Long-Term Monitoring of Swimming and Feeding Behaviors Related to Reproductive Cycles in Captive Loggerhead Turtles, Caretta caretta

Reproductive processes, including spermatogenesis and vitellogenesis, have been closely associated with the migratory and behavioral patterns of sea turtles. However, whether physiological changes associated with reproduction influence behavioral adaptations, particularly swimming and feeding patterns, remains unclear. Thus, this study aimed to examine the relationship between reproductive cycles (spermatogenic and vitellogenic) and behavioral patterns (swimming and feeding) in captive loggerhead turtles, Caretta caretta. Experiments were conducted from January 2011 to December 2012 at the Okinawa Churaumi Aquarium and involved one male and two female loggerhead turtles. Monthly measurements included serum testosterone levels in the male and triglyceride and total protein concentrations in the females. Behavioral observations of swimming and feeding were recorded to calculate activity ratios. Distinct seasonal variations were observed in the male and female turtles. In the male, testosterone levels and swimming activity increased from December, peaked during the mating season (March to April), and declined thereafter. Feeding activity decreased during the peak reproductive phase (February to April) and recovered after mating in May. In the females, triglyceride and total protein levels, along with swimming activity, increased during vitellogenesis (October to February) and peaked during nesting (March to April), whereas feeding behavior declined during these periods. These findings underscore the synchronization between reproductive cycles and behavioral changes, suggesting that hypophagic behavior facilitates energy allocation for reproduction. This may make it possible to estimate the reproductive and physiological cycles of captive loggerhead turtles based on simple behavioral observations that do not cause stress to the turtles, thereby leading to the implementation of successful captive breeding programs.