dolphins blowing bubbles

Learning Mathematics From Dolphins

Dolphins might just be better than humans at mathematics. Researchers have found that these animals might process signals non-linearly to detect target prey.

Bottlenose dolphins use a unique strategy to capture fish, by making what are called ‘bubble nets’. They go around schools of fish in a wide circle in the sea, causing bubbles to spurt at the circumference of this circle. This alarms the fish, who all cluster together at the surface, right into the mouths of the waiting dolphin pack. What we don’t know is- how do these dolphins see their prey in these nets? Man-made SONAR systems cannot work in bubbly regions because the bubbles create a ‘fog’ that confound signals.

dolphins blowing bubbles
a) Dolphins herd sardines using bubble nets. b) A dolphin releases a cloud of bubbles using its blowhole. c) The bubble cloud expands, as the dolphin swims on and other dolphins join in d) The sardines are trapped in a wall of bubbles

[captioning via Leighton et al, 2012. Image Credit: The Blue Planet (BBC)]



Dolphins Have Inbuilt SONAR

Dolphins use echolocation by SONAR (Sound Navigation and Ranging) to detect their prey. They emit sound signals of a certain amplitude and frequency into the water, and use the reflected signals to detect the location of their surroundings, including prey. However, in the vicinity of these bubble nets, the bubbles create too much noise, leading scientists to wonder if the SONAR of dolphins can actually operate in bubble clouds or if dolphins actually ‘blind’ themselves in the process of creating these nets. Man-made SONAR systems which use linear signal processing have been unable to distinguish between bubbles and fish in these conditions.

Mathematicians at the University of Southampton have now used SONAR with non-linear signal processing to see if it can distinguish between fish and bubbles, and it can. Professor Leighton, who headed this research, said, “We know that dolphins emit sequences of clicks and the amplitude of each click can vary from one to the next, so that not all the clicks are the same loudness. We asked, what if this variation in amplitude was not coincidental, but instead was key to distinguishing fish from bubbles. ”

These clicks were shown to identify targets when processed using non-linear mathematics, raising the question of whether dolphins also benefit from such mathematics. The variation in amplitude of these clicks is the key: it produces changes in the echoes which can identify the target (fish) in the bubble net, where man-made sonar does not work. ”

However, in no way does this confirm that dolphins do use the same mechanism. This is simply a way by which they could process signals. In order to detect frequencies in bubble nets, dolphins would have to emit suitably low frequency signals in bubbly waters, and testing this would give an indication of whether non-linear processing is, in fact, how dolphins view their prey. This research could pave the way for new systems in detecting targets like sea mines in bubbly water. For now, it looks like dolphins as master mathematicians might just be the latest addition to the already rich tapestry of dolphin folklore.

More information about this research can be found here.

Published by

Shweta Ramdas

Beginning life as a grad student studying human genetics.