An update from Antigua and new NCSU graduate student Andrew Maurer. Thanks Andrew!
Hatchling season is upon us on Long Island, Antigua. Nests that we saw deposited 50-60 days ago are hatching, often multiple in a night. It usually happens so fast we only see the tracks they leave behind. Seeing tiny hawksbill hatchlings leaves no doubt about it, this is about as charismatic as megafauna can get. Here’s some quick relevant info:
- Hawksbills have the highest number of eggs per clutch among marine turtles, with an accepted average clutch size of 130 eggs for the species. They also have the smallest hatchlings.
- Clutch sizes here on Long Island average out to closer to 150, and typically start higher and then taper off during the course of the nesting season and over the 3-6 clutches a female will lay in that season.
- Incubation duration is typically 55-60 days, and is correlated with incubation temperature. Higher temperatures are associated with lower incubation durations.
- Marine turtles have temperature-dependent sex determination (TSD), and higher temperatures produce more females.
- Hatchlings will hatch underground, maneuver out of their shells, and then wait to emerge en masse. This usually happens at night and is thought to be triggered by a drop in sand temperature.
- We calculate hatch success (eggs that hatch / total clutch size) and emergence success (hatchlings that leave the egg chamber / total clutch size) by excavating nests after they hatch. We count egg shells, rescue any unlucky or trapped hatchlings, and determine the fate of unhatched eggs.
- Average hatch success here in 2014 was 82%, resulting in an estimated ~38,000 hatchlings. Hopefully 2015 is just as successful, though we probably won’t reach that hatchling output (last year had a record number of nests).