AA << report snake species throughout the globe possess a mutation that protects them from a class of cardiotonic steroids known as bufadienolides, contained in the skin of some toads, even if the toads aren't part of the snakes' diet. >>
Feast without fear: Scientist says more snake species resist toxin. Nov. 22, 2016
http://m.phys.org/news/2016-11-feast-scientist-snake-species-resist.html
Shabnam Mohammadi, Zachariah Gompert, et al. Toxin-resistant isoforms of Na+/K+ -ATPase in snakes do not closely track dietary specialization on toads. Proc. of the Royal Soc. B: Biol. Sci. DOI: 10.1098/rspb.2016.2111. Publ. 16 Nov. 2016.
http://rspb.royalsocietypublishing.org/content/283/1842/20162111