Most islanders have seen garter snakes in their yards or on a walk in the woods. These beneficial, often brightly striped snakes are specially adapted to our damp climate, bearing live young rather than laying eggs, and hibernating through the coldest months in underground cavities. Garters are fond of slugs and snails, so they are perfect companions for island gardeners.
Garter snakes can be more or less aquatic, and at least one of our islands’ native species, the Wandering Garter Snake (Thamnophis elegans vagrans), not only frequently hunts in shallow marine waters along our shorelines, but also swims out to small isolated islands in its search for prey. The Wandering Garter Snake is the only reptile that Kwiaht biodiversity inventory teams have encountered throughout the San Juan Islands National Monument, even on rocks as small as an eighth of an acre.
In addition to small fish and gastropods, garters eat amphibians such as frogs and salamanders. They tolerate the tetrodotoxin in the skin of Rough-Skinned Newts, making them a control on newt populations. Their aquatic skills also make them key predators of beetles, grasshoppers, and perhaps bird chicks on small islands.
Wandering Garters appear to be our largest island snakes, often attaining a length of more than 36 inches. Despite their size and carnivorous livelihood, they are quite shy, and will slip off silently into the underbrush or beneath rocks if disturbed. It’s a good idea to avoid handling garters – not only to spare these useful snakes from injury, but because a frightened garter may slime your hands with a persistent stinky goop, their only defense against predators such as owls and raccoons.
The Wandering Garter Snake is just one of at least three garter snake species that share the San Juan Islands with us. Unfortunately they are difficult to distinguish visually from each other, and from a half-dozen more garter snakes commonly found on mainland western Washington. Colors and stripes are not useful for identification. Colors vary even within a single litter from a common mother. In fact, the biologists at Kwiaht hope to get help collecting shed snake skins for DNA analysis so that the numbers of different garter snake species in the islands can be estimated more accurately.
Celebrate the native reptiles and amphibians of San Juan Island and find out how you can help learn more about them: join Russel Barsh of Kwiaht and Shona Aitken of Wolf Hollow Wildlife Rehabilitation Center at San Juan Island Library Oct. 30 for Sssslithery! an evening of family friendly island herpetology. Slide show and displays, refreshments. Come in costume (preferably a slithery one) and win a door prize! The festivities begin at 7 p.m. and admission is free.
For more information contact: Rainah Sandstrom, kwiaht@gmail.com
