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Energy Resource Allocation and Use in Reproducing Olive Ridley Sea Turtles
Abstract
Identifying where and when endangered sea turtles obtain energy for egg production is critical for designing effective management plans for species’ recovery. Whereas most sea turtles exhibit a capital breeding strategy, storing energy as lipid prior to reproduction and utilizing it while fasting over the nesting period, characteristics of olive ridley sea turtles (Lepidochelys olivacea), including small body size, annual mass nesting, and highly nomadic, pelagic migrations suggest they may instead actively feed at nesting areas, termed an income breeding strategy. To evaluate this possibility, anatomical and physiological measures were used to assess potential lipid intake and utilization by reproductively active female olive ridleys. Olive ridleys were sampled in Costa Rica during May-September of 2016, 2017, and 2018 and classified according to reproductive behavior (mating or nesting), ovarian state (no observable atretic ovarian follicles “early” or presence of atretic follicles “late”), and recapture state (initial sample or resample at subsequent nesting). Body condition scores (BCS) declined between mating and nesting, but did not differ by ovarian or recapture state. Likewise, a newly developed ultrasound technique to measure subcutaneous fat thickness (SQFT) did not differ by behavior or ovarian state and did not correlate with BCS. Blood vitellogenin concentrations remained elevated throughout the reproductive season in all years, indicating continued lipid demand until late in the reproductive season. A physiological measure of stored lipid mobilization, circulating beta-hydroxybutyrate (BHB), the primary ketone body produced by the liver during fasting, showed no significant change by reproductive behavior or ovarian state; whereas ghrelin, a fasting-sensitive hormone, declined. Overall, these results provide no evidence that olive ridleys are fasting during nesting. However, in a subset of recaptured females, BHB and SQFT both remained low and unchanging in 2017, corresponding to visible presence of intestinal content via ultrasound, supporting feeding behavior. In 2016, SQFT and BHB were elevated early in the season and declined. These results suggest that olive ridleys may employ a capital strategy during years of low resource availability, as 50% fewer animals had visible intestinal contents in 2016, a strong El Niño Southern Oscillation year. These results suggest that olive ridleys are mixed strategy breeders, which may enable high reproductive resilience when resources are limited and contribute to their status as the most abundant sea turtle species.
Subject
Lepidochelys olivaceaolive ridley sea turtle
capital breeding
income breeding
mixed breeding
Citation
Myre, Brianna Lynn (2022). Energy Resource Allocation and Use in Reproducing Olive Ridley Sea Turtles. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198010.