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Individual study: Translocation leads to restoration of an extirpated red-sided garter snake Thamnophis sirtalis parietalis population near Inwood, Manitoba, Canada

Published source details

Macmillan S. (1995) Restoration of an extirpated red-sided garter snake Thamnophis sirtalis parietalis population in the interlake region of Manitoba, Canada. Biological Conservation, 72, 13-16


Demand for red-sided garter snakes Thamnophis sirtalis parietalis for the pet trade has led to high collection pressure. Populations are especially vulnerable at traditional hibernation sites where thousands of individuals may gather. Regulations in Manitoba (Canada) restrict collection at hibernacula to 2 weeks in September, but there were no restrictions on numbers taken. As a result many populations were severely depleted or extirpated. This experiment attempted to reinstate a population (extirpated by unusually heavy spring flooding in 1974) near the village of Inwood in southern Manitoba.

During autumn (11 September-20 October) 1985, 720 snakes (451 male, 269 female) were taken from a population gathering at a hibernation site 55 km north of Inwood. These were released at the extirpated hibernaculum. To enable individual recognition, snakes were marked before release by clipping ventral scales. Snakes were periodically recaptured and released in the spring and autumn of the subsequent three years to monitor the population.

In spring 1986, 84 of the 720 translocated snakes (12%) were recaptured at the hibernaculum, indicating that it had been successfully used as an over-winter hibernation site. In autumn 1986, only one translocated snake was recaptured (a male) but sampling was disrupted by snake collectors. It is assumed that some snakes were either removed by collectors and/or had dispersed to other dens in the area. Additionally, 107 ‘new’ snakes (unmarked individuals not from the original translocation) were recorded.
In spring 1987, again only one translocated snake (a male) was recaptured but 27 new snakes (26 male, 1 female) were recorded.
In spring 1988, 427 individuals were recorded (410 male; 17 female) but none were from the original translocation. Mark and recapture indicated an estimated population of 800 (almost entirely ‘new’) snakes using the hibernacula. It is thought that snakes from other hibernation sites in the area may have been attracted by the presence of the translocated snakes, perhaps following scent trails.
Thus, although this study has not shown that translocation on its own was successful in garter snakes reoccupying an extirpated hibernaculum, it may usefully play a role in doing so.
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