This is why you train it to be an ordinary search/scent dog and train the same as you would for tracking in the field. Don't train it how to recognize and find snakes, but rather train it to pick up the scent you give it (a whiff of newspaper or aspen from under your snake's favorite resting spot) and to follow that scent to it's conclusion.
This way, there is still work outside of the highly specified niche of snake finding. lol