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Niche partitioning within a population of seasnakes is constrained by ambient thermal homogeneity and small prey size

Citation

Shine, Richard; Goiran, Claire; Brown, Gregory (2019), Niche partitioning within a population of seasnakes is constrained by ambient thermal homogeneity and small prey size, Dryad, Dataset, https://doi.org/10.5061/dryad.xpnvx0kbm

Abstract

In many populations of terrestrial snakes, an individual’s phenotype (e.g. body size, sex, colour) affects its habitat use. One cause for that link is gape-limitation, which can result in larger snakes eating prey that are found in different habitats. A second factor involves thermoregulatory opportunities, whereby individuals select habitats based upon thermal conditions. These ideas predict minimal intraspecific variation in habitat use in a species that eats small prey and lives in a thermally uniform habitat – such as the seasnake Emydocephalus annulatus, that feeds on tiny fish eggs and lives in inshore coral-reefs. To test that prediction, we gathered data on water depths and substrate attributes for 1475 sightings of 128 free-ranging E. annulatus in a bay near Noumea, New Caledonia. Habitat selection varied among individuals, but with a preference for coral-dominated substrates. A snake’s body size and reproductive state affected its detectability in deep water, but overall habitat use was not linked to snake body size, colour morph, sex, or pregnancy. A lack of ontogenetic shifts in habitat use allows extreme philopatry in E. annulatus, thereby reducing gene flow among populations and potentially, delaying recolonization after local extirpation events.