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Satellite tracking has revolutionized our understanding of the behavior and ecology of sea turtles. However, most satellite tracking of sea turtles has been performed on breeding females, leaving knowledge gaps with regard to males. To inform future studies, we examined the peer-reviewed literature to summarize the contribution that satellite tracking has made to the spatial ecology of male turtles and describe how the published research varies across time, species, life stages, seasonal cycle phases, regions, and research topics. We systematically reviewed 61 publications reporting tracking of male sea turtles across 6 species. Loggerheads emerged as the most studied species, featuring in 49% of the publications, with green turtles and loggerheads having the highest number of tracked males. The North Atlantic was the most represented region (39% of publications), followed by the Mediterranean (29%). Most tracking of males has been undertaken at foraging areas (77%), often providing information on home range residency. This is followed by migration publications (44%), which have revealed differences among populations and between sexes, with the breeding period being the least studied. We highlight differences in the spatial ecology of males and females (e.g. residency in breeding areas and migration distance) and identified unanswered research questions about male sea turtles. To overcome the lack of knowledge about this important demographic group, efforts should be undertaken to increase the sample size and geographic coverage of tracked males, with special focus on flatback and Kemp’s ridleys, as well as studies in the Indian and Pacific Oceans.
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Potential drivers and implications of a balanced breeding sex ratio in a small population of an imperiled species with environmental sex determination
Abstract Small populations of imperiled species are susceptible to the negative consequences of skewed sex‐ratios. In imperiled species with environmental sex determination such as sea turtles, examining sex ratios across a range of environments and population abundance levels can provide insight into factors that influence population resilience, which can then be the foci of management plans for these species. Breeding sex ratios (the ratio of actively breeding males to females during a reproductive season; BSRs) extrapolated from genetic parentage analyses are a common approach for enumerating sex ratios in sea turtles. Such analyses also allow for the characterization of multiple paternity within sea turtle clutches, which should reflect BSRs and breeding behaviors. We characterized the first BSR for a breeding assemblage of loggerhead sea turtles (Caretta caretta) belonging to the temperate, low‐abundance Northern Gulf of Mexico Recovery Unit using genotypes of 16 microsatellite loci from nesting females and hatchlings. Unlike prior studies at both more‐tropical and more‐temperate, and higher‐abundance, Recovery Units in this region, we found a balanced BSR of 1.3:1 males:female and a low incidence (~17%) of multiple paternity. This suggests that there are relatively few males breeding at this assemblage and within this Recovery Unit. Beaches in this region are expected to produce substantial numbers of male hatchlings based on sand temperature data. The relative dearth of mature males may then be due to hydrologic disturbances that disproportionately affect the fitness and survival of male hatchlings, or due to demographic stochasticity. More work is needed to study the factors that might influence male hatchling production and fitness in this region, particularly as climate change is predicted to lead to feminization in global sea turtle populations. Our work demonstrates the broad utility of characterizing BSRs and other sex ratios across a range of populations in imperiled, environmentally sensitive species.
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- Award ID(s):
- 1904818
- PAR ID:
- 10576824
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 14
- Issue:
- 9
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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