Saturday, 4 October 2014


In an amazing experiment with a captive dolphin in Florida Dr. Bruck played a recording of the signature whistle of a 2 year old female to a 25 year old male. The male and female had been together 20 years earlier when the male was only 4 years old. The result? The captive male recognuized the whistle of his female companion after 20 years separation.

So, what does this mean for wild dolphins?

In the wild, dolphins live for about 20 years but many live as long as 45 years. That means that most dolphins are able to remember the "names and identities" through signature whistles of many of the other dolphins they build bonds with.

On the 'memory score card' dolphins rank in the top one or two non-human memory stakes. Only the elephant is said to be able to remember for periods of 20 years or so and we don't know if elephants can remember all the elephants they befriend along the way.

Why dolphins' social memories persist so long is unclear. Dr. Bruck says that dolphins exhibit sophisticated social connections that follow a "fission-fusion" model. Dolphins may separate from one group and "fuse" with other groups many times over. Such relationships could have required a growth in memory capacity to avoid social conflicts. But it's also possible that memory is just one facet of the advanced mind that evolved in dolphins for other reasons.

"Why do they need this kind of memory? I'm not sure they do," Bruck said. "The cognitive abilities of dolphins are really well developed, and sometimes things like this are carry-along traits. But to test whether this kind of social memory capacity is adaptive, we would need more demographic data from multiple populations in the wild to see if they experience 20-year separations."

The emergence of advanced memory in marine mammals as well as in humans shows that in evolution, "there are lots of ways to get from point A to point B," Bruck said. "It's nice to see this kind of ability in a non-primate, as this is a great example of convergent evolution."

"So far no one has been able to test what signature whistles signify in a dolphin's mind. We know they use these signatures like names, but we don't know if the name stands for something in their minds the way a person's name does for us," Bruck said. "We don't know yet if the name makes a dolphin picture another dolphin in its head."

For his next round of research, Bruck said, "That's my goal -- show whether the call evokes a representational mental image of that individual.

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