Alaska is a big state,I’ve never been there and would like to go there someday but,unless you’ve personally explored it in it’s entirety,I’ll side with the experts.Pretty resilient critters them garter snakes.
“The common garter snake lives in far southeast Alaska. There are no snakes in most of the state, which gives rise to the common perception that there are no snakes at all in Alaska. This is an overstatement, however.”
“Garter snakes have been occasionally reported along the Alaska Panhandle, but their presence in the state has not been definitively confirmed. If found, they should be left alone, because reptiles and amphibians in general may not be collected for commercial purposes, nor have open seasons or legal takes been defined for them.”