The Physiological Effects of Relocation on Gopher Tortoises (Gopherus polyphemus)
Type of DegreeDissertation
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As a result of habitat destruction throughout the southeastern United States, gopher tortoises (Gopherus polyphemus) have experienced an 80% decrease in their populations in the past 100 years. To protect the remaining gopher tortoises from extinction, populations are often relocated to safer habitats. However, the long-term evaluations that are necessary to determine relocation success cannot reasonably be conducted for this long-lived species because it would require decades of data collection. Immediate measures of relocation success involving the use of physiological biomarkers are thus required because such indicators can be measured in the short-term and provide a more relevant assessment of the health and viability of relocated populations. Physiological biomarkers that could contribute to determining relocation success include measures of corticosterone and adrenal competence, reproductive health, and immune function. I first conducted a validation study to establish proper dosages and timings for these biomarkers in gopher tortoises. I then conducted a study which determined that trapping, handling, and various manipulations to gopher tortoises do not cause them stress, as indicated by a lack of change in corticosterone levels and movement patterns between the pre- and post-protocol periods. Subsequently, I relocated tortoises at Ft. Benning, Georgia and assessed each of the biomarkers prior to and again 30 days and 10 months post-relocation. I found no changes in baseline corticosterone levels as a result of relocation. However, the relocators showed a significantly stronger response to the ACTH challenge post-relocation in spring indicating that they, and not the residents, may have experienced an acute stress response after being relocated in spring, but the response likely occurred prior to the 30 day measure. There was no effect of relocation on sex steroid levels or on immune function. However, I did find that using the ELISA as a measure of disease status is ineffective and unreliable since titers change rapidly and drastically in less than 30 days. Finally, I found that none of the variables that I measured showed any effect from pre- to post-relocation according to habitat quality. Ultimately, it appears that relocation does not result in direct physiological detriment to gopher tortoises at the specific time points that I measured. However, removing this keystone species from its environment could have irreparable consequences for the commensal and obligate species that are left behind.