Feeding Strategies in Marine Snakes: An Analysis of Evolutionary, Morphological, Behavioral and Ecological Relationships

Abstract

Analysis of 1,063 stomach contents from 39 species of sea snakes indicates that about one-third of the shallow, warm, marine, Indo-Australian fish families are preyed upon by sea snakes. Families of eels and gobies are taken by the greatest numbers of snake species. Most species of sea snakes feed on fish families whose members are relatively sedentary, dwelling along the bottom, within burrows or reef crevices. With one exception, a fish egg-eating specialization found uniquely in the Aipysurus-Emydocephalus lineage, the dietary habits of sea snakes cannot be categorized according to the snakes' three phylogenetic lineages. Eels, mullet-like, rabbitfish-like and goby-like fish forms are taken by all three lineages. Two or three snake species are generalists, and numerous ones specialize on eels, goby-like fish or catfish. There are differences among sea snake species in the relationship between snake neck girth and the maximum diameter of the prey; in the relationships of both snake gape measurements and fang length, to the type of prey taken; and in the relationship of snake shape and body proportions to the prey selected. Several modes of feeding have been observed among sea snakes: feeding in nooks and crannies in the bottom or in reefs, cruising near the bottom, and feeding in drift lines. Analysis of percent digestion of stomach contents and projections backward to the times of prey capture provides evidence for feeding periodicity. The greatest amount of diet overlap is for two species of sea snakes which do not both occur at the same locality. Where species do co-occur, diet overlap index values are lower. The numbers of species present as well as their relative abundances vary among localities as does the relative importance of generalists, eel-eaters, egg-eaters and other specialized feeders.