Internesting intervals for loggerhead turtles, Caretta caretta, and green turtles, Chelonia mydas, are affected by temperature

Abstract

To investigate the influence of temperature on the length of internesting periods in loggerhead turtles (Caretta caretta) and green turtles (Chelonia mydas), body temperature and water temperature and depth for free-ranging turtles were monitored during internesting periods using micro data loggers. Body mass and clutch size were also measured. The experiments were conducted at nesting beaches in the Japanese archipelago from 1989 through 1996. Internesting interval was significantly negatively correlated with mean body temperature and mean water temperature. Internesting intervals for some turtles exceeded 21 d when they experienced low water temperatures. Arrhenius' equation was used to describe the quantitative relationships, and Q10 values of 3.1 for water temperature and 3.4 for body temperature were calculated. There was no significant relationship between either clutch size or body mass and internesting interval. Body temperatures were kept higher than water temperatures throughout internesting periods, and larger turtles showed a higher mean thermal difference between body temperature and water temperature. The internesting interval could be considered an egg-maturation period for the next oviposition. The rate of pre-ovipositional development of eggs seemed to be accelerated by high body temperature and decelerated by low body temperature.