Jackass Penguin Calls Follow Similar Rules to Human Speech

Nicknamed for their donkey-like calls, “jackass” penguins (Spheniscus demersus) can now boast another claim to mammal-mimicking fame: Their wheezy brays follow speech patterns similar to those found in humans, new research shows.

Some linguists theorize that even though the world’s many languages have produced an array of complex, multisyllabic words and phrases, they tend to be built from short sounds. According to a rule of speech called Zipf’s law, the most common sounds people and other primates produce are short (“the,” “of,” “is”), reports Brandon Spektor for Live Science. And according to another rule called the Menzerath-Altmann Law, the longer and more intricate a vocalization is, the more likely it is to be composed of a string of brief sounds (compare the six-syllable “circumnavigation” to the monosyllabic “strengths”).

Of course, jackass penguins don’t use words, but when they chatter, they still follow both of these linguistic laws, researchers report this week in Biology Letters.

To suss out the specifics of penguin speech, a team led by Livio Favaro, a biologist at the University of Turin, analyzed 590 vocalizations from 28 adult male penguins living in Italian zoos. During their mating period, males are especially outspoken making it the perfect time for the scientists to record. The penguins will often produce “ecstatic display songs,” which are the longest and loudest of their many vocalizations. These songs showcase the sounds that function much like human syllables.

The researchers found that, just as in people, the penguins uttered their briefest calls most frequently, while their longest vocalizations contained the shortest sounds.

Applying linguistics laws outside of human language can get tricky. Zipf’s law and the Menzerath-Altmann law was traditionally applied to written text. Because humans are the only animals that use both verbal and written language, some scholars question whether the two rules would translate across species. Both laws, however, have since been used to analyze verbal language in humans and vocal communication in primates.

Finding that the rule applies to penguins suggests the laws “reflect something deeper and more general about communication and information,” says Chris Kello, a language expert at the University of California, Merced who was not involved in the study, in an interview with Nicola Davis at the Guardian.

In fact, these patterns may be the product of animals’ natural inclination toward efficient communication, allowing them to expend less energy when signaling to others, Stuart Semple, an animal communication expert at the University of Roehampton who was not involved in the study, tells the Guardian. Researchers may yet find these laws reflected in other species whose calls have yet to be recorded and analyzed, Favaro explains to the Guardian.

As for the jackass penguins themselves? They may still be harboring further linguistic complexity. After all, the study only examined one of their many calls, some of which include some saucy posturing, wing spreading and antagonistic pecks.

“Vocalizations have the opportunity to provide a huge amount of information about these birds,” Favaro told Smithsonian’s Helen Thompson in 2014.

These birds aren’t universally chatty, though: When asked to comment, the penguins did not respond.

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.