March’s
Species of the Month is actually a genus containing species. To celebrate Saint
Patrick’s Day, Nature Minute will take a broad look at the many different
garter snakes, which likely did not immigrate to America after being driven out
of Ireland. We’ll also explore the myth of Patrick’s divine snake charming. Information
and picture this month come from University of Michigan’s Animal Diversity Web
and Gartersnake.info. Our history lesson on Saint Patrick comes from National
Geographic.
Scientific
name: Thamnophis species
Kingdom:
Animalia (animals)
Class:
Reptilia (reptiles)
Order:
Squamata (lizards and snakes)
Range: Subarctic
Alaska and Canada to Central America
Habitat:
Varied. They can be found in forest, grassland, desert, and marshy areas. Commonly
found near water.
Lifespan: 2-3
years on average, 6-10 years in captivity
Diet: Varied.
May include amphibians, small rodents, small birds, small fish, insects, worms,
snails, and slugs.
Predators:
Fish, bullfrogs, snapping turtles, larger snakes, raccoons, great blue herons,
hawks and falcons, foxes, skunks, weasels, squirrels, owls, house cats, coyotes,
and crows.
Conservation
Status: Dependent on species. Butler’s garter snake is listed as threatened in
Canada and Wisconsin and listed as endangered in Indiana. Narrow-headed, northern
Mexican, and giant garter snakes are threatened throughout their ranges and San
Francisco garter snake is endangered. Eastern ribbon snake is threatened or
endangered in the US and Canada. The two-striped garter snake is protected in
California but not yet listed as threatened or endangered. The checkered garter
snake is listed as threatened in Kansas.
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| One of three near-identical species of garter snake in the Northwest |
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| One of three near-identical species of garter snake in the Northwest |
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| Mountain garter snake (from California Herps) |
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| Red spotted garter snake (from California Herps) |
Other
Information: There are 35 species of garter snakes and many have numerous
subspecies. On the whole, garter snakes are very numerous, in spite of the
above listings. Like all other snakes, garter snakes swallow their prey whole.
They do not squeeze their prey (non-constricting). Most garter snakes are
semi-aquatic and will likely be found in or near water. They are cold-blooded
and require less food energy to regulate their body temperatures than mammals,
birds, and other warm-blooded animals. However, that requires them to bask in
the sun or on hot rocks to keep warm. This is why most snakes you encounter are
just sitting idly. Here in Washington, there are three species of garter snake:
The western terrestrial, northwestern, and common. All look very similar and
come in a variety of colors. The only way to tell them apart is by counting
scales.
The legend
of Saint Patrick driving the snakes from Ireland stems from the absence of
snakes on the Emerald Isle and ties in nicely with the Christian image of the
serpent as an agent of evil. The myth of driving snakes from Ireland is likely
a metaphor for Patrick’s Christianizing the people, driving paganism out of
Ireland. Snakes were driven, or rather kept from Ireland by the last Ice Age.
It was too cold for snakes to live there and by the time it became warm enough
the sea level rose to the point that they could not slither there from England.
UM Animal
Diversity Web: http://animaldiversity.org/
Gartersnakes.info:
http://www.gartersnake.info/
National
Geographic: http://news.nationalgeographic.com/news/2014/03/140315-saint-patricks-day-2014-snakes-ireland-nation/
California Herps: http://www.californiaherps.com/index.html
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