Distribution and predation of diamondback terrapin nests at six upland islands of Jamaica Bay Wildlife Refuge and Sandy Hook Unit, Gateway National Recreation Area.
M.S. Thesis. Hofstra University
Sylwia Elizabeth Ner. 2003
Abstract
Northern diamondback terrapins, Malaclemys terrapin terrapin, are declining in number throughout their range as a result of habitat degradation and urbanization. Human activities have altered habitat and predator-prey relationships. Recent increases in raccoon populations play a significant role in limiting terrapin numbers.
I studied predation rates on terrapin nests in 2000 and 2001 at the Jamaica Bay Unit (JBU), Staten Island Unit (SIU), and, in 2002, at the Sandy Hook Unit (SHU) of Gateway National Recreation Area (GNRA) in New York and New Jersey. Most of my research was conducted on six of the islands of JBU (Canarsie Pol, Elder’s Point, Little Egg Marsh, Pumpkin Patch, Ruffle Bar, and Subway Island) and SHU of NJ. On Canarsie Pol, Little Egg Marsh, and Ruler’s Bar, (total of 192.8 ha) approximately 20 nests/year are deposited and about 318 hatchlings are produced annually. Predators destroyed approximately 32.6% (14/43) of nests; additional natural causes, (e.g. flooding, infertility, and maggots) caused 14.7% (55/373) of eggs to fail to hatch, yielding egg viability as 86.3% (322/373). No predation occurred on Canarsie Pol, probably due to the very low number of nesting females.Other islands in JBU--Elder’s Point, Pumpkin Patch, and Subway Island--not appear to have terrapin nesting in 2000 nor 2001. Mammal and bird surveys on RB and LEM showed that few possible turtle predators are present on these islands. Smaller islands may be an important recruitment source of Jamaica Bay’s terrapin population, whereas RBH now may be a sink population.
At the SHU, predation and egg viability rates were similar to those in RBH. I found 203 nests in eight different locations.
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