Category Archives: science news

Want to Understand Dolphin Echolocation, Talk to A Biologist

It looks like a story about the [mathematical ability of dolphins][] has caught the attention of many. (See for example the [HuffPo][], [Discovery News][], [MSNBC][], and [the Examiner][].) Everyone loves dolphins, and it wouldn’t surprise anyone that dolphins are doing sophisticated mathematics. They are very very intelligent mammals, after all. But there are two things wrong with the story, or maybe with the way the story is being described.

First, the apparent use of mathematics by animals is an old trope, though. A few years ago, people were excited about a [dog that uses Calculus][] when chasing a thrown ball or frisbee. It looked to an observer that this dog was ‘computing’ an optimal solution to intercepting the ball in flight. The path the dog ran was like the solution to a complex optimization problem that would require Calculus for a person to solve. But dogs don’t do math. Mathematics is a human invention. It is a formal language. Dogs accomplish this through practice, much like professional athletes (many of whom don’t do math, either, and certainly don’t use math while in competition).

Second, the researchers are interested in the way dolphins are able to echolocate prey in the vicinity of the bubble nets dolphins create to herd fish. Without citing knowledge from the biology literature, they compare the dolphin’s sonar ‘technology’ unfavorably with that of human technology.

Taking a dolphin’s sonar and characterising it from an engineering perspective, it is not superior to the best man-made sonar. Therefore, in blowing bubble nets, dolphins are either ‘blinding’ their echolocation sense when hunting or they have a facility absent in man-made sonar.

I’m waiting for a copy of [the paper][], so this criticism is based on the press release, but the above leap of logic is weak. Take insectivorous bats, which also hunt using echolocation based on making rapid clicks. Species that inhabit boreal forests, for example, hunt in cluttered environments. Their adaptive technique for overcoming clutter is to emit clicks that sweep a range of frequencies. Higher frequency clicks reflect off of small pieces of clutter, and low frequency clicks reflect of larger objects. This allows bats to hunt, identify, and eat prey in clutter. And in the dark.

If you ask someone which beast is cuter, a bat or a dolphin, few will go with the bat. So it’s no surprise that this story about dolphins is making a splash. (Couldn’t help the pun.) And there’s no denying that the dolphin hunting technique of corralling fish with bubble nets is beautiful and awesome. This science news that people are getting excited about is probably neither.

**Note**: As I was about to post this, the Media Relations folks at the University of Southampton emailed me a link to the paper. I’ve linked it to the text, above.

**Update**: A preliminary look at the paper shows they do cite the biology literature and, perhaps, to use a more sophisticated model for the echolocation sounds made by dolphins.

[mathematical ability of dolphins]: http://www.southampton.ac.uk/engineering/news/2012/07/18_dolphins.page?
[HuffPo]: http://www.huffingtonpost.com/2012/07/23/dolphin-math-signal-processing_n_1686301.html
[Discovery News]: http://news.discovery.com/animals/dolphins-math-geniuses-120717.html
[MSNBC]: http://www.msnbc.msn.com/id/48218696/ns/technology_and_science-science/?__utma=14933801.273587157.1342460138.1342558535.1342619252.4__utmb=14933801.3.10.1342619252__utmc=14933801__utmx=-__utmz=14933801.1342619252.4.4.utmcsr%3Dmsn.com%7Cutmccn%3D(referral)%7Cutmcmd%3Dreferral%7Cutmcct%3D/__utmv=14933801.%7C8%3DEarned+By%3Dmsnbc%7Ccover%3D1
[the Examiner]: http://www.examiner.com/article/dolphins-may-help-military-find-mines-by-using-mathematics
[dog that uses Calculus]: http://www.maa.org/mathland/mathtrek_06_09_03.html
[the paper]: http://rspa.royalsocietypublishing.org/content/early/2012/07/17/rspa.2012.0247