All ETDs from UAB

Advisory Committee Chair

Thane Wibbels

Advisory Committee Members

Ken Marion

David Owens

Document Type

Thesis

Date of Award

2015

Degree Name by School

Master of Science (MS) College of Arts and Sciences

Abstract

The Kemp’s ridley sea turtle is currently listed as critically endangered, and has a very limited range, often found along the Atlantic coast though primarily inhabiting the Gulf of Mexico, with the majority of all nesting occurring near Rancho Nuevo, Mexico. Historically, large numbers of turtles have been reported to nest at Rancho Nuevo; though numbers dropped due to egg take and by-catch in the fishing and shrimping industries. Extensive conservation efforts over the last several decades significantly increased the number of nests; however the recovery status of the Kemp’s ridley is still in question, and the continued research and conservation efforts at the nesting beach are vital to this species. The aim of the current study is to further understand the vital hatchling life history stage, focusing on emergence from the nest followed by sea-finding orientation. Emergence was documented to occur later than those times reported by studies of other species, and could be attributed to a number of proximate and ultimate characteristics which may have selected for these times. The specific threshold temperature hypothesis for emergence was not supported by this study; however, the decreasing thermal gradient hypothesis was support, suggesting this may be a cue utilized by hatchlings during emergence. Additionally, results of sea-finding orientation indicated hatchlings were more efficient with a tighter orientation patter in locations with distinctly contrasting horizon silhouettes (versus locations with reduced contrast in the landward and seaward directions), suggesting this contrast may be a strong cue utilized during orientation. Further, under conditions of reduced horizon contrast, light availability appeared to have a stronger effect on orientation. This suggests that conservation programs which re-locate nests should move those nests and/or release hatchlings at locations with strongly contrasting horizon silhouettes to help facilitate efficient sea-finding following emergence. The overall results of this study suggest hatchlings utilize multiple orientation systems over a short period of time, and though the relationship between these systems has not been extensively investigated, it may be important for hatchlings to undergo all of these stages, as collectively these systems may have evolved to enhance survival during these early life history stages.

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