A new study that came out Tuesday published online in the journal “Proceedings of the Royal Society of London B”, under the article “Decades-long social memory in bottlenose dolphins,” shows that the memory of bottlenose dolphins can span at least 20 years. The study was cross institutional, but was put together by Jason N. Bruck of the Department of Comparative Human Development, Institute for Mind and Biology, University of Chicago.
Prior to this study, much of what we knew about dolphin memory was shallow and anecdotal. Now, however, this study shows that these mammals can recognize their old companion’s signature whistle, even after 20 years apart.
Bruck studied 56 bottlenose dolphins that were moved between six institutions, including Chicago’s Brookfield Zoo, the Minnesota Zoo and an aquarium at Disney World in Orlando. The longest period between two dolphins having either been with or even heard the signature call of another tank mate was 20 years. The movement of these dolphins between facilities were typically for breeding purposes, which somewhat mimicked the shifts among pods of dolphins in the wild.
This study was possible due to the fact that Bruck had a record of the dolphin’s social histories, something which would be nearly impossible in a field study. Burck stored all the dolphins’ signature whistles and broadcast them through an underwater speaker, noting the dolphins’ reactions.
“If you took our names and our faces, merged them into one thing, that would be the best way to describe a signature whistle,” he said. Dolphins choose this “name” for themselves while they are 4 months to a year old.
In order to rule out the dolphin reacting to some random noises, Burck first played a set of unfamiliar whistles. Once the dolphins were accustomed to the speaker, he played a familiar whistle, which resulted in a dolphin quickly approaching the speaker, even if it realized another dolphin wasn’t there.
One female dolphin named Allie, currently at the Brookfield Zoom, last lived with Bailey, a female now in Bermuda, more than 20 years ago. Upon hearing Allie’s whistle, Bailey recognized the sound, according to the research.
This research supports the understanding that dolphins, amongst chimpanzees and elephants, are another animal on this planet that posses a long term memory. In light of this fact in conjunction with the large brain, the social and sexual habits of dolphins being so close to humans already, it is no wonder that India granted dolphins non-human personhood earlier this year.
India declared cetaceans, both whales and dolphins, non-human persons with rights and privileges in May of this year. Ruling that it would thus be morally unacceptable to keep them in captivity, the Government of India has declared that all dolphin parks recently opened will close and that all projects for further dolphin projects are to be shelved. It also makes it now illegal to capture or confine cetacean species.
It is not surprising that as we learn more and more about the other inhabitants of this planet, that we discover more and more animals that have habits and traits in common with us. It would seem that this additional piece of information about dolphins just goes to reinforce the understanding of some, that we have never been alone on this planet, but we are only beginning to recognize the other intelligent creatures upon it.
Written By: Iam Bloom