BARBIERI, M/M*; MCLELLAN, W/A; WELLS, R/S; HOFMANN, S; PABST, D/A; UNC Wilmington; UNC Wilmington; Mote Marine Lab; Mote Marine Lab; UNC Wilmington: Seasonal patterns in dorsal fin surface temperatures of free-ranging bottlenose dolphins (Tursiops truncatus) in Sarasota, FL

The dolphin dorsal fin is a thermoregulatory control surface containing vascular structures that function in both heat conservation and dissipation. The goal of this study was to measure the response of this thermal window to seasonal changes in environmental temperature in wild, free-ranging bottlenose dolphins (Tursiops truncatus) in Sarasota, FL. These resident dolphins can experience yearly water temperatures ranging from 11 to 33�C. The temperature differential between the skin surface and ambient environment (ΔT) strongly influences heat loss. We hypothesized that dolphins would need to conserve body heat in winter and would exhibit a smaller ΔT during this season. We used non-invasive, infrared thermography (FLIR Agema 570, ThermaCam Researcher 2001) to measure dorsal fin surface temperatures of dolphins (n=551 images) encountered during synoptic surveys in the summer, fall, and winter from 2002-2004. Water temperatures were independently measured during each sighting (Aquacal� ClineFinder). There was a positive, linear relationship between dorsal fin surface temperature and water temperature (r²=0.978; p<0.001), as mean ΔT across all seasons (0.9�C) was similar. Thus, a much larger temperature gradient between the dolphin core and the dorsal fin surface existed in winter than in summer. Dorsal fin surface temperatures appear to be modulated in response to environmental temperature to maintain a steady ΔT at the dorsal fin skin surface across seasons. In winter, increases in insulation, both integumentary (i.e. blubber) and vascular (via reduced perfusion and utilization of heat exchangers) must account for the protection of core temperature and stability of ΔT.