Risso's dolphins are noted for their bulbous heads marked by a vertical crease. Photo by Wikimedia Commons
March 1 (UPI) -- Risso's dolphins are planners. According to new research, the unique dolphin species coordinate their dives, using learned information to inform their next dive strategy.
Because dolphins are mammals and breathe oxygen, they have a finite amount of time underwater tracking down something to eat. Therefore, they must be efficient. Luckily, they boast impressive cognitive abilities in addition to their speed and agility.
"Lab experiments that test the memory of animals for the location of food show that they have a similar ability to that of humans," Patricia Arranz, a research biologist at the University of St. Andrews in Scotland, said in a news release.
Given their social nature and advanced cognition, scientists hypothesized that dolphins boost the efficiency of their foraging missions -- their dives -- by planning ahead.
To find out if such a hypothesis could be confirmed, an international team set out to track and analyze the foraging patterns of Risso's dolphins, a species noted for its bulbous head marked by a vertical crease. Tracking dolphins, however, is no easy task.
"It is really difficult to approach them and attach something to their backs; you need to be very patient!" said Arranz.
Scientists were able to tag a single Risso's dolphin. In addition, the researchers used remote controlled submarines outfitted with echosounders to track the movement and communications of dolphin groups and the shoals of squid they were after.
"In one of the experiments, we were extremely lucky as the group that the tagged animal was in stayed in the same area, allowing us to track the dolphin every time it was at the surface and observe the prey with the echosounder right where and when the dolphin was foraging," said Arranz.
Back in the lab, scientists analyzed the data collected during their surveys. They found the dolphins began echolocating as soon they left the surface and commenced diving, most likely to gain realtime information about their hunting environs -- the movements of prey, the contours of the habitat below. They also found the dolphins matched their echolocation range to the depths where they had encountered the most squid on their previous dive.
As Arranz and her colleagues argue in a new paper published in the Journal of Experimental Biology, this coordination of echolocation can be interpreted as using learned information for the planning of the next dive.
The research suggests dolphins are quick thinkers and can marry pre-planning with new information gleaned on the go. Often, dolphin groups began dives looking for squid at a certain depth, but later turned their attention to larger shoals of squid at deeper depths.