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Abstract: In March 2015, we observed mating behavior of loggerhead turtles in the western coastal waters of Okinawa Island, Japan. Two males and one female were initially involved, of which one of the males (M1) was attempting to mount the other male (M2) that had already mounted the female. Shortly after the onset of observation, M1 dismounted from M2 and swam away. At that time, the female, initially seemingly resisting copulation with M2, became receptive. This is the first report of loggerhead turtle mating behavior that involves more than two individuals. This observation suggests that the mating season of loggerheads around Okinawa Island includes the early spring.
Key words: Caretta caretta; Estrus; Mating behavior; Mating period; Okinawan Waters
Loggerhead Turtles, Caretta caretta, are distributed in tropical and subtropical marine areas worldwide (Pritchard, 1997). Prior to the start of their reproductive season, sea turtles, including loggerhead turtles, generally migrate from their foraging area to coastal waters near the nesting area, where they lay their eggs and mate (Miller, 1997). During the nesting season (from spring to summer), reproductive females emerge onto sandy beaches, and oviposit several clutches of eggs (Miller, 1997). Okinawa Island has several sandy beaches used for oviposition by logger-head turtles (Kikukawa et al., 1999; Uchida, 1985).
Adult loggerhead turtles that migrate to Okinawan waters include individuals in an active reproductive state (i.e., spermatogenic and vitellogenic turtles) (Kawazu et al., 2013). Nevertheless, with the exception of a few sporadic observations within a reef off Amamioshima Island (Oki, 2001) and in the coastal waters of Okinawa Island (Kawazu and Okabe, 2014; Takahashi et al., 2016), there has been no direct evidence that loggerhead turtles mate in Japanese waters.
On March 21, 2015, we came across one female and two male loggerhead turtles in the western coastal...