Species belonging to three nominal genera of Asian natricine snakes possess defensive glands in the dorsal skin,either in the neck(nuchal glands)or along the entire trunk(nucho-dorsal glands).In the best-studied species,Rhabdophis tigrinus,the nuchal gland has been shown experimentally to deliver bufadienolide toxins(BDs)sequestered from toads(Bufo)consumed as prey.