By Russel Barsh
Director, KWIAHT
An olive-green snake slips into the water and disappears beneath the kelp…
Viewers of David Attenborough’s Planet Earth III, Episode 1, have been handled to scenes of a snake looking small fish in a shallow rocky reef at Saturna Island. In actuality, a lot of the analysis on this uncommon snake conduct was carried out right here within the San Juan Islands by Kwiaht herpetologist Christian Oldham in 2022, with funding offered by the BBC.
The “wandering” garter snake (Thamnophis elegans vagans) just isn’t solely the biggest native snake of the San Juan and Gulf Islands, able to rising to greater than three toes; it routinely swims ponds and lakes, feeding on fish, frogs, and maybe an occasional duckling. Sporadic reviews of those snakes coming into salt water culminated a couple of years in the past in movies of a garter snake fishing in tide swimming pools at Saturna Island.
BBC producers have been intrigued. They contacted Kwiaht to be taught whether or not this type of conduct is typical of garter snakes within the islands. We didn’t have a solution. What adopted was a season of observing seashores, setting out infrared-triggered cameras, and conducting experiments in a specially-designed saltwater tank the place snakes have been provided the chance to dive after tide pool fish resembling sculpins and gunnels.
The shore observations have been irritating; twice, a wandering garter snake was seen heading up a seaside after presumably looking alongside the tideline, or beneath the tide. Tank experiments have been much more informative: randomly collected island snakes that dove in with out hesitation, catching and consuming the fish provided. In different phrases, fishing in salt water is “wired into” the island inhabitants of this species. Given the chance, they are going to hunt in saltwater as readily as freshwater.
What does this all imply for our island ecosystem?
The proven fact that our largest native snake could make its residing fishing is a major benefit within the islands, which have a really excessive ratio of shoreline to land space. Our most profitable omnivorous wild mammals are additionally not less than partly reliant on marine assets: raccoons, otters, and minks. At least two of our bat species have tailored to looking bugs over salt water, furthermore. Even our diminutive island deer, whereas they rely almost solely on terrestrial crops, have been seen swimming from island to island in seek for greener pastures (and mates). In a way forward for rising sea ranges and stormier winters, wildlife that swim and make the most of nearshore assets will get pleasure from a definite benefit.
Marine-adapted wildlife are particularly related to the hundred or so small, uninhabited islands which are scattered all through our archipelago. They usually are not solely the area of seabirds. Our crew has discovered garter snakes roaming a lot of them, along with beetles, slugs and snails for these seafaring reptiles to eat when they don’t seem to be munching fish. On small islands, garter snakes can play a comparatively higher ecological position than they do on the bigger islands the place they have to share assets with extra landlocked predators.
