Dissertation Defense AnnouncementCollege of Arts and Sciences announces the Final Dissertation Defense of
Malle Carrasco-Harrisfor the Degree of Doctor of Philosophy
March 06, 2020 at 10:00 AM, Life Sciences Room - 415
Advisor: Judith A. Cole
The spatial ecology and genetics of copperhead snakes (Agkistrodon contortrix) in an urban forest
ABSTRACT: As global population increases and metropolitan areas grow, natural habitats are progressively fragmented, isolated, and modified. Species residing in urban areas face novel challenges compared to conspecifics in undisturbed habitats. Animals in and around urban areas often modify behavior and space use to reduce anthropogenic disturbance. Further, populations may be isolated from other suitable habitats, potentially reducing opportunities to mate with non-related individuals. Although the consequences of urbanization have been extensively studied in birds and mammals, less is known about limited mobility animals, such as reptiles. Reptiles, specifically snakes are particularly vulnerable in urban areas because of their decreasing populations, restricted dispersal across anthropogenic environments, specific habitat and thermal requirements, and human persecution. Thus, we examined the spatial ecology and genetics of Copperhead Snakes (Agkistrodon contortrix) in an urban forest fragment and a rural location in Shelby County, TN. We collected morphological data, and radio tracked snakes during the active season to estimate movement parameters and habitat use. We found copperheads in the urban forest were smaller, but similar in body condition compared to rural conspecifics. The urban snakes also exhibited reduced home range sizes and movement parameters compared to rural subjects. Snakes in the urban forest did not alter movement based on trails, but home range size was positively related to average distance to the trail. We created a resource utilization function to model urban snake habitat use, and our results suggest canopy cover, log number, and log distance were important in predicting habitat use. Finally, we examined population genetics using microsatellite loci markers. We found urban snakes had decreased measures of genetic diversity compared to rural individuals, and identified significant population differentiation between the two groups. We did not find evidence of inbreeding for either population. This case study indicates the urban population of copperheads alters spatial behavior and has reduced genetic diversity compared to the rural population. Further work should be done in other disturbed natural areas to investigate the effects of urbanization on reptiles, and provide land managers with the information necessary to maintain areas that are conducive to both biological diversity and human recreation.