Observations of mating behavior of the manta ray,manta birostris, at the ogasawara islands, japan

On 11 July 1997, the mating behavior of wild manta rays,Manta birostris, was observed while skin diving off Chichijima. Ogasawara Islands, Japan, and recorded with 49 underwater photographs and about 20 minutes of video tape. The female manta ray involved was estimated as being approximately 5 m in dise width (DW) and the two males involved, approximately 4 m DW. Copulatory behavior of the two males appeared to be almost the same, copulation itself being of the abdomen-to-abdomen type. Initially, the males chased the female for 20–30 minutes, all animals swimming at approximately 10 km/h. Each copulation event occurred within one meter of the surface, during which time the participating male grasped the tip of the female's left pectoral fin with his mouth. The clasper was inserted for 90 seconds (Male No. 1) and 60 seconds (Male No. 2), respectively. The mating behavior sequence of the manta rays involved following five steps. 1.: Male chases behind the tail of the female, attempting (several times) to grasp the latter's pectoral fin (chasing behavior). 2.: Male bites the tip of the female's pectoral fin, before positioning itself against the latter's underside (biting behavior). 3.: Male inserts a clasper into the cloaca of the female (copulating behavior). 4.: Male removes the clasper from the cloaca of the female, but continues biting the latter's pectoral fin (post-copulating behavior). 5.: Male releases the pectoral fin of the female, setting her free (separating behavior).