If I had to guess I would say they trapped some squid against the rocks but I didn't want to get get too close to see. The baby was cute swimming along very close to the mom. I wish I had my other camera with the bigger zoom lens.
The South Shore of RI is loaded with Big squid. I got into decent fish yesterday and the one I kept had 3 or 4 big squid in it's gut. These were fresh, still purple and about 8 - 9" long. My bet is the dolphins are feeding on Squid.
I saw what looked like the same species in the Falmouth area yesterday. It was a baby that had been separated from the rest of the pod. It was cruising up and down the beach probably looking for mom when a marine mammal rescue team showed up. They basically just kept an eye on it.... said that without its mom its odds of making it were slim to none. Very interesting sight to see.... pretty sad situation.