on the nesting beach results in females being missed in intervening breeding seasons.
Breeding rates of male sea turtles have been poorly studied, and more information is needed. Males may breed at greater frequency than females; substantial proportions of males may breed annually (Hamann et al., 2003). Newer techniques, such as ultrasound, are useful and minimally invasive for evaluating the reproductive condition of adult sea turtles of both sexes. If the kidney is located first as a landmark in the male, the size and density of the testis and epididymis (parts of the male reproductive system) can be determined and the diameters of epididymal tubules measured for comparative studies (Blanvillain et al., 2008). Male breeding rates will inform our understanding of the proportion of males in a population required for successful reproduction and our understanding of possible depensation effects. (Depensation is described in the section “Density Dependence” later in this chapter.)
Recruitment of females into the breeding population and the proportion of first-time breeders in a nesting population are critical for assessing population trends. For example, if a nesting population is increasing in abundance, is the increase the result of increased recruitment of first-time breeders, increased survival of mature females, or both? In nesting populations subject to saturation tagging (tagging of every female) for a duration longer than the remigration interval with no loss of individual identification through tag loss and no immigration due to low fidelity, recruitment can be measured directly as the number of females that arrive with no tags (Richardson et al., 2006; Dutton et al., 2007). Few studies, however, meet those requirements. Another technique, laparoscopy, can be performed on female sea turtles at rookeries to determine the proportion of females that are first-time breeders or performed on foraging grounds to assess the proportion of female recruits that are preparing to breed in that year (Hamann et al., 2003). However, a method that is less invasive and more rapid is needed to distinguish recruits from females that have nested in previous seasons.
Fecundity is the reproductive output of an individual or a population. In sea turtles, fecundity is usually measured as the number of eggs deposited during a nesting season, which when combined with breeding rate (see above) yields an estimate of lifetime fecundity (average breeding rate multiplied by average reproductive lifespan). Within a nesting season, egg output of an individual is the product of the number of clutches deposited (clutch frequency) and the number of eggs in each clutch (clutch size). Egg size is usually not considered a measure of