Dolphins have longest memory power: study

Dolphins have longest memory power: study

Chicago (USA) - Dolphins have the longest recorded memory power amongst non-human species, reveals a study by researchers of University of Chicago.�

Dolphin?s level of memory is longest in non-human species and its cognitive sophistication is comparable to humans, chimpanzees and elephants.

?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 PhD in June 2013 from the University of Chicago?s Department of Comparative Human Development.�

Bruck collected data from 53 different bottlenose dolphins at six facilities,�including Brookfield Zoo near Chicago and Dolphin Quest in Bermuda to establish how well dolphins could remember their former companions. 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 where you know how long the animals have been apart,? Bruck said. ?To do a similar study in the wild would be almost impossible.?

In recent years, studies by other researchers have established that each dolphin develops a 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 methodical comparison of how they responded to familiar calls versus calls belonging to dolphins they had never met.

First, 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 with which the target dolphin had lived.�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.?

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

The studies revealed, dolphins responded significantly to whistles from animals they once knew, even if they had not heard the calls in decades. Bruck concluded dolphins maintained lifelong memories of each others? whistles. In the wild, bottlenose dolphins have an average life expectancy of about 20 years, though longer-lived creatures can survive up to 45 years or more.

Exactly why dolphins? social memories persist so long remains unclear. Dolphins exhibit sophisticated social connections that follow a ?fission-fusion? model. In the open ocean, dolphins may break apart from one group and ?fuse? with other groups many times over. Such relationships could have required a growth in memory capacity. But it?s also possible that memory is just one facet of the advanced mind that evolved in dolphins for other reasons.

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