Experimental analysis of an early life-history stage: avian predation selects for larger body size of hatchling turtles

One common life-history pattern involves an elevated rate and nonrandom dis tribution of neonatal mortality. However, the mechanisms causing this patte rn and the specific traits that confer a survival benefit are not always ev ident. We conducted a manipulative field experiment using red-eared slider turtles to test the hypothesis that diurnal avian predators are a primary c ause of size-specific neonatal mortality. Body size was a significant predi ctor of recapturing hatchlings alive and of finding hatchlings dead under n atural conditions, but was unimportant when diurnal predators were excluded from the field site. Overall recapture rates also more than doubled when p redators were excluded compared to natural conditions (72.4 vs. 34.9%). We conclude that birds are an important cause of size-specific mortality of re cently emerged hatchling turtles and that 'bigger is better' in this system , which has important implications for life-history evolution in organisms that experience size-specific neonatal mortality.