Pelagic Sea Snakes Drink Fresh Water at Beginning of Wet Season

Abstract

The Yellow‐bellied sea snake (Hydrophis platurus) is the only pelagic species of marine snake and ranges from southern Africa across the Indo‐Pacific to the Pacific coast of Central America. It is subject to long‐range movements by drifting with gyres and currents, and it is the only species of sea snake to have reached the Americas. Like other sea snakes investigated recently, this species is dependent on fresh water (FW) and dehydrates at sea during periods of drought. Because of its pelagic marine habitat, the only source of FW for this snake is rainfall that forms a freshwater or dilute brackish‐water lens during intense precipitation over the ocean. In the coastal region of Guanacaste, Costa Rica, there is a 6‐mo dry season without significant rainfall usually ending in May. During a research trip to Costa Rica from 5 to 14 May 2017, we captured H. platurus daily during the morning and returned them immediately to the laboratory where they were air‐dried, weighed, and placed individually in FW. Snakes were held in FW for approximately 20 h, following which they were air‐dried on a towel and reweighed. Drinking of FW was observed immediately when some snakes were placed in FW; others were determined to have ingested water by changes in mass that occurred overnight (5 to 27 % body mass; mean = 14.2 ± 0.87 s.e.m.). When we arrived in Costa Rica, there had not been significant rainfall at the location where snakes were studied; the weather was hot and dry, and there was no precipitation over the ocean. A large proportion of snakes that were captured during the first two days drank FW. Between the second and third day there was heavy rainfall during the afternoon, and we observed that rain fell in large amounts over the Golfo de Papagayo where we collected the snakes. During the next several days, heavy rainfall occurred during the afternoon or evening, and precipitation again fell over the ocean. The percentage of snakes drinking after capture decreased with time, falling from ~ 80% before the rains began to 13% on the seventh day. Our data clearly indicate that fewer and fewer snakes were in negative water balance as the wet season began in context of precipitation we observed over the ocean. Thus, it is appropriate to conclude that thirsty snakes having accumulated a water deficit during the previous dry season were drinking from FW‐brackish oceanic lenses when precipitation began to fall over the Golfo de Papagayo. We were extremely fortunate to be able to quantify drinking behaviors of sea snakes precisely at the transition from dry to wet season when rainfall first impacted the ocean at our location. These data reinforce the importance of fresh water for pelagic sea snakes, which dehydrate in the ocean and are thus susceptible to changing patterns of precipitation that might result from climatic changes related to global warming.Support or Funding InformationNational Science Foundation grant IOS‐0926802 to HBLThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.