LE3 .A278 1994

1994

Herman, Tom

Acadia University

Master of Science

Masters

Biology

Biology

Parks Canada - Halifax Defence Complex is committed to developing George's Island as an historic site. Despite its low species diversity the island supports an unusually dense and morphologically diverse population of Thamnop his sirtalis pallidulus (Maritime Garter Snakes). Three hundred and ninety-one snakes were marked from May to October 1993. Movement and activity patterns were similar to those observed in other populations of garter snakes. The total male:female ratio was 0.8:1 with an estimated density of 90 juveniles and adults per hectare. Predation is limited and occurs primarily in spring; low levels of human induced mortality occur throughout summer. As a probable result of this relaxed predation pressure, George's Island Maritime Garter Snakes have become docile: during handling only three percent of encounters included biting and 50% of encounters showed no or only a delayed anti-predator response. Morphologically the George's Island population is unusual: it contains melanistic and partly melanistic individuals (5 of 394 observations) and an unusually high number (48%) of individuals with abnormally shaped and or divided ventral and or subcaudal scales. Adults on George's Island appear slightly smaller than mainland adults; however, the George's Island population is reproducing successfully despite a less diverse diet than is available to its mainland counterparts. Preliminary genetic analysis indicates that of eleven enzymes examined there is one fixed allele for Mannose-6-phosphate Isomerase and statistically insignificant variation from mainland Nova Scotia in the frequency of the two alleles that code for Phosphogluconate Dehydrogenase. Recommendations for minimizing the impact of development on the island include -redirecting proposed trails away from important garter snake sites and educating the public. Moni taring of snake populations should provide a gauge of long-term human impacts on the island.

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