Abstract/Summary

Hydrophis platurus xanthosis a marine reptile endemic to the inner basin ofGolfo Dulce, Costa Rica, and one of only two sea snake taxa found in the NewWorld. In this study we assessed several marine conditions that describe itshabitat, and we define its geographical distribution range. We used 423 occur-rence records ofH. p. xanthoscollected during multiple studies to model habi-tat suitability in Maxent considering water depth and 12 interpolatedhydrographic variables: Beaufort wind force, sea surface temperature, andaverages of temperature, salinity, dissolved oxygen, turbidity, and pH at 0.5and 10 m based on probe readings collected in 2020 and 2021 at 68 samplinglocations. We used area under the curve (AUC) to evaluate our Maxent modelsand the cloglog minimum training presence threshold to render our suitablehabitat maps. The most influential environmental predictor was depth, butoccurrences were also affected by hydrographic conditions. Indeed, a modelexcluding depth consistently identified only areas in and around the innerbasin area as suitable, suggesting the sea snakes are not only restricted bydepth but likely have adapted to water conditions that differ from those fartherto the south and outside the gulf in the broader Pacific Ocean. Anthropogenicand climate-induced changes may already be impacting the marine environ-ment of this single, isolated population. Our study offers the first quantitativeevaluation of habitat suitability forH. p. xanthosand we estimate its extent ofoccurrence (282 km2) and current area of occupancy (260 km2) to inform con-servation assessments and guide protection measures.