Gape size and evolution of diet in snakes: feeding ecology of erycine boas

The Macrostomata accounts for more than 85% of extant snakes and is charact erized by increased mobility of the jaws and increased gape size. We used s tomach contents of museum specimens and specific literature records to desc ribe the food habits of a basal clade of macrostomatan snakes - the erycine boas (Erycinae) - with an emphasis on the North American Charina bottae. M ammals, lizards, birds, and squamate eggs composed 66%, 17%, 7%, and 5%, re spectively, of the prey of C. bottae. Smaller C. bottae fed on squamate egg s and lizards, whereas larger snakes added mammals and birds to their diet, and ceased to take squamate eggs. Ten of 12 snakes with multiple prey had eaten nestling birds or mammals, and snakes that ate multiple prey were not significantly larger than those that had single prey. Charina trivirgata a nd C. reinhardtii also prey on mammals, whereas species of Eryx feed mainly on mammalian prey, but also eat lizards and occasionally birds. Evolutiona rily more basal groups of snakes primarily feed on elongate prey, which sug gests that innovations of the feeding apparatus of macrostomatans allowed t hese snakes to eat heavier and bulkier prey, particularly mammals. Erycines appeared and diversified at approximately the same geological time as rode nts, suggesting that rodents perhaps constituted an abundant prey resource that favoured the diversification of early macrostomatans.