Dr Gerry Goeden's Swimming With Dolphins: elephant

Saturday, 4 October 2014

CAPTIVE DOLPHIN REMEMBERS FRIENDS AFTER 20 YEARS

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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Tuesday, 23 September 2014

DOLPHIN MEMORY AND INTELLIGENCE

New research reveals that dolphins can recognize the whistles of old "tank mates" after a separation of 20 years.This is the longest social memory recorded for any species other than humans.

The remarkable memory is another indication that dolphins have a level of cognitive ability comparable to only a few other species, including humans, chimpanzees and elephants. Dolphins' talent for social recognition may be even more long-lasting than facial recognition among humans. This is because human faces change over time but the signature whistle that identifies a dolphin remains stable over many decades.

"This shows us an animal operating cognitively at a level that's very consistent with human social memory," said Jason Bruck, who conducted the study and received his Ph.D. in June 2013 from the University of Chicago's program in Comparative Human Development. His study is published in the current issue of the Proceedings of the Royal Society of London B.

To establish how well dolphins could remember their former companions, Bruck collected data from 53 different bottlenose dolphins at six facilities, including Brookfield Zoo near Chicago and Dolphin Quest in Bermuda. The six sites were part of a breeding consortium that has rotated dolphins and kept records on which ones lived together, going back decades.

"This is the kind of study you can only do with captive groups when you know how long the animals have been apart," Bruck said. "To do a similar study in the wild would be almost impossible."

"Signature whistles" offer means to test memory

Other studies have established that each dolphin develops its own unique signature whistle that appears to function as a name. Researchers Vincent M. Janik and Stephanie L. King at Scotland's University of St. Andrews reported earlier this year that a wild bottlenose dolphin can learn and repeat signatures belonging to other individuals, and answer when another dolphin mimics its unique call.

Bruck played recordings of signature whistles to dolphins that had once lived with the animals that made the calls. Determining whether the dolphins recognized their old companions required a comparison of how they responded to familiar calls versus calls belonging to dolphins they had never met.

Bruck would play recording after recording of signature whistles that the target dolphins had never heard before. His initial studies showed that these "dolphins get bored quickly listening to signature whistles from dolphins they don't know." Once they were habituated to the unfamiliar calls, Bruck would play a recording of an animal that he knew the target dolphin had lived with.

The familiar calls often would perk up the dolphins and elicit an immediate response.

"When they hear a dolphin they know, they often quickly approach the speaker playing the recording," Bruck said. "At times they will hover around, whistle at it, try to get it to whistle back."

To check that the response was the result of recognition, Bruck also would play a test recording of an unfamiliar bottlenose that was the same age and sex as the familiar animal. All the behavior was scored according to how quickly and to what degree the animals responded.

A clear pattern emerged in the data: Compared with unfamiliar calls, dolphins responded significantly more to whistles from animals they once knew, even if they had not heard the calls in decades.