Does foraging mode influence life history traits? A comparative study of growth, maturation and survival of two species of sympatric snakes from south-eastern Australia

Theory predicts that compared with active searchers, ambush foragers should have lower rates of energy intake, slower growth, and higher survival rates. We tested these predictions with data on two species of sympatric, saurophagous, small-bodied, viviparous elapid snakes: the broad-headed snake, Hoplocephalus bungaroides, and the small-eyed snake, Rhinoplocephalus nigrescens. Demographic parameters and growth curves for both species were estimated from a long-term (9 years) mark-recapture study in Morton National Park, south-eastern Australia. The ambush predator (H. bungaroides) displayed slower juvenile growth and later maturation (5 years for males, 6 years for females) than did the active forager (R. nigrescens, 3 years). Litter sizes were similar in both species, but reproductive frequency was higher in R. nigrescens (90-100%) than in H. bungaroides (50%). Juvenile survival was lower in the active searcher (31%) than in the ambush forager (55%), but adult survivorship was similar (74% vs 82%). Our results support the hypothesis that ambush foragers display 'slow' life history traits, but additional phylogenetically independent comparisons are needed to evaluate the generality of this pattern.