FW364 Ecological Problem Solving

Lab 7: Loggerhead turtle conservation

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Outline for Today

Lab 7: Investigate loggerhead turtle conservation strategies

A. Determine baseline population growthB. Comparison of turtle conservation strategies

Loggerhead Turtle BackgroundA little big about loggerhead turtles…

World’s largest hard-shelled turtle: average size ~35” and 300 lbs Long-lived (47-67 yrs) with delayed sexual maturity (17-33 yrs)Broadly distributed: Found in Atlantic, Pacific, and Indian oceansEndangered species

Causes of decline:Mortality: Over-harvest (intentional harvest) By-catch by commercial fisheries Eating trash

Reduced fecundity: Loss of nesting habitat Introduction of exotic nest predators

e.g. Red fox in Australia

Subject of intense conservation efforts

Tracks for nineleatherback turtles

Loggerhead Turtle Background

Undergo large migrations

Illustrate wide movement patterns of sea turtles

Africa

South America

NorthAmerica

Europe

Turtle Conservation

To reduce turtle by-catch in shrimp fisheries, fishermen are required to include turtle excluder devices (TEDs) in their nets

TEDs are the primary management tool for reducing adult mortality

hawksbill turtle

Turtle Conservation

lost habitat

existing habitat

Dramatic sea turtle nesting habitat loss

green turtle

Conservation efforts:Protecting nesting beachesProtecting nestsTransplanting eggs to hatcheries

Loggerhead Turtle Stages

Five stages:

(0) Hatchlings(1) Small juveniles(2) Large juveniles(3) Subadults (i.e., small adults)(4) Adults

0 0 0 4.665 61.8960.675 0.703 0 0 0

0 0.047 0.657 0 00 0 0.019 0.682 00 0 0 0.061 0.8091

4F

HatchlingsSmall

Juveniles01S 12S 23S 34SSubadults Adults

3F

Large Juveniles

33S 44S22S11S

Loggerhead Leslie matrix (from textbook):

Lab 7 – Loggerhead Turtle Conservation

Goal:

Use a stage model to evaluate twoalternative conservation strategies:

Increasing adult survival vs. adult fecundity

Two parts:

A. Determine baseline population growthB. Comparison of turtle conservation strategies

Part A: Determine baseline population growth for loggerhead turtles

Lab 7 – Loggerhead Turtle Conservation

Run a stage-structured simulation (see lab manual for parameters) and determine:

Final population size (total number of turtles)

Part B: Comparison of turtle conservation strategies

Lab 7 – Loggerhead Turtle Conservation

Compare cost-effectiveness of two management strategies:

1. Use of TEDs to increase survival rates of subadult and adult turtles2. Protection of nesting beaches and transplanting eggs to hatcheries to

increase subadult and adult fecundities

Givens:

3. Increasing the three subadult and adult survival rates (33S, 34S, 44S) by 1% costs the fishermen $10,000

4. Increasing both subadult and adult fecundity rates (3F, 4F) by 1% costs taxpayers $2,500

Assumptions:

Assumption about demographic stochasticity

Assumption about density dependence

Assumptions motivating your recommendations to policy makers(e.g., assumptions about human behavior,who should pay for conservation efforts,

right to impose conservation costs on particular groups vs. sharing costs)

Lab 7 – Loggerhead Turtle Conservation