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 distribution of neonatal mortality. However, the mechanisms causing this pattern and the specific traits that confer a survival benefit are not always evident. We conducted a manipulative field experiment using red-eared slider turtles to test the hypothesis that diurnal avian predators are a primary cause of size-specific neonatal mortality. Body size was a significant predictor of recapturing hatchlings alive and of finding hatchlings dead under natural conditions, but was unimportant when diurnal predators were excluded from the field site. Overall recapture rates also more than doubled when predators were excluded compared to natural conditions (72.4 vs. 34.9%). We conclude that birds are an important cause of size-specific mortality of recently 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.