Abstract
Diel activity patterns are an important aspect of wildlife ecology and evolution and provide valuable information for conservation and monitoring, yet for many species, activity patterns remain unstudied and may be presumed to mirror related taxa. Here, we describe the distinct diel patterns of an endemic population of venomous sea snakes Hydrophis platurus xanthos inhabiting a narrow range (circa 320 km2) in Golfo Dulce, Costa Rica. To investigate, we conducted a systematic visual survey over five 24‐h cycles and evaluated 339 h of previously obtained sighting data from different studies spanning a decade. While sporadic diurnal surfacing does occur, mostly for respiration, our observations revealed marked crepuscular peaks with regular surfacing through the night. We also report on observed surface behaviors that were also found to vary in frequency at different phases of the photoperiodic cycle. In particular, we show feeding as more common at night. Hydrophis platurus xanthos has developed a circadian rhythm that differs noticeably from its taxonomic parent (H. p. platurus is reported as diurnal across its Indo‐Pacific range), and no congeners have been categorized as crepuscular. Our work thus contributes to the ecological knowledge of this evolutionarily distinct marine elapid and offers insights into the potential role of environmental conditions in shaping animal activity.
Highlights
Animal activity patterns are an important aspect of ecology and evolutionary biology, yet they are an understudied facet of behavioral ecology due to the challenges of recording and quantifying the behaviors of free-ranging populations over time-specific periods (Bridges & Noss, 2011)
Hydrophis platurus xanthos is endemic to the inner-basin waters of Golfo Dulce, Costa Rica, an area with higher sea surface temperatures (SST) and lower salinity than those found in the neighboring Eastern Tropical Pacific Ocean (Rasmussen et al, 2011; Rincón-Alejos & Ballestero- Sakson, 2015; Wellington & Dunbar, 1995)
Because we considered all observed behaviors and sometimes more than one behavior was observed in the same snake, our model results could have been influenced by pseudoreplication, and because we recorded a single behavior for most snakes, using snake ID as a random factor resulted in convergence issues
Summary
Animal activity patterns are an important aspect of ecology and evolutionary biology, yet they are an understudied facet of behavioral ecology due to the challenges of recording and quantifying the behaviors of free-ranging populations over time-specific periods (Bridges & Noss, 2011). Activity is usually meant to denote movement (Aschoff, 1954), observed as periods of foraging, traveling, or reproductive behaviors juxtaposed to periods of stillness (resting or sleeping) Certain fauna, such as air-breathing marine snakes that must regularly surface to ventilate, may not present such defined periods. Hydrophis platurus xanthos is endemic to the inner-basin waters of Golfo Dulce, Costa Rica, an area with higher sea surface temperatures (SST) and lower salinity than those found in the neighboring Eastern Tropical Pacific Ocean (Rasmussen et al, 2011; Rincón-Alejos & Ballestero- Sakson, 2015; Wellington & Dunbar, 1995) This allopatric population has transitioned from a black-backed, yellow-bellied phenotype to monochromatic xanthic (yellow) coloration and smaller body size (Bessesen & Galbreath, 2017), presumably to avoid overheating under solar exposure (Bessesen, 2012; Solórzano, 2011). Our results help fill several knowledge gaps, adding to the literature on behavioral ecology in sea snakes and the adaptive evolution of geographically isolated organisms, while demonstrating the potential for dynamic diel patterns to be recorded on a population scale
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