[Cazador]

That's right, Stefan. Even the newborns would be immune.

Sabine,
I've read papers that say there is a correlation between the amount of red on garter snakes and their ability to eat toxic species. I know that the California red-sided garter has a degree of immunity to toxic newts and salamanders in its diet, but I don't know if it has the same mechanism. I suspect it does, though. I wouldn't be surprised if this mutation is more widespread than we know among other species and subspecies.

Matt,
If the mutation happened in a germ cell (sperm or egg), then the immunity would be heritable. This obviously happened in this case, since the phenomenon is so widespread. Since the mutation exists in germ cells, then you could interbreed with an eastern, giving the eastern's offspring immunity. It may not occur in one generation, though. If the mutation is a dominant trait, then all of the offspring would have immunity. If it's a recessive trait, then none of the first generation of offspring would be immune. If the offspring mated among themselves, then statistically speaking, only 1 in 4 would would be immune. This is probably a dominant trait, though, so all of the offspring would be immune. Any red spots that aren't immune would die if they ate these toxic newts, so I suspect that practically all have the mutation (and immunity).

Rick