Strike-induced chemosensory searching in Old World vipers and New World pit vipers

It is known that striking rodent prey induces a sustained, high rate of tongue flicking in rattlesnakes. The present study shows this phenomenon (called strike-induced chemosensory searching, SICS) to occur in species of rattlesnakes not previously investigated and in two species ofAgkistrodon. SICS occurs in Old World vipers (Eristocophis, Vipera, Bitis), including species which normally hold their prey after striking. A hypothesis is offered which (1) accounts for the occurrence of SICS in these latter species and (2) suggests that SICS in some viperids may have arisen through paedomorphic evolution. More generally, it is concluded that SICS is probably a homologous trait in vipers and pit vipers and that the trait may have first appeared in elapid ancestors of the viperidae.