Social structure and habitat preferences of moose population in Biebrza National Park

Mammal Research Institute, Polish Academy of Sciences, BiałowieżaProject: Biodiversity protection of Red Bog (Czerwone Bagno) - relic of raised bogs in Central Europe

Włodzimierz JędrzejewskiBogumiła JędrzejewskaTomasz BorowikKris HundertmarkMarcin Górny

Biebrza National Park

Biebrza Moose Data

• Observations by park personnel– group size and composition– location– date

• 1998-2010 (most from Sept. 2006-February 2010)• 1534 observations• 2770 total moose• Classified as adult male, adult female, juvenile, or calf• 2041 adults of known sex

Sexual segregation• Sexes use different areas/habitats outside of the mating season

• Common in ungulates with body-size dimorphism

– Larger difference in body size is associated with more extreme sexual segregation

• Some hypotheses (among others)

– Predator avoidance by females and calves

• Females choose less risky environments whereas males choose riskier environments to gain back

condition after breeding season

– Food selection

• Females (smaller body size) seek out high-quality forage

• Males (larger body size) seek out more abundant but more fibrous forage due to their gut

morphology

– Activity budget

• Larger-bodied males spend more time ruminating and less time feeding than

smaller-bodied females and therefore can’t synchronize movements

Moose group dynamics• Group size: mean = 1.6 (SD 1.3), range = 1—20 • Adult males: 1—11• Adult females: 1—8 • 67% of all observations are singletons (cows with calves

included)

Group type for multi-adult groupsG = 1.76, p = 0.18

Month; LS Means

Vertical bars denote 0.95 confidence intervals

1 2 3 4 5 6 7 8 9 10 11 12

Month

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

Gro

up s

ize

F = 4.68, p < 0.0001

Open Closed

Season Mean SD Mean SD t P(1-tailed)

Spring 1.89 1.33 1.79 1.14 -0.69 0.25

Summer 1.42 1.20 1.45 1.09 0.18 0.43

Fall 1.68 1.83 1.47 1.07 -1.67 0.048

Winter 1.74 1.05 1.44 0.89 -2.55 0.0055

Group size by habitat closure by season (α’ = 0.0127)

Are the sexes distributed differently across the landscape?

• Create 2041 random points within the park

• Compare with 2041 observations of adults

• Tested moose locations vs. random locations– Dispersion significantly different (p < 0.0001)

• Tested males vs. females seasonally– Šidák correction for multiple comparisons: α’ =

0.0127– Winter (21 Oct.—30 Apr.) p < 0.0001 – Spring (1 May—30 June) p = 0.011– Summer (1 July—20 Sept.) p = 0.005– Rut (21 Sept.—20 Oct.) p = 0.35

Are the sexes distributed differently across the landscape?

Social segregation

• Measured by social segregation coefficient– Varies from 0 (complete aggregation) to 1

(complete segregation)

What habitat characteristics are driving the segregation of the sexes?

• Classify observations by habitat characteristics• Account for potential location error

Forest

Meadow

100 m

• Classify observations by habitat characteristics• Account for potential location error• Characterize random points in the same manner

to represent available habitat• Randomly assign a sex to each random point• Use stepwise logistic regression to identify

factors influencing space use

What habitat characteristics are driving the segregation of the sexes?

Possible predictors

Landscape metrics• Distance to road• Distance to village• Distance to arable land• Distance to railway• Distance to forest edge• Distance to marsh/water

• Year• Season

Habitat metrics• Deciduous forest

• Coniferous forest

• Other forest

• Marsh

• Meadow

• Arable land/orchard

• Wetland (yes/no)

• Edge (yes/no)

Temporal metrics

How do moose respond to those factors?

Selection coefficients

• = (use – availability)/(use + availability)• – 1 (complete avoidance) to +1 (complete preference)

*

*

*

*

Habitat selection

* Males ≠ females

*

* *

*

*

**

*Males ≠ females

Importance of marsh to calving• 16 May-15 June• 90% of all female locations in marsh• 50% of all male locations in marsh (40% in

deciduous forest)Use

Selection during calving

What patterns are there in space use that could lead to segregation?

– Use variables identified by logistic regression– Test sex × location (random vs. observed)– Test sex × season × location

observed random

deciduousconiferous

F F MM

"Season2"*Location*Sex; LS Means

Wilks lambda=.99120, F(21, 11659.)=1.7117, p=.02232

Effective hypothesis decomposition

Vertical bars denote 0.95 confidence intervals

Location: Observed

Season2:Winter

CalvingSummer

Breed1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

dis

t ro

ad

Location: Random

Season2:Winter

CalvingSummer

Breed

F M

observed random

Dis

tan

ce

to

ro

ad

FM

wintercalving

summerbreeding

wintercalving

summerbreeding

"Season2"*Location*Sex; LS Means

Wilks lambda=.99120, F(21, 11659.)=1.7117, p=.02232

Effective hypothesis decomposition

Vertical bars denote 0.95 confidence intervals

Location: Observed

Season2:Winter

CalvingSummer

Breed-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

con

ifero

us

fore

st

Location: Random

Season2:Winter

CalvingSummer

Breed

F M

observed random

co

nif

ero

us

fore

st

wintercalving

summerbreeding

wintercalving

summerbreeding

FM

"Season2"*Location*Sex; LS Means

Wilks lambda=.99120, F(21, 11659.)=1.7117, p=.02232

Effective hypothesis decomposition

Vertical bars denote 0.95 confidence intervals

Location: Observed

Season2:Winter

CalvingSummer

Breed-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

de

cid

uo

us

fore

st

Location: Random

Season2:Winter

CalvingSummer

Breed

F M

observed random

de

cid

uo

us

fo

res

t

wintercalving

summerbreeding

wintercalving

summerbreeding

FM

wintercalving

summerbreeding

wintercalving

summerbreeding M

F

Dis

tan

ce

to

fo

rest

ed

ge

observed random

Conclusions

• Group size in Biebrza moose is small• Group size in open habitats is greater than in closed habitats,

particularly in winter• Mixed-sex groups are not common, males and females are equally

solitary• Moose in Biebrza segregate outside of the breeding season on a

very fine scale• In general, open habitats were avoided and forested habitats were

selected• Males have a higher preference for deciduous forest in winter and

summer and are farther from roads• Females have a higher preference for coniferous forest in winter

and are closer to roads• Females use coniferous forest more in winter than do males• Marsh habitat, although generally avoided, is very important during

the calving season

Thank you