Saturday, May 13, 2006

How do calves learn?

One July day in the field, we got another little piece of the puzzle of dolphin behavior: How little calves learn the ways of their watery world.We start our dolphin surveys as the morning sun reaches the horizon. Yesterday, we set off later than usual.

The night before had been wild with winds and rain from a giant storm in the Bahamas, so we launched when it was light.In a shallow cove about half way through the study area, we happened upon the late breakfast of a mother dolphin named X and her calf Little X. Little X is probably 6 to 7 months old. It long ago mastered the art of swimming and nursing. It has grown plump on X's rich milk. It still has the big adorable head that marks it as a baby mammal.

Little X's behavior is even cuter. We often see a particular behavior in mom dolphins with small calves: Mom feeds while her calf, which doesn't yet eat solid food, plays nearby. It is like a human mother eating her fast-food breakfast on a bench watching her toddler lope around. Only with dolphins, though, mom's breakfast really is fast food.Mom dolphin roams a small area in search of fleet fish and crabs. She is under the water most of the time.

You can't predict where she will surface, but she stays in a general area.We park the boat to one side and watch for intermittent silhouettes. While mom dolphins look for food, dolphin babies try out new behaviors (not unlike human kids at the grocery store). Dolphin calves this age pick a couple of behaviors and do them over and over. We watched Little X calf practice the wonders of body wiggling, tailslapping, blowing bubbles, swimming up-side-down, rearing up over the surface and even standing up in the water (spyhopping). It's so fun to be a baby dolphin.

Dolphin calves are not only active. They are also very curious. Depending on their courage, they sometimes approach the boat close enough to satisfy the most ardent dolphin observer. Then they zoom away, only to return to tease us some more. Oh, are they fun to watch but hard to film.The puzzle piece we learned today was that whenever Little X came too close the boat, X hurried over, retrieved it and escorted it away.Retrieving is when a big dolphin zooms by a smaller dolphin and sweeps it up into its jet stream.

If the big dolphin keeps swimming fast, the little one is swept into the echelon position next to the big dolphin. Then the big dolphin can take the little dolphin where it wants.What was so interesting about our observations was that X let Little X hang around our boat as long at it didn't get too close to us. When Little X got too close, X zoomed in and took it to a safer distance.

Only then would she return to feeding. She did this repeatedly. She was teaching Little X about the distance to maintain from boats. Some dolphins are boat-friendly; they don't seem to mind boats. Some are not. This varies a lot among the dolphins; they have individual personalities and attitudes just like people do. Before X had her calf, she was more boat-friendly! Now, X is clearly an attentive and responsive mom. What does X understand about the dangers of a boat to her baby?

Quick "Facts about Dolphins"