Lawrence LeBlond for redOrbit.com – Your Universe Online
Dolphins can perform complex math equations when hunting, suggesting that these animals are far more skilled mathematically than scientists had previously given them credit for, according to new research published in the journal Proceedings of the Royal Society A.
The inspiration for the study came after lead author Tim Leighton, of the University of Southampton, watched an episode of Blue Planet on the Discovery Channel. During this episode, Leighton observed dolphins blowing multiple tiny bubbles around as they hunted, appearing to continue to use sonar.
“I immediately got hooked, because I knew that no man-made sonar would be able to operate in such bubble water,” explained Leighton, a professor of ultrasonics and underwater acoustics at the university, where he is also an associate dean. “These dolphins were either ‘blinding’ their most spectacular sensory apparatus when hunting — which would be odd, though they still have sight to rely on — or they have a sonar that can do what human sonar cannot“¦Perhaps they have something amazing,” he added.
To examine this, Leighton and his colleagues set out to find out if dolphins actually had this amazing ability that humans cannot produce. They started by first modeling the types of echolocation pulses that dolphins emit. They then processed them using nonlinear mathematics instead of the standard linear method of processing sonar returns. Surprisingly, the technique worked, and could explain how dolphins hunt successfully with bubbles.
When hunting, the dolphins blow bubble nets around schools of fish, forcing them to cluster together. The dolphins then count clicks through this mass of bubbles, and are able to pinpoint exactly where the fish are. This ability seems to confirm that they can in fact do complex nonlinear math calculations.
Human sonar systems would be befuddled by the bubbles, even confounding the best man-made sonar because the strong scattering by the bubbles generate “clutter” in the sonar image, which cannot be distinguished from the target.
But somehow, dolphins have a mathematical ability to cancel these bubbles out and find the fish.
The math involved is complex, and relies on sending out pulses that vary in amplitude. The first may have a value of 1 while the second is a third that amplitude.
“So, provided the dolphin remembers what the ratios of the two pulses were, and can multiply the second echo by that and add the echoes together, it can make the fish ‘visible’ to its sonar,” Leighton told Jennifer Viegas of Discovery News, referring to the term as “detection enhancement.”
He acknowledged that it doesn´t end there. There must be a second stage to the hunt.
“Bubbles cause false alarms because they scatter strongly and a dolphin cannot afford to waste its energy chasing false alarms while the real fish escape,” Leighton explained.
So the second stage involves subtracting the echoes from one another, ensuring that the echo of the second pulse is first multiplied by three. The process first entails making the fish visible to sonar by addition. The fish is then made invisible by subtraction to confirm it is a true target.
In order to confirm that dolphins are using such nonlinear mathematical processing, Leighton said some questions must still be answered. In order for the technique to truly work, the dolphins would have to use a frequency when they enter bubbly water that is very low, allowing them to hear frequencies that are twice as high in pitch.
“Until measurements are taken of wild dolphin sonar as they hunt in bubbly water, these questions will remain unanswered,” Leighton noted. “What we have shown is that it is not impossible to distinguish targets in bubbly water using the same sort of pulses that dolphins use.”
If the sonar model can be replicated, it may have significant benefits for humans, allowing for the detection of covert circuitry, such as bugging devices that are hidden in walls or other secretive places. It could also improve the detection of sea mines, and even perhaps land mines.
“Currently, the navy uses dolphins or divers feeling with their hands in such difficult conditions as near shore bubbly water, for example in the Gulf,” he said.
If proven, it will only add to a list of amazing abilities that dolphins already possess. They can recognize themselves in mirrors and can understand ideas such as ℠zero´ — an ability normally restricted to the primate family. They not only know who, or what, they are, but they also have a sense of who, where and what their groups are.
But given their status as being among the most intelligent animals, they are not likely the only math whizzes in the animal kingdom. Parrots and pigeons are also known to have an advanced understanding of numerical concepts, as well are chimpanzees.
Although the study “does not conclusively prove that dolphins do use such nonlinear processing, it demonstrates that humans can detect and classify targets in bubbly water using dolphin-like sonar pulses, raising intriguing possibilities for dolphin sonar when they make bubble nets.”
Leighton and colleagues previously worked with another form of sonar signal: TWIPS (Twin Inverted Pulse Sonar). TWIPS could theoretically work in bubble clouds, consisting of pairs of pulses that were identical except that one was inverted with respect to the other, that could detect targets in bubbly water if the signal processing were to make use of nonlinear mathematics.
However, while TWIPS pulses were successful, Leighton acknowledged there was no conclusive evidence that the types of pulses devised for that study are used by any type of dolphin.
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