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

Abstract

The goal of this study was to assess the consequences of single versus multiple paternity by identifying paternity of clutches per female to identify whether 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.

Conservation Genetics of the Loggerhead Sea Turtle, Caretta caretta, from the Central Mediterranean: An Insight into the Species’ Reproductive Behaviour in Maltese Waters

“…Such delayed renesting events and the choice of a totally different nesting area may be the result of human presence and disturbance, which affect the females’ decision when opting for a nesting beach [ 66 ]. In this instance, we cannot exclude the possibility that Mother 3 laid other unrecorded nests in the interval between CMA and CRA, given that female C. caretta can lay more than two clutches in a season [ 67 ]. We were unable to detect cases of a female returning to nest in a different nesting season twice, up to now, since female C. caretta have a nesting interval of two to three years and the nests we analysed covered a shorter period of time [ 2 , 24 ].…”

“…Unlike some other species of turtles [ 83 , 84 ], C. caretta does not store sperm across breeding seasons [ 85 ]. Therefore the occurrence of multiple paternity is the result of multiple mating encounters and sperm storage for each breeding season, as loggerhead sea turtles rarely mate between nesting events within the season [ 67 ]. This is consistent with the observations noted in this study where the instances of renesting were represented by the same parentage.…”

Within-season shifts in multiple paternity patterns in mass-nesting olive ridley sea turtles

“…Another mechanism that could promote paternal contribution bias is sperm competition (Adams et al 2005). Sea turtles have the ability to store viable sperm obtained during multiple matings at the beginning of the reproductive season in their oviducts, creating the opportunity for sperm competition between multiple males (Gist & Jones 1989, Adams et al 2005, Phillips et al 2014, Lasala et al 2020. Low male contribution to a clutch could be the result of less competitive sperm or residual sperm stored from previous nesting season (Stewart & Dutton, 2011).…”

Forty years of monitoring increasing sea turtle relative abundance in the Gulf of Mexico

“…Much of the research on these and other species of marine turtles occurs on the East coast of Florida, where nesting density is high 52 – 54 . Few studies have focused on Florida’s Gulf of Mexico coastline 28 , 55 , 56 , despite the growing nesting populations in this region. Programs that have monitored marine turtle nesting over time are invaluable to identifying trends of how populations have changed through time 27 , 57 , 58 .…”