In the spring, snakes emerge from the dens and breed in the
area immediately surrounding the den sites. As each female emerges
from the dens they are vigorously pursued by a number of males
that entwine themselves around her forming a mating ball. Adult
females are easily recognized, as they are larger in both length
and thickness than adult males. In late summer the young are born,
a female may give birth to as many as 40-50 young with the average
brood being about 20 in number. Most juvenile snakes tend to remain
where they spent the summer, seeking refuge in anthills, animal
burrows or any crevasse that will take them below the frost line.
In their second year they will migrate to an established den site.
It is thought that snakes locate their home den using a scent trail.
Most adult snakes use the same den site year to year, however, mark
recapture studies have shown that some snakes use alternate dens.
The movement of so many snakes to and from the winter den area
has often resulted in significant mortality along Provincial Trunk
Highway #17 adjacent to the Narcisse Snake
Dens. Growing concern over
the level of mortality led to an innovative solution to reduce the problem.
In 2000, the Narcisse Snake Mortality Advisory Group forged a partnership
with Manitoba Hydro, Centra Gas and a number of other businesses,
organizations and volunteers to install a series of small tunnels
under the highway and erect barrier fencing to guide migrating snakes
into these tunnels. Mortality has been reduced by almost 75%. As a greater
understanding of snake migration patterns emerges, improvements will
be undertaken to increase the effectiveness of the system.
The red-sided garter snake can be found from the Northwest
Territories south to Oklahoma, east to Ontario and west to British
Columbia (Preston 1982). The red-sided garter snake occurs in the
southern part of Manitoba north to Flin Flon. It is absent from
the extreme southwestern grasslands except for Spruce Woods
Provincial Park. The preferred habitat of the red-sided garter
snake is near ponds in areas of moderate moisture (Preston 1982).
This habitat choice is likely due to the presence of food items
like frogs, leeches, tadpoles earthworms, and rodents (Preston
1982). In turn predatory mammals such as black bears, skunks and
raccoons eat the snakes. Birds, however, are their most serious
predators, many red-sided garters are killed each year by crows,
magpies, owls and hawks.
For more information on the red-sided garter snake, please see
the Conservation Data Centre Field Guide.
Sources:
Preston, W. 1982 The Amphibians and Reptiles of Manitoba.
Manitoba Museum of Man and Nature. 128 pp.
Fitch, H.S. 1965. An Ecological Study of the Garter Snake, Thamnophis
sirtalis. University of Kansas Publications, Museum of Natural
History, 15(10):493-564.
Gregory, P.T. 1977. "Life-history Parameters of the
Red-sided Garter Snake (Thamnophis sirtalis parietalis)in
an extreme environment in the Interlake Region of Manitoba."
National Museums of Canada Publications in Zoology 13. 44 pp.
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