Dolphin Update: What Do We Know?
The topic of dolphin intelligence is a never-ending source of wonder, and, according to recent studies, the animals appear to know more and remember more than we thought.
A new study from the Dolphin Research Center in Grass Keys, Fla., appears to indicate that dolphins are smart enough to problem solve in much the same way as humans.
Working with a bottlenose dolphin named Tanner, researchers found he was able to imitate behaviors, even when one of his senses was blocked.
“We already knew dolphins imitate other dolphins, but this time we blindfolded Tanner and used humans instead of dolphins to make the movements in the water,” said Dr. Kelly Jaakkola, research director. “What we found is that he imitated the human movements even when he couldn’t see them.
“The news is that he made a choice,” she said. “When imitating another dolphin he could recognize the sound of the behavior, but when we put a person in the water the sound is different and that’s when he would echolocate.”
Echolocation, or bio sonar, involves sending out sounds and then listening to the echoes that return from nearby objects.
“When we tried to mess him up by blindfolding him and putting a human in the water we saw a whole lot more echolocation going on than when he imitated another dolphin. That is evidence to me of problem solving. This is exciting because Tanner could imitate the human without any learning at all, and that is the first time that has been shown in an animal outside of humans.”
While previous research has shown dolphin intelligence, this one indicates reasoning ability, Jaakkola said.
“People are fascinated by dolphins, and the more we can showcase their intelligence, the more people will get excited about taking care of them,” she said. “This type of study gives us more of a window into their minds, which are not like ours. They’re very different from humans and we’re trying to find out how they are intelligent, and what they are good at and not good at doing.”
Dolphins Never Forget a Whistle
People are also fascinated by the concept of dolphins communicating with one another. Another recent study conducted by a graduate student at the University of Chicago, shows not only do they “talk” to each other, but they remember each other for long periods of time.
It has been known since the mid-1960s that dolphins have individual signature whistles, but now researcher Jason Bruck has demonstrated that dolphins can remember each other’s whistles, even when they have been separated for decades.
“I recorded the whistles from 43 animals in the study,” said Bruck, who recently earned his doctorate in comparative human development. “I then played them back to their former tank mates. I also played unfamiliar whistles for them. For the most part they responded by approaching and whistling to the familiar whistles, but not to the unfamiliar whistles.”
In some cases dolphins even whistled back at the recording, signaling their recognition of the source, Bruck said.
Perhaps most fascinating in Ruck’s study were the dolphins’ abilities to remember each other’s signature whistles after long separations, the longest being 20 years and six months. This is the longest social memory ever recorded for a non-human species, according to the study.
“Their individual whistles are sort of like a hybrid of a name and a face would be to us,” Bruck said. “They don’t see each other as well in the water, and because they work at such distances and in murkier environment, they need these individualized whistles to identify each other.”
Dolphins Share Their Best Tricks
Dolphins are very social animals, a fact not lost on Georgetown University researcher Janet Mann, who has studied dolphin social behavior since 1988.
Skeptics who still wonder if dolphins really do form a circle of friends or confidants need look no further than “Sponging Eve.”
Eve is a dolphin who scratched her nose while looking for food, and figured out if she would just attach a piece of sea sponge to her nose while foraging, that would not happen again. Over the years, Eve spread her sponging technique only to her close friends and family of dolphins, who adopted the behavior along with her.
For 22 years, Mann, a professor of psychology and biology, and her team studied 36 associated dolphins all in the Australia Shark Bay area. In her recently published study, Mann showed that although there were 69 other dolphins in the area, none of them were part of Eve’s inner circle, and none of them learned the sponging trick.
Mann and her team found that not only were dolphins smart enough to pick up a self-protecting behavior, but they also were selective enough to share it with only the dolphins they chose to associate with.
“We suggest that spongers also share in-group identity, but affiliation is a consequence of similarity in the socially learned trait, a scenario that resonates with human culture,” Mann wrote in her study.
Recent Deaths Point to Serious Threat
Officials at the National Oceanic and Atmospheric Administration have declared an unusual mortality event for bottlenose dolphins after more than 100 of the animals have been found stranded in coastal areas in the Mid-Atlantic region since July. Their deaths are still a mystery, but an aggressive effort is being made to determine the cause, since the current event looks strikingly similar to one that claimed 700 dolphins in 1988.
“We’re not at a point of being able to identify the cause yet, but there have been some preliminary samples that tested positive for morbillivirus,” said Mark Swingle, director of research for Virginia Aquarium and Marine Science Center in Virginia Beach, Va. “That was the culprit found in the late 1980s, but there is not enough sampling done yet to declare that as the cause.”
Since the dolphin deaths are so widespread, and there is no evidence of human involvement, such as dolphins hit by boats or entangled in nets, Swingle believes there is clear evidence of a disease process at work.
The search for answers can be time-consuming, especially if the morbillivirus is to blame.
“With a disease process in a wild population, there is no way to do anything about it,” Swingle said. “Typically the disease has to run its course. The animals that survive will then have immunity to the virus.”