Saving the Loggerheads

By Brian Vajanaphanich and Sean Wang

Loggerhead Background

• Most abundant marine turtle in the U.S.• Live from 47-67 years• Grow up to 3 feet• Females lay ~80 eggs/year• Females start laying eggs at 22

Loggerhead Problems

• Nesting habitat destruction• Human lighting directing hatchlings away from

ocean• Turtles caught in fish nets• Population declining

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Loggerhead Options

• Maintaining nesting habitat• Implementation of Turtle Excluder Device on

fish nets

Loggerhead Egg Saving

• Egg mortality rates can sometimes reach 95%• Human affects on turtles cause babies/eggs to

– Crawl the wrong way when trying to enter the water for the first time

– Be crushed under human activity on beaches• The average mortality rate for turtle babies

and eggs is ~32.53%

Loggerhead TED

• Tens of thousands of turtles per year are killed by bottom trawling fishing nets

• The main victims of fishing nets are turtles aged between 9-16 years old

• TEDs(Turtle Exclusion Devices) allow turtles to pass through fishing nets without being trapped and killed

Loggerhead Simulation

• Leslie matrix used to model population• Estimated 55 year survival

Age(Years)

Survival Rate(%/year)

Fecundity(Eggs/year)

1 .6747 0

2-8 .7857 0

9-16 .6758 0

17-22 .7425 0

23-55 .8091 80

Loggerhead Population

• Under current conditions the population is expected to drop by ~3% annually

Eigenvalues/Eigenvectors

• When a square matrix is multiplied by a vector, the resulting vector is a scalar multiple of the original vector

• There are as many possible eigenvalues as the number of rows and columns in the matrix

• Eigenvalues>1 show growth, <1 show death

Loggerhead R Coding

• Created a 55 by 55 matrix that updated the population vector.

• Graphed the population over time• Calculated and graphed the eigenvalue at

different survival rates

Loggerhead Option 1

• We can increase the survival rate of 0-1 year olds (eggs/babies)

Loggerhead Option 2

• We can increase the survival rate of 9-16 year olds by implementing TEDs

Loggerhead Solution• If TEDs can raise the survival rates of 9-16 year

olds by at least ~6.6% then the Loggerhead Turtles will be saved.

Loggerhead TED Talk

• TEDs are estimated to reduce mortality rates from trawling nets by 97%

• Only reduces shrimp catch by 5-13%• Relatively cheap to implement.

High Fives Only!!!!!

Acknowledgements• Crouse, Deborah T., Larry B. Crowder, and Hal

Caswell. "A Stage-Based Population Model for Loggerhead Sea Turtles and Implications for Conservation." Ecology 68.5 (1987): 1412-423. Jstor. Ecological Society of America, 07 Apr. 2008. Web. 30 July 2015.

• Shiffman, David. "Turtle Excluder Devices: Analysis of Resistance to a Successful Conservation Policy." Southern Fried Science. Southern Fried Science, 07 Jan. 2011. Web. 30 July 2015.

• William Cuello, Robert Guy, Timothy Lewis, Sebastian Schreiber, King David, and William Cuello

https://www.youtube.com/watch?v=jRFaEYn2fOc&feature=youtu.be

Turtle Movie