AZA institutions in other regions or in North America. Exportations can be used to model reintroductions into the wild or transfer of individuals outside of the AZA population. ZooRisk can model two types – a simple export that selects a specific number of individuals of the designated sex and age classes in the specified year, or a threshold export that will select the 'extra' individuals above some threshold to export in the specified year.

p(B) calibration = Imports: 1:1 ratio of males to females ages 10-30, mimicking amounts from the past decade: 2009- 4 Scenarios = 0 imports and 0 exports

Studbook data, filters = AZA, 1 Jan 2004 1 Dec 2013, UDF: SP = B Modeling team consulted the following sources: Program Leader, Studbook Keeper, Population Advisor

Table A4. Variable used in ZooRisk 3.8 scenarios for Sumatran orangutans, including a description of each variable, the value, and the source.


Source


Living Population

ZooRisk uses a starting population to initiate each model scenario, incorporating data on each individual’s pedigree, age, sex, and reproductive status. Any animals unable to breed due to age, medical issues, or sterilizations can be designated as non-reproductive in the model, which removes them from the potentially breeding population. The model assumes that any new animals (either births or imports) are potentially reproductively viable; this may be

See included individuals in Appendix B, table B3

Studbook data; animals in AZA as of 27 Apr 2014, UDF: SP = S


an optimistic assumption.




Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = S





Maximum Longevity

The maximum age individuals are allowed to live to in the model (if they haven’t died before that age). The model value for female was based on SB#s 3 and 366, both of which are dead. The value for males was estimated in consultation with population managers.









When a female within the model is selected to reproduce in a given model year, ZooRisk uses these frequencies to stochastically determine the number of offspring she produces. Note that this distribution will be different than a litter size distribution if a species can have multiple clutches/litters within a year.

1 offspring = 99% 2 = 1%




2 =

3.2190, df = 1, p > 0.05).

0.5 Studbook data, filters = AZA, 1 an 1 8 27 Apr 2014, UDF: SP = S


P(B) is the age-specific probability that a female will have at least one offspring in a year. For example, p(B) = 0.25 is equivalent to females producing an offspring on average once every 4 years, or 25% of reproductively available females breeding in any given year. Historical studbook data include many females who never had access to a male and were non-reproductive for management rather than biological reasons. It is difficult to use extracted p(B) data to determine what a population could do if all individuals were in breeding situations or the population was truly trying to increase reproduction. Because of this, model scenarios use simplified hypothetical levels of p(B) to evaluate the impact of changes in reproduction. To set the baseline p(B), we extracted the average number of births/year over the past decade from the studbook and identified a p(B) level in the model that would produce, on average, an equivalent number of projected births over the first 10 model years. Alternate scenarios used higher or lower p(B) levels. In the model, all p(B) were set at the same value within all female reproductive age classes. Using a constant value means that all reproductively viable females would have

0.148 (Baseline) Alternate scenarios = 0.18, 0.25

Studbook data, filters = AZA, 1 Jan 2004 1 Dec 2013, UDF: SP = S


the same chance of reproduction regardless of age. This population produced 2.8 births/year on average over the past decade, which was used to calibrate the baseline p(B).

Genetic Settings

Genetic Management





Inbreeding depression can be challenging to incorporate into PVA models because of uncertainty about which populations and life history traits will be affected, and at what inbreeding level they will become affected. Due to this uncertainty and since modeling inbreeding depression adds an additional layer of complexity to interpretation of results we have not included a “standard” inbreeding depression effect in the PVA models. The PVA includes management by mean kinship and measurements of final mean inbreeding levels to help users understand the potential future levels of inbreeding even with careful management. Readers should consider that model results may be optimistic if this species would be susceptible to inbreeding depression now or in the future.




1 male: 1 female




31



Potential Space

ZooRisk has the option of including a space limitation on population growth. This limitation reduces breeding in the model population as it approaches the space limit, mimicking zoo management. For example, a Program Leader may begin to recommend fewer breeding pairs if available spaces for a population become limited. To determine an appropriate space limitation for the models, the PVA team, in consultation with the AZA Wildlife Conservation and Management Committee (WCMC), developed the approach of using the number of projected spaces in 5 years based on a Taxon Advisory Group’s (TAG) Regional Collection Plan (RCP). If that number is unavailable or unsuitable (i.e. if the population is already close to or larger than that space), the team will use the current population size + 10% or 10 individuals, whichever is greater. In some instances when more information is available, i.e. a more recent survey by the Species Coordinator, we will use this value.

100 Alternate scenario = 115



The 2007 Ape TAG RCP set the desired spaces for Bornean orangutans over 4 years old at 85. However, animals younger than 4 hold spaces in the model, and some more spaces may become available for Sumatran orangutans if the population grows slightly.











Importations/Exportations

ZooRisk can model removal or addition of individuals into the population. An importation event will bring a specific number of individuals (of a specified sex and age) that are completely unrelated to the current population (potential founders) into the population in a specified year. These might be individuals coming from the wild or from non-AZA institutions in other regions or in North America. Exportations can be used to model reintroductions into the wild or transfer of individuals outside of the AZA population. ZooRisk can model two types – a simple export that selects a specific number of individuals of the designated sex and age classes in the specified year, or a threshold export that will select the 'extra' individuals above some threshold to export in the specified year.

p(B) calibration = 1:1 ratio of males to females ages 10-30, mimicking amounts from the past decade: Imports: 2009- 1 2010- 1 Exports: 2004- 1 2005- 1 Scenarios = 0 imports and 0 exports

Studbook data, filters = AZA, 1 Jan 2004 1 Dec 2013, UDF: SP = S Modeling team consulted the following sources: Program Leader, Studbook Keeper, Population Advisor

Table A5. Male and female mortality rates used in all hybrid orangutan scenarios of the ZooRisk model are listed below. Each year, the model determines whether each individual lives or dies stochastically based on that individuals age- and sex- specific mortality rate. Male Female

Age(x) Qx Number at Risk Age(x) Qx Number at Risk

0 0.2 118 0 0.11 96

1 0 92.5 1 0.11 83.5

2 0 91 2 0 87

3 0 93 3 0 91

4 0 93 4 0 90

5 0 96 5 0 91

6 0 101 6 0 95

7 0.04 100 7 0 98

8 0.04 97 8 0 100

9 0 94 9 0 100

10 0 97 10 0 102

11 0.04 94 11 0 99

12 0 91 12 0 101

13 0.12 95 13 0 104

14 0.05 91 14 0.04 103

15 0 89 15 0.04 97

16 0.05 90 16 0 102

17 0 92 17 0.04 106

18 0 92 18 0 99

19 0 88 19 0 97

20 0 88 20 0 102

21 0 84 21 0 105

22 0.05 81 22 0 104


23 0 78 23 0 101

24 0 78 24 0 106

25 0 76 25 0 105

26 0 72 26 0 104

27 0 66 27 0 102

28 0.08 64 28 0 102

29 0 52 29 0.05 100

30 0 50 30 0 93

31 0 50 31 0 84

32 0 49 32 0 77

33 0 42 33 0.07 70

34 0 38 34 0 59

35 0.12 31 35 0 56

36 0.2 24 36 0 54

37 0 17 37 0 48

38 0 14 38 0.12 43

39 0 11 39 0 39

40 0 8 40 0 35

41 0 8 41 0 33

42 0 6 42 0 31

43 0 3 43 0 27

44 0 2 44 0 24

45 0 1 45 0 20

46 1 1 46 1 15

47 0 11

48 0 11

49 0 9

50 0 9

51 0 8

52 0 7

53 0 4

54 0 3

55 0 2

56 0 2

57 0 1 Table A6. Male and female mortality rates used in all Bornean orangutan scenarios of the ZooRisk model are listed below. Each year, the model determines whether each individual lives or dies stochastically based on that individuals age- and sex- specific mortality rate. Male Female


0 0.25 118 0 0.13 96

1 0 92.5 1 0.03 83.5

2 0.03 91 2 0 87

3 0 93 3 0.02 91

4 0.03 93 4 0 90

5 0.03 96 5 0.02 91

6 0 101 6 0 95

7 0 100 7 0.02 98

8 0.03 97 8 0 100

9 0 94 9 0 100

10 0 97 10 0.03 102

11 0.07 94 11 0 99

12 0.04 91 12 0 101

13 0 95 13 0 104

14 0 91 14 0 103

15 0.04 89 15 0 97

16 0.04 90 16 0 102

17 0 92 17 0.03 106

18 0.06 92 18 0 99


19 0.07 88 19 0 97

20 0.07 88 20 0 102

21 0.07 84 21 0.03 105

22 0 81 22 0.03 104

23 0 78 23 0.06 101

24 0.03 78 24 0.03 106

25 0.04 76 25 0 105

26 0.04 72 26 0 104

27 0.08 66 27 0.03 102

28 0.05 64 28 0.03 102

29 0.1 52 29 0 100

30 0.11 50 30 0.09 93

31 0.06 50 31 0.07 84

32 0.06 49 32 0 77

33 0.21 42 33 0.04 70

34 0.18 38 34 0 59

35 0.12 31 35 0 56

36 0.16 24 36 0.06 54

37 0.2 17 37 0.06 48

38 0.5 14 38 0.07 43

39 0.5 11 39 0.08 39

40 0 8 40 0.09 35

41 0 8 41 0 33

42 0 6 42 0.2 31

43 1 3 43 0.12 27

44 0 24

45 0.31 20

46 0.25 15

47 0 11

48 0 11

49 0 9

50 0 9

51 0 8

52 1 7 Table A7. Male and female mortality rates used in all Sumatran orangutan scenarios of the ZooRisk model are listed below. Each year, the model determines whether each individual lives or dies stochastically based on that individuals age- and sex- specific mortality rate. Male Female


0 0.23 127 0 0.22 101

1 0.05 98.5 1 0 87.5

2 0 97 2 0 91

3 0 99 3 0 95

4 0 99 4 0 94

5 0 102 5 0 95

6 0 107 6 0 99

7 0.05 106 7 0 102

8 0.03 102 8 0.03 104

9 0.03 97 9 0 104

10 0 99 10 0.02 106

11 0.05 95 11 0 103

12 0 92 12 0.02 104

13 0.03 96 13 0.05 107

14 0 92 14 0.07 106

15 0.03 90 15 0 100

16 0 91 16 0 105

17 0.05 94 17 0.05 109

18 0 93 18 0 102

19 0.06 89 19 0 100


20 0.12 89 20 0 105

21 0.03 85 21 0.02 108

22 0.04 82 22 0.05 106

23 0.04 79 23 0 103

24 0 79 24 0.04 109

25 0.07 78 25 0.02 108

26 0.07 74 26 0.02 107

27 0.04 68 27 0.02 105

28 0.04 66 28 0 105

29 0 54 29 0.02 102

30 0 52 30 0.05 95

31 0 52 31 0.03 86

32 0.17 51 32 0.09 79

33 0 43 33 0.07 72

34 0.17 39 34 0 61

35 0.15 32 35 0 58

36 0.09 25 36 0 56

37 0.1 18 37 0.04 50

38 0 15 38 0 45

39 0.25 12 39 0.05 41

40 0 9 40 0 37

41 0.33 9 41 0.05 35

42 0 7 42 0 32

43 0.33 4 43 0 28

44 0.5 3 44 0.06 25

45 0 2 45 0.15 21

46 0 2 46 0 16

47 0 1 47 0 12

48 0 1 48 0.25 11

49 0 1 49 0 9

50 1 1 50 0 9

51 0.2 8

52 0 7

53 0.25 4

54 0 3

55 0 2

56 0.5 2

57 1 1


APPENDIX B. INCLUDED INDIVIDUALS As of April 26, 2014 (the studbook currentness date):

The Hybrid Orangutan population consisted of 45 individuals (21 males, 24 females, 0 unknown) (Table B1).

The AZA Bornean Orangutan population consisted of 84 individuals (33 males, 51 females, 0 unknown) (Table B2). Five

individuals are excluded from the breeding population. Those animals with “Allowed to Breed = NO” hold space but are never

eligible for reproduction. This leaves a potentially breeding population of 79 (33.46.0) individuals.

The AZA Sumatran Orangutan population consisted of 85 individuals (36 males, 48 females, 1 unknown) (Table B3).

Seventeen individuals are excluded from the breeding population. Those animals with “Allowed to Breed = NO” hold space

but are never eligible for reproduction. This leaves a potentially breeding population of 68 (34.33.1) individuals.

Table B1. Individuals included in the starting Hybrid population

Studbook ID Sex % Known Age Institution Allowed to Breed Reason For Exclusion

1018 Neutered Female

100 44 LITTLEROC NO Hybrid

1182 Male 100 42 TOLEDO NO Hybrid

1196 Female 100 42 SEATTLE NO Hybrid


100 41 HOUSTON NO Hybrid


100 41 NZP-WASH NO Hybrid


100 40 FORTWORTH NO Hybrid


100 39 BUSCH TAM NO Hybrid

1504 Neutered Male

100 38 DENVER NO Hybrid


100 37 ST PAUL NO Hybrid




100 36 HONOLULU NO Hybrid

1614 Neutered Male

100 36 HOUSTON NO Hybrid

1616 Neutered Male

100 36 INDIANAPL NO Hybrid

1617 Neutered Male

100 36 ATLANTA NO Hybrid

1723 Neutered Male

100 35 LOSANGELE NO Hybrid


100 34 INDIANAPL NO Hybrid

1756 Neutered Male

100 34 HONOLULU NO Hybrid


100 33 NORFOLK NO Hybrid


100 33 MILWAUKEE NO Hybrid


1872 Neutered Male

100 32 MILWAUKEE NO Hybrid


100 31 LEON NO Hybrid


1886 Neutered Male

100 31 NORFOLK NO Hybrid


100 31 FRESNO NO Hybrid

1972 Female 100 30 INDIANAPL NO Hybrid

1973 Female 100 28 RACINE NO Hybrid



100 29 FT WAYNE NO Hybrid


100 29 LEON NO Hybrid

2021 Neutered Male

100 28 LITTLEROC NO Hybrid

2064 Neutered Male

100 28 RACINE NO Hybrid

2066 Neutered Male

100 27 WAHPETON NO Hybrid

2121 Female 100 27 NZP-WASH NO Hybrid

2127 Neutered Male

100 26 WACO NO Hybrid

2132 Neutered Male



100 26 LOUISVILL NO Hybrid

2139 Neutered Male

100 26 LOUISVILL NO Hybrid


2255 Neutered Male

100 25 SEATTLE NO Hybrid

2431 Neutered Male

100 23 CHICAGOBR NO Hybrid

2655 Male 100 20 INDIANAPL NO Hybrid

2905 Neutered Male

100 15 BUSCH TAM NO Hybrid

3331 Male 100 9 INDIANAPL NO Hybrid

941 Neutered Male

100 46 SEATTLE NO Hybrid


Table B2. Individuals included in the starting Bornean population


449 Female 100 52 CHICAGOBR NO Age

660 Female 100 52 SANDIEGOZ NO Age

971 Female 100 45 LOSANGELE NO Age; Health

1387 Female 100 39 COLUMBUS YES


100 37 KANSASCTY NO Sterile

1621 Female 100 36 ROCHESTER YES

1635 Male 100 36 BUSCH TAM YES

1640 Female 100 36 TOLEDO YES

1671 Male 100 35 CHICAGOBR YES

1683 Female 100 35 JACKSON YES

1704 Female 100 35 PHOENIX YES

1753 Female 100 34 LOWRY YES

1789 Female 100 33 BUSCH TAM YES

1793 Female 100 33 HOUSTON YES

1813 Female 100 33 PITTSBURG YES

1817 Female 100 33 CHICAGOBR YES

1824 Female 100 33 LOSANGELE YES

1865 Neutered 100 32 TOPEKA NO Sterile


Female


2023 Male 100 28 JACKSON YES


2037 Female 100 28 TOPEKA YES

2048 Female 100 29 KANSASCTY YES

2062 Male 100 28 ERIE YES

2063 Male 100 28 CLEVELAND YES

2083 Female 100 27 CLEVELAND YES

2120 Male 100 27 PHOENIX YES

2175 Male 100 25 KANSASCTY YES

2176 Male 100 25 WACO YES

2201 Male 100 25 TOPEKA YES

2270 Male 100 24 GREENVISC YES

2274 Male 100 24 TOLEDO YES

2354 Male 100 24 HOGLE YES

2374 Female 100 23 GREENVISC YES

2379 Female 100 23 HOGLE YES

2500 Female 100 22 ATLANTA YES

2503 Female 100 22 ERIE YES

2602 Male 100 21 OMAHA YES


2626 Male 100 20 COLUMBUS YES

2658 Male 100 19 COLO SPRG YES

2755 Female 100 17 COLO SPRG YES

2757 Male 100 17 NZP-WASH YES

2758 Female 100 17 NZP-WASH YES

2801 Female 100 16 BUSCH TAM YES


2852 Female 100 15 WACO YES


2902 Male 100 14 KANSASCTY YES

2906 Male 100 14 LOWRY YES

2908 Female 100 14 OMAHA YES

2923 Female 100 14 NORFOLK YES

3000 Female 100 13 MADISON YES




3054 Male 100 11 ROCHESTER YES



3105 Male 100 10 HOUSTON YES

3108 Male 100 10 ATLANTA YES

3151 Male 100 10 MADISON YES



3201 Female 100 9 TOPEKA YES

3203 Female 100 8 HOGLE YES


3251 Male 100 8 PITTSBURG YES

3252 Male 100 8 GREENVISC YES

3253 Female 100 8 PHOENIX YES


3255 Male 100 8 PHOENIX YES




3335 Female 100 5 CHICAGOBR YES



3370 Male 100 4 ERIE YES




3536 Female 100 0 ROCHESTER YES



Table B3. Individuals included in the starting Sumatran population


366 Female 100 57 SEDGWICK NO Age

433 Female 100 54 PORTLAND NO Age

881 Female 100 46 OKLAHOMA NO Age

915 Neutered Female

100 46 DENVER NO Age; Sterile

1020 Female 100 44 ST LOUIS YES

1042 Female 100 44 RIO GRAND NO Age; Sterile

1044 Female 100 50 BROWNSVIL NO Age; Sterile

1100 Female 100 43 FRESNO YES

1106 Female 100 43 ATLANTA NO Age

1145 Male 100 42 ATLANTA NO Age; Sterile

1164 Female 100 47 TORONTO YES

1209 Female 100 42 SACRAMNTO NO Age

1455 Female 100 38 FORTWORTH NO Health

1529 Male 100 37 ROLLING H YES

1576 Female 100 36 MEMPHIS NO Behavior

1587 Female 100 36 BROWNSVIL YES


1714 Male 100 34 RIO GRAND YES

1765 Female 100 34 ROLLING H NO Sterile

1773 Male 100 33 BIRMINGHM YES

1841 Female 100 32 COLUMBUS NO Health

1850 Female 100 32 SEDGWICK YES

1882 Male 100 31 MEMPHIS YES

1904 Female 100 32 BIRMINGHM YES


1926 Female 100 30 RIO GRAND YES

1932 Male 100 30 DENVER YES

1971 Male 100 29 FRESNO YES

1980 Female 100 29 LOUISVILL YES

2015 Female 100 29 METROZOO YES

2016 Female 100 29 CINCINNAT NO Management exclusion

2018 Male 100 28 ST PAUL YES


2034 Male 100 28 EL PASO YES

2069 Male 100 27 FT WAYNE YES

2070 Female 100 27 SANDIEGOZ YES

2116 Female 100 27 ST PAUL YES

2131 Female 100 26 COLO SPRG YES

2137 Male 100 26 LOUISVILL YES

2157 Female 100 25 AUDUBON YES

2161 Female 100 25 DENVER YES



2400 Male 100 23 CINCINNAT YES

2419 Female 100 22 EL PASO YES

2501 Male 100 22 METROZOO YES



100 21 SANDIEGOZ NO Sterile

2509 Male 100 21 ST LOUIS NO Behavior


2517 Female 100 21 PHILADELP YES

2604 Male 100 21 AUDUBON YES


100 20 RIO GRAND NO Sterile

2706 Male 100 19 SANDIEGOZ YES

2708 Female 100 19 FT WAYNE YES

2718 Male 100 18 SEDGWICK YES

2726 Male 100 18 PHILADELP YES


2802 Female 100 16 MEMPHIS YES

2958 Male 100 13 OKLAHOMA YES

3006 Male 100 12 INDIANAPL YES


3100 Male 100 11 SACRAMNTO YES


3152 Male 100 10 ST LOUIS YES

3167 Female 100 9 ST LOUIS YES

3202 Male 100 9 BROWNSVIL YES

3257 Male 100 7 TORONTO YES



3333 Male 100 6 ST PAUL YES


3347 Female 100 5 RIO GRAND YES

3351 Female 100 4 AUDUBON YES

3373 Female 100 4 PHILADELP YES

3395 Female 100 3 DENVER YES

3397 Male 100 3 FRESNO YES



3432 Male 100 2 SEDGWICK YES

3450 Female 100 2 BIRMINGHM YES


35171 Male 100 1 BROWNSVIL YES


3535 Male 100 1 RIO GRAND YES

3547 Female 100 0 SANDIEGOZ YES 1Individual with unknown sex that was randomly assigned a sex.


APPENDIX C. RISK CATEGORIES AND RESULTS ZooRisk uses five standardized risk tests to evaluate different aspects of a population’s demography, genetics, and

management that might put the population at risk (Table C1). The ZooRisk development team and members of the AZA small

Population Management Advisory Group (SPMAG) worked to develop the cutoff for each test. For a given scenario, the

overall risk level is based on the most severe score received among the tests. This approach standardizes assessments across

species and allows managers to compare species programs using the same framework.

For a given scenario, the overall risk level is based on the most severe score it achieved for any of the five tests. Tests 2-4 are

based on the population’s history, and are the same across all model scenarios. For the Orangutan Animal Programs, the risk

levels showed some variation among scenarios (Table C2). The goal for managers should be to move the population from a

Critical status towards a Low Risk status, utilizing some of the management tactics highlighted in the model results.

Table C1: Standardized Risk Test, reflecting the population’s status in zoos and aquariums. Tests Low Risk (LR) Vulnerable (V) Endangered (E) Critical (C)

Probability of extinction in 100 years, based on PVA

0 - 9% 10 - 15% 20 - 49% 50 - 100%

Number of zoos with breeding-aged mixed-sex groups in current population

>3 Zoos 3 Zoos 2 Zoos 1 Zoo

Number of breeding-aged animals (m.f); based on current population

>10.10 7.7 to 10.10 4.4 to 6.6 0.0 to 3.3

Reproduction in the last generation, based on historical studbook data

>9 pairs reproducing 6-9 pairs reproducing 3-5 pairs reproducing 0-2 pairs reproducing

GD of starting population and/or population in 100 years based on PVA

Starting: > 0.9 100 yrs: > 0.9

Starting: 0.8 – 0.9 100 yrs: 0.75 – 0.9

Starting: 0.75 – 0.8 100 yrs: 0.5 – 0.75

Starting: < 0.75 100 yrs: < 0.5

Table C2: Detailed risk results for the population model scenarios.

Scenario

Individual Risk Score for Each Test

OVERALL RISK SCORE FOR

EACH SCENARIO (HIGHLIGHTED)

Probability of

extinction

Number of zoos

Breeding Groups

Breeding in Last Gen.

GD

B Bornean baseline; p(B) = 11.5% LR LR LR LR V LR V E C

C Bornean open; p(B) = 19% LR LR LR LR LR LR V E C

D Bornean; p(B) = 25%; space = 115

LR LR LR LR LR LR V E C

E Sumatran baseline; p(B) = 14.8% LR LR LR LR LR LR V E C

F Sumatran; p(B) = 18% LR LR LR LR LR LR V E C

G Sumatran; p(B) = 25%; space = 115

LR LR LR LR LR LR V E C

orangutan€¦ · if the aza bornean orangutan population continues its current breeding rate (2.7...

Documents