Maternal Effects and Offspring Behavior: Potential Contributors to the Lack of Recruitment in Mississippi Gopher Tortoises (Gopherus polyphemus)
type: CreativeWork
description: Federally threatened in Mississippi, gopher tortoise (Gopherus polyphemus) populations within the state have strongly variable recruitment and are generally in decline. Hatching success is significantly lower in Mississippi than in any other part of the species’ range , and most hatchlings die within the first year. There are few refuges where survival and hatching success is high. Here I compare two populations that differ in recruitment and offspring survival for differences in corticosterone. Corticosterone is a hormone that influences both energy availability and is released in elevated levels during stressful events, like living in poor quality habitat. Prolonged corticosterone elevation can impede growth and immune responses and result in early death. To assess adult stress, I utilized leukocyte profiles as they are influenced by prolonged elevation of corticosterone. A viable yolk sampling technique was used to collect yolk samples to determine levels of yolk CORT. Hatchlings were then kept in captivity for two years to observe growth rates and burrowing behavior before being released and monitored via radiotelemetry to monitor dispersal and survival. I found no differences in adult stress or egg yolk CORT between populations. This suggests adults are not excessively stressed. Survival of hatchlings did not differ between sites. Captive-reared hatchlings were larger and may have better survival than similar aged wild hatchlings. Overall, the poor survival of gopher tortoises may be more strongly linked to environmental variables such as soil structure than physiological ones.
abstract: Federally threatened in Mississippi, gopher tortoise (Gopherus polyphemus) populations within the state have strongly variable recruitment and are generally in decline. Hatching success is significantly lower in Mississippi than in any other part of the species’ range , and most hatchlings die within the first year. There are few refuges where survival and hatching success is high. Here I compare two populations that differ in recruitment and offspring survival for differences in corticosterone. Corticosterone is a hormone that influences both energy availability and is released in elevated levels during stressful events, like living in poor quality habitat. Prolonged corticosterone elevation can impede growth and immune responses and result in early death. To assess adult stress, I utilized leukocyte profiles as they are influenced by prolonged elevation of corticosterone. A viable yolk sampling technique was used to collect yolk samples to determine levels of yolk CORT. Hatchlings were then kept in captivity for two years to observe growth rates and burrowing behavior before being released and monitored via radiotelemetry to monitor dispersal and survival. I found no differences in adult stress or egg yolk CORT between populations. This suggests adults are not excessively stressed. Survival of hatchlings did not differ between sites. Captive-reared hatchlings were larger and may have better survival than similar aged wild hatchlings. Overall, the poor survival of gopher tortoises may be more strongly linked to environmental variables such as soil structure than physiological ones.
author: Holbrook, Aaron L
keywords: Gopher tortoise, Gopherus polyphemus, hatchlings, leukocyte profiles, yolk corticosterone, Animal Sciences, Biology, Other Animal Sciences
date published: 2015-12-01T08:00:00Z
date modified: 2026-07-24T05:44:34Z
provider: University of Southern Mississippi
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Southern Mississippi