Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

2007

Thesis Director

Stephen Mullin

Thesis Committee Member

Robert Fischer

Thesis Committee Member

Thomas Nelson

Abstract

Several reptile species have populations that are in decline, and anthropogenic habitat loss and alteration are arguably the factors having the greatest impact on these species. More attention has been paid to understanding the activity season habitat needs in snakes than on the habitat requirements for overwintering. I examined the patterns of both activity season and overwintering habitat use by a population of northern watersnakes (Nerodia sipedon) that inhabit an artificial levee in central Illinois. My research objectives were to determine how a population of northern watersnakes uses an artificial levee during the activity season and to determine what type of habitat this population uses as hibernation sites to better understand their overwinter ecology. The study site was Lake Charleston, a man-made reservoir separated from the Embarras River by a levee system. Surveys for N. sipedon were made in Spring of 2006 and again in Spring 2007. All snakes encountered were individually marked and measured. Fourteen adult snakes were surgically implanted with radiotransmitters and tracked during the 2006 activity season until hibernation and again in Spring 2007 following emergence. Using the minimum convex polygon method, the mean home range size for the 12 snakes was 1.63 ± 0.65 ha. For seven snakes, the mean 50% kernel home range was 0.21 ± 0.05 ha and the mean 95% kernel home range size was 1.16 ± 0.30 ha. For a subset of snakes, the mean body temperature during the activity season was significantly different from mean ambient air temperature. Nine snakes overwintered in non-active crayfish burrows. Five of these sites were on the river side ofthe levee, the remaining sites were on the east side of the Embarras River. The mean temperatures within the hibernation sites were more stable compared to ambient air temperatures during winter, and did not fall below 0 °C. Understanding all aspects of a species' ecology, including overwintering ecology, can help identify the factors that make the species susceptible to habitat loss and fragmentation. This is crucial in limiting the impacts of future habitat alterations within a species' range.

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