Saturday, September 15, 2012

Back on the Water!

After three days off the water due to bad weather, we finally got a break today and were able to survey this afternoon. The first dolphin encountered was Jpeg, an older female in the population who we had seen on previous days with a calf who was likely born early this summer (judged by size). This time, the calf was no where to be seen and Jpeg was busy feeding. 

Jpeg diving while searching for fish

We were a bit crestfallen wondering if something had happened to the calf. Jpeg eventually moved towards another group of dolphins (a group that was about 100m away in a tight formation), and low and behold, there was her calf. The calf reunited with Jpeg and they continued to travel next to one another for the rest of the time we got to spend with this group. This behavior had been noted on one other day, where we found a large group of dolphins and the Jpeg's calf surfaced instead near another female who is still too young to start reproducing. Eventually the group came into contact with Jpeg who then, as she did today, reunited with the calf and then continued to travel next to it.

This behavior, separation from such a young calf, is rarely noted, but does occur in some cetaceans. For example, in sperm whales, calves are not big enough to dive to the depths where food for this species is located (giant squid). So when the mother dives for food, the calf is left at the surface. This can be a risky position to be in, as killer whales tend to prey on sperm whale calves. To remedy the situation, other females in the group will stay with the calf (“baby sitting”) until the mother comes back to the surface.

In the Key West population, we rarely see such young calves so far from their mothers. In many groups, calves will move away from the mom and interact with others group members or come over to our boat to check us out, but do not move so far that the researchers could not locate both mom and calf in sighting distance of the boat. In addition, we have never seen Jpeg do this with her previous calves. It could be that this particular calf is more gregarious. It could also be that Jpeg is hungrier and needs to break from the group to feed while others are busy socializing (which is the activity that was occurring in the group where her calf was noted, with the calf at the center of a lot of the activity). 


Jpeg's gregarious calf, playing near other adult dolphins

We will continue to monitor Jpeg's behavior, especially because we also believe her last calf may not have survived. It was born in October of 2010, and should have been almost 2 now. Usually calves in our population stay with moms for over 2 years. It is possible that the October 2010 calf had separated from her, but we were not able to document it, or to relocate it in the population yet this season.

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