Female loggerhead sea turtles (Caretta caretta L.) rarely remate during nesting season

The goal of this study was to assess the consequences of single versus multiple paternity by identifying paternity of clutches per female to identify if there were detectable costs or benefits. Multiple mating can occur when the benefits of mating outweigh the costs, but if costs and benefits are equal, no pattern is expected. Previous research on loggerhead sea turtle (Caretta caretta) populations found male-biased breeding sex ratios and multiple mating by many females nesting in southwestern Florida. A sample of nesting loggerhead females who laid more than one nest over the course of the season and a subset of their hatchlings were examined from 36 clutches in 2016 on Sanibel Island, Florida. Males that fathered hatchlings in the first clutch sampled were identified in subsequent clutches. Interestingly, 75% of the females analyzed had mated singly. No male was represented in more than one female’s clutches. The results suggest that females likely mate at the beginning of the season and use stored sperm for multiple clutches. Evidence for mating between laying events was limited. There was no consistent pattern across the subsequent multiple paternity clutches, suggesting benefits to loggerhead females likely equal their costs and subsequent mating is likely determined by female preference.

本研究旨在通过鉴定每只雌性个体的窝卵父权，评估单次交配与多次交配的繁殖后果，以探明是否存在可检测的繁殖成本或收益。当交配收益高于成本时，雌性个体可能发生多次交配；若成本与收益相当，则不会出现偏向性的交配模式。此前针对蠵龟（Caretta caretta）种群的研究发现，其繁殖性比偏向雄性，且佛罗里达西南部的多数筑巢雌性存在多次交配行为。2016年，研究人员于佛罗里达州圣贝尔岛采集了36窝卵的样本，对该繁殖季内产卵不止一次的筑巢雌性蠵龟及其部分幼龟进行了检测分析。经鉴定，首次采样窝卵的父本雄性同样出现在了后续窝卵中。值得注意的是，经分析的雌性个体中有75%仅发生过单次交配，且未出现同一只雄性参与多只雌性窝卵繁殖的情况。研究结果表明，雌性蠵龟大概率在繁殖季初期完成交配，并通过储存精子完成多巢产卵。有关产卵事件间再次交配的证据十分有限。后续的多父权窝卵未呈现一致的模式，这提示雌性蠵龟的交配收益与成本大致相当，后续交配行为大概率由雌性偏好决定。