Graduate Student Research

Comparison of viability rates, hatchling survivorship, and sex ratios of laboratory – and field incubated nests of the estuarine, emydid turtle Malaclemys terrapin.
M.S. Thesis. Hofstra University.
Maria Rosaria Giambanco

Abstract

Malaclemys terrapin, a member of family Emydidae, is one of only a few turtle species worldwide that lives in estuaries, and the only such turtle that inhabits the coastal United States. Diamondback terrapins feed primarily on mollusks and crustaceans. Due to their active foraging and mobility, terrapins are crucial macro-consumers in the estuarine ecosystems. Gateway National Recreation Area (GNRA), a large estuarine park east of the mouth of the Hudson River, NY has a large terrapin population. Due to habitat loss elsewhere, parks such as GNRA, are vital to the preservation of M. terrapin. Although terrapin numbers are declining throughout their range, the Jamaica Bay Wildlife Refuge (a unit of GNRA) population is still impressively large. Therefore it is vital to document the current viability rates, hatchling survivorship, and sex ratios of the JBWR population. I found that 46.1% of protected nests laid in JBWR were predated by raccoons despite the use of nest protectors, and 2.9% of the undisturbed nests were flooded . The average clutch size for terrapin nests (including protected nests and nests found post-hatching) over both years was 11.8 eggs. Egg viability for field-incubated nests was 88.6%, and 86.7% of the non-predated eggs resulting in hatchlings that emerged from the nest successfully (= emergence success). The viability rate for laboratory-incubated nests was 89.7%. Viability rates varied with incubation temperature, as did post-hatchling mortality and hatchling sex ratios. Sex ratios of laboratory incubated turtles varied with incubation temperature. At 26,28,30,32 and 34 oC the sex ratio of hatchlings was 100, 93.3, 11.1, 0 and 7.7% respectively.