Hawkbill Sea Turtle Thesis

• Thesis
• The Hawksbill Sea Turtle will become extinct with the rising temperature cause by the changes in our climate.
• Taxonomy o Kingdom: Animalia o Phylum: Chordata o Class: Reptilla o Order: Testudines o Family: Cheloniidae o Genus: Eretmochelys o Species: imbricate o (NOAA 2005) http://www.nmfs.noaa.gov/pr/species/turtles/hawksbill.html#taxonomy
• Distribution o Found in the tropical regions of the globe o Inhabit the Atlantic, Pacific, and Indian Oceans
 “Hawksbills are believed to inhabit coastal waters in more than 108 countries” (eol.org) o They will return to the beaches which they were born
 “Hawksbill nesting occurs in at least 70 countries” (eol.org) o Hawksbills stay in the warmer waters near the equator o Travel long distances for breeding/laying eggs
• Habitat
o Mature Adults o Weigh up to 154 pounds (eol.org) o Tend to stay off the coast of sandy beaches o The hawksbill is a migratory species
 Move from breeding areas to feeding/hunting areas o Depth range: 0-300 meters (eol.org) o Stay near the rocky bottom of the ocean
 Reefs, “lagoons of oceanic islands, and continental shelves” (eol.org) o Prefer deeper waters o Juveniles o Stay in shallower waters o Will travel in sargassum to keep safe o They will surround coral reefs or rocky bottoms
 “sea grass, algal beds, or mangrove bays and creeks or mud flats” (eol.org)
• Environmental Conditions o Ideal temperatures: 7.560-28.819 (Celcius) (eol.org) o Salinity (PPS): 33.277-37.155 (eol.org) o Areas where vegetation grows o Not open ocean (thus coral reefs = protection)
• Prey o Uses sharp beak to help eat o (Bjorndal 1997)
 Manatee grass (Syringodium filiforme)
 Microdictyon sp.
 Woody plant remains
 Goose barnacles
 Fish
eggs
 Tunicate
 Crab chela
 Algae o Sponges
 “Intestinal contents of hawksbills typically consisted of masses of dissociated spicules” (Meylan 1998)
 “…A type of glass” (Meylan 1998)
• Predators o Mature Adults
 (Leighton 2008)
• “mongooses prey on hawksbill sea turtle”
 (NOAA 2005)
• Sharks o Juveniles and Eggs
 (NOAA 2005)
 Ghost crabs
 Raccoons
 Skunks
 Opossums
 Mongooses
 Dogs
 Seabirds
 Fish
• Outside threats o Humans
 Bycatch
 Nesting destruction
 Hatchlings being drawn away from the ocean (lights)
 Wanting the shells for displays
 Want the eggs for consumption
 Meat consumption in parts of the world
• Main topic #1: Hatchling survival o (Kamel et al 2005)
 The sea turtles will be forced to nest higher up on the beach due to the limited beach access from sea level rise.
• The more the sea level will rise then
• (Fish et al 2007) o “If beaches did not shift at all in response to sea-level changes, an average 26% of the beach area would be lost”
 Nests at a higher location on the beach will have a lower survival rate than those closer to the water.
 (Poloczanska et al 2009)
• “egg relocation” o The scientists have begun taking the sea turtle eggs from unsafe and unhealthy beaches and placing them at safer beaches to increase survival rate.
 The juveniles will be more vulnerable if they cannot find the warm currents to help navigate them to safer habitats once they reach the size needed.
 (Zimmer and Emlen 2016)
• The turnover rate for the hatchlings would show more hatchlings making it to adulthood which means less prey they feed on.
• The other aspect would be more prey as the hatchlings are consumed by predators in the area of the beach.
• Main topic #2: Changes in sand and water temperature o (Kamel et al 2005)
 “show temperature-dependent sex determination”
 (Zimmer and Emlen 2016)
• According to chapter 11, the operation sex ratio is “the ratio of male to female individuals who are available for reproducing at any given time”. o The ratio is primarily around 1:1, however, changes in temperature causes less females to give birth or less males to fertilize the eggs. o Temperature of the beach can change the sex ratio o (Mrosovsky and Provancha 1991)
 Hot temperatures show more females
 Cold temperatures show more males
 Believe nesting time periods changes will cause extinction o (Pike 2013)
 Depth of the hole can determine sex
• Too shallow = too hot (female)
• Too deep = too cold (male) o Temperature will cause either more females or more males depending if the sand is warmer or colder
 Placement of the nest determines sex
• Higher on the beach with more vegetation would lower sand temperature
• Lower on the beach with less vegetation would increase the sand temperature o (Hoegh-Guldberg and Bruno 2010) o The warming of the ocean waters will slowly result in a decrease in deepwater currents. o “The uneven distribution of heating also strongly influences the behavior of ocean currents”
 Hawksbills sea turtles will use the warm surface currents to migrate to find suitable habitats.
 If the warm currents begin to disappear then the adult sea turtles will struggle to migrate to nesting beaches and habitats.
• Main Topic #3: Adult Beach Nest Choice o (Hawkes et al 2009)
 The Hawksbill sea turtle prefer beaches which include:
• Need space above high tide
• Beach vegetation
• Females preference where to lay her eggs
 Changes
• Increase temperature could “facilitate year-round nesting”
• Sand will be too hot
• Nests will be higher on the beach than normal o (Kamel et al 2005)
 “nest placement is of great importance”
• Nest placement will determine “her fitness, mainly through the survival of her offspring”
 Nests too close to the water will be destroyed
 Nests too far increases predator’s likelihood of getting a hatchling o (Zimmer and Emlen 2016)
 Based on chapter 11, the direct benefits can help the female sea turtles with the nesting.
• For the females who focus on their eggs and wanting them to survive, her “choices increase [her] fitness directly”.
• Main topic #4: Reproduction due to habitat changes o (Kuffner et al 2007)
 “The only way to slow or prevent the continuing acidification of surface ocean waters is to reduce the emissions of CO2 from human activities to the atmosphere”
 Hawksbill sea turtle habitat, coral reefs, will change drastically due to acidification which will slowly cause the death of the reef. o The changes the coral reef will go through could cause the hawksbill to move towards open ocean to feed. o The open ocean would cause an increase in human and predators interaction which could cause fatalities. o White Oaks/Evolutionary Biology Class
 The open ocean could cause sea turtles to not find their mates as often thus possibly decreasing the amount of production.
• Based off the White Oaks Plantation trip with Capstone as well as evolutionary biology class articles, if a species does not mate as often the species will suppress the gene these urges and use the energy into feeding o Evolutionary Biology
 (Zimmer and Emlen 2016)
 The sea turtles could also fall into a bottleneck as the Hawksbill sea turtles in one habitat are reduced to do a lack of resources
• This would cause differences in genetic variation.
 From chapter 6, the sea turtles could find themselves in the situation of inbreeding depending on where they find their new habitat and the population size of that area.
• Inbreeding depression could arise from the sea turtles as they will pass on the recessive traits which will affect their overall fitness.