Date of Award

2021

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Department

Biological Sciences

First Advisor

Nancy E. Karraker

Abstract

Diamondback terrapins (Malaclemys terrapin) require estuarine habitats for most aspects of their life cycles. However, adult female terrapins nest in coastal uplands, and hatchling terrapins use upland habitats following nest emergence. In these upland areas, hatchlings are particularly vulnerable to mortality risks from coastal land management activities such as mowing and tilling. From 2019 to 2021, we used small tracking devices to monitor hatchling movements and habitat use at a wildlife refuge in Rhode Island. When hatchlings emerged from nests in late summer and early fall, we attached a radio transmitter and passive integrated transponder (PIT) tag (n=46) or only a PIT tag (n=132) to hatchling carapaces. From August to June, we tracked the hatchlings via radio telemetry and a sweeping PIT tag antenna. While 53.4% of hatchlings (n=95) had unknown fates when hatchlings’ overwintering sites were not located or tags detached, 46.6% of hatchlings (n=83) had known fates. Known fates included 49 predated hatchlings, 3 unknown causes of death, as well as 23 hatchlings who overwintered in the upland and 11 hatchlings who moved to the salt marsh in the fall. In the uplands, hatchlings typically overwintered within about two meters of habitat edges and disproportionately overwintered in brushland habitat. Hatchling movement activity peaked from late August to early October, then ceased until hatchlings re-emerged in late April through early June. Hatchlings lost body mass during the overwintering period. Following fall nest emergence, most hatchlings dispersed toward the southwest of the study area with about 68% of hatchlings dispersing generally toward water and 32% of hatchlings dispersing generally away from water. The divergent patterns we observed in overwintering habitat use by hatchlings may be related to an evolutionary transition or phenotypic plasticity. We recommend limiting use of heavy equipment near habitat edges where hatchlings tend to overwinter, and timing habitat management activities during colder months (November to March) when hatchlings tend to be inactive. By implementing these strategies when managing coastal uplands and salt marshes, we can reduce human impacts on hatchlings and better conserve diamondback terrapins and their habitats.

Available for download on Thursday, January 05, 2023

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