Much socializing ... or possible theft?
Today was my last day on the water for my field work this summer in Japan. While the dolphins were not interested in swimmers or the boats, it was still a great day (any day on the water is great!). Mostly the dolphins seemed to be resting, but one group was highly active with much rolling and splashing observed at the surface. This group also contained a brand new calf!! It bobbed above the others ever so often. It is #032's (Atokake's) calf. It was probably born on 7/11/00 because I have video of Atokake on Monday and pregnant.
Some colleagues of mine who study captive dolphins have indicated that subadult and adult female dolphins may attempt to steal away a new calf for their own. This has been anecdotally reported in the wild as well. It is possible that the surface activity we saw was representative of this type of behavior. The calf was seen swimming with subadult females, as well as #032, in the 'P2' position - to the side of the larger body near the dorsal fin.
I was able to get video clips on the morning trip but not the afternoon trip. It seems we observed mostly mother/calf groups with juveniles and sub-adults in the morning. These groups had dispersed in the afternoon. Smaller groups and more rest behavior at the later time.
What an exciting last day on the water!