Dolphins Call Each Other By Name
Bottlenose dolphins use signature whistles when they're separated.
Bottlenose dolphins call out the specific names of loved ones when they become separated, a study finds.
Other than humans, the dolphins are the only animals known to do this, according to the study, published in the latest Proceedings of the Royal Society B. The big difference with bottlenose dolphins is that these communications consist of whistles, not words.
Earlier research found that bottlenose dolphins name themselves, with dolphins having a "signature whistle" that encodes other information. It would be somewhat like a human shouting, "Hey everybody! I'm an adult healthy male named George, and I mean you no harm!"
The new finding is that bottlenose dolphins also say the names of certain other dolphins.
"Animals produced copies when they were separated from a close associate and this supports our belief that dolphins copy another animal's signature whistle when they want to reunite with that specific individual," lead author Stephanie King of the University of St. Andrews Sea Mammal Research Unit told Discovery News.
King and her colleagues collected acoustic data from wild bottlenose dolphins around Sarasota Bay, Fla., from 1984 to 2009. The researchers also intensely studied four captive adult male dolphins housed at The Seas Aquarium, also in Florida.
The captive males are adults that keepers named Calvin, Khyber, Malabar and Ranier.
These bottlenose dolphins, however, as well as all of the wild ones, developed their own signature whistles that serve as names in interactions with other dolphins.
"A dolphin emits its signature whistle to broadcast its identity and announce its presence, allowing animals to identify one another over large distances and for animals to recognize one another and to join up with each other," King explained. "Dolphin whistles can be detected up to 20 km away (12.4 miles) depending on water depth and whistle frequency."
The researchers said dolphins copy the signature whistles of loved ones, such as a mother or close male buddy, when the two are apart. These "names" were never emitted in aggressive or antagonistic situations and were only directed toward loved ones.
The whistle copies also always had a unique variation to them, so the dolphins weren't merely mimicking each other. The dolphins instead were adding their own "tone of voice" via unique whistling.
While researchers often hesitate to apply the "l word" -- language -- to non-human communications, bottlenose dolphins and possibly other dolphin species clearly have a very complex and sophisticated communication system.
"Interestingly, captive dolphins can learn new signals and refer to objects and it may be that dolphins can use signature whistle copies to label or refer to an individual, which is a skill inherent in human language," King said.
Heidi Harley, a professor of psychology at New College of Florida, is a leading expert on cognitive processes in dolphins. She agrees with the new paper's conclusions.
Harley told Discovery News that it can be challenging to study dolphin signature whistles, since it's difficult to identify which particular dolphin is emitting the sounds, and whether or not the sounds are just mimicked copies.
"This study provides evidence that copies of signature whistles include elements that differ from the whistles of the original whistler, while still maintaining the changes in frequency over time that allow a listener to identify the original whistler," Harley said. "In addition, that signature whistle copying occurs between close associates, suggesting it is used affiliatively."
King and her team are now using sound playback experiments to see how wild, free-ranging dolphins respond to hearing a copy of their own signature whistle.
Animal tool use is far more common than previously thought, with fish recently added to the animal tool wielder's list. Here, a green wrasse picks up a clam. The fish later uses a rock as an anvil to smash open the clam. Such underwater cleverness should come as no surprise, according to Culum Brown, director of advanced biology at Macquarie University. "Fish are always ignored when it comes to cognition," he told Discovery News. "That is largely due to our self-centered view of evolution. But even ignoring that bias, we would still seldom study fish because they are simply hard to observe." Added Brown, whose findings are outlined in the latest issue of the journal Fish and Fisheries, "I'm sure tool use is far more common in fish than we realize."
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Fish aren't the only underwater tool users. Dolphins break off sponges and wear them, but it's likely not a fashion statement. "We believe that the marine sponge acts as a kind of glove to protective their sensitive rostra," marine biologist Michael Krützen of the University of Zurich told Discovery News. "That probing (of the sea floor) might disturb fish that hide in the sand, which would then be easy targets for the dolphins."
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Brown believes that "many animals resort to tool use when they lack the physical capability to access a resource, nearly always food, without the specific aid of a tool." This photo shows a selection of sticks altered by chimpanzees at Kibale Forest National Park in Uganda to get at honey and other food.
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Animals may use tools for defense, as does this decorator (also sometimes called "dresser") crab. The crab possesses Velcro-like hooks on its shell that hold "accessories," which in this case are living coral polyps and sea anemones. The other creatures give the crab a bottom-of-the-sea look that helps to disguise it on the reefs where it lives.
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The closer animals are to our own species, the more their tool usage seems human-like. This adult female gorilla named Leah from Nouabalé-Ndoki National Park in northern Congo, turned a big branch into a multi-purpose tool. She used it as a walking stick, for postural support, and to test both the substrate and the water depth. Leah proves three aspects of animal tool usage highlighted by Brown. "First, the animal has to be in an environment where suitable tools are available," he said. "Second, the animal has to have the physical and mental capacity to use the tool. Third, the physics of the environment make tool-use possible." For the latter, he points out that fish don't have hammers because swinging them underwater "is really hard work and not very effective."
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Tools don't always provide the fastest, easiest solution to problems. In the case of New Caledonian crows, for example, their use of sticks to dislodge wood-boring beetle grubs from rotting tree trunks requires a lot of time and practice. Why do crows even bother with the sticks then? Christian Rutz of the University of Oxford and colleagues investigated the benefits of this tool use by analyzing how different types of food contribute to individual crow diets. As it turns out, just a few beetle larvae pulled out by sticks can satisfy a crow's daily energy requirements. So all of the extra effort is worth it.
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Sometimes tools can aid in sudden life or death matters. This small octopus from East Timor was seen on a night dive hiding between a nutshell and a clamshell. When things got quiet, the octopus snuck out, carrying the shells. Sensing threats, it then clamped itself back between the portable hideout.
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One of the most unusual animal tools is a "kiss squeak toy" that orangutans construct out of leaves. Madeleine Hardus of the Behavioral Biology Group at the University of Utrecht told Discovery News that the resulting noise is hardly a love call. Instead, orangutans produce it when predators startle them, or they are otherwise disturbed. "As far as I and my colleagues know, no other primate emits kiss squeak sounds," Hardus said. "Male great apes can use their hands during the production of calls, such as buttress-drumming in chimpanzees, chest-beating in gorillas and snag-crashing in orangutans, but in these examples, calls are not modified; they're added with other acoustic elements. Only kiss squeaks are known to be modified."
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It may not be pretty, but mammal dung serves as a useful tool for burrowing owls. The owls collect the dung and spread it around the entrance to their homes, as seen here. Dung-consuming beetles find the bait irresistible. As the beetles are investigating the fragrant balls, the owl comes out for its crunchy bug dinner.
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Our human ancestors were using stone tools and eating meat from large mammals nearly a million years earlier than previously thought, according to a Nature study that pushed back both of these human activities to around 3.4 million years ago. The first known human ancestor tool-wielder and meat-lover was Australopithecus afarensis, according to the study. This species, whose most famous representative is the skeleton "Lucy," was slender, toothy and small-brained. "By pushing the date for tool use and meat-eating in our lineage back by around 1 million years, our finds show that tool use and meat-eating was not unique to (the genus) Homo," co-author Zeresenay Alemseged told Discovery News. "Also, by showing that A. afarensis was involved in these activities, we showed that you do not need a large brain to do this," added Alemseged, director of the Department of Anthropology at the California Academy of Sciences. Brown agrees that braininess may not always explain how much or little certain species use tools. "Are there physical and or ecological constraints on tool use?" he said. "Hopefully if we do this we can get away from the notion that 'humans use tools so tool-users must be smart like humans.' That idea seems to be leading us in circles."
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