Marine Biology (1995) 123;197-205
Body temperature independence of solar radiation in free-ranging loggerhead turtles, Caretta caretta, during internesting periods
Katsufumi Sato, Wataru Sakamoto, Yoshimasa Matsuzawa, Hideji Tanaka, Shingo Minamikawa, Yasuhiko Naito
Body temperatures, ambient water temperatures, light intensities and vertical positions (depth) of eight loggerhead turtles, Caretta caretta, were monitored by small recorders during internesting periods from 1991 through 1993 off Wakayama Prefecture, Japan. Body temperature of eight loggerhead turtles were higher than ambient water temperature throughout their internesting periods. Light intensities were compared with body temperatures and no evidence was obtained to suggest that the raised body temperature were caused by the direct influence of solar radiation. Body temperatures were kept higher than water temperatures in cloudy weather or even at night. Mean thermal differences between body and water temperatures significantly different among individuals, and larger turtles had a greater mean thermal difference. Elevation in body temperatures of adult loggerhead turtles can reasonably be assumed to result from the accumuration of metabolically produced heat. Surfacing times (spent at depths shallower than 2 m) of seven turtles were only 10.3 to 38.9% of their internesting periods, with the exception of one turtle who spent 66.3% of her time at the surface. Loggerhead turtle did not seem to bask positively at the sea surface to absorb radiative heat.
TU95-1
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