Drought Tolerance of Pelagic Sea Snakes in Costa Rica
Résumé
We tested the hypotheses that (1) pelagic sea snakes (Pelamis platurus) dehydrate during the dry season when precipitation is absent (Dec- May) off the Guanacaste coast of Costa Rica, and (2) these snakes utilize coastal rivers as sources of fresh water. We looked for sea snakes at coastal sites near Playas del Coco, counted the numbers of snakes, measured water salinity, and determined whether captured snakes would drink fresh water during a 20-h test period immediately following capture. Most snakes were observed on slicks or drift lines and were found in roughly equal abundance during early February and during mid-April, 2010. Contrary to expectation, snakes were less abundant near each of two rivers than at sites farther out from the coast. Water salinity varied from 32-34 PPT during February and from 34- 35 PPT during April. Three of 25 snakes (12%) returned to the laboratory in February drank fresh water, and 5 of 49 snakes (10.2%) drank freshwater when captured in April. February snakes drank 3.7 ± 2.6 (SD) % body mass, whereas April snakes drank 7.1 ± 4.4 % body mass. Indices of body condition suggest these snakes were only moderately dehydrated. We conclude that some individuals dehydrate to unknown extent during the dry season, but the majority of snakes in the population survive the dry season without severe dehydration while at sea without access to estuarine sources of fresh water.