Hyraxes, which resemble rodents but are more closely related to elephants or manatees, often cluck, snort, squeak, tweet and wail songs from the perches of their rocky colonies.
By recording hundreds of the animals’ songs and applying clever mathematics, researchers discovered that differences in note arrangement, or syntax, in hyrax songs vary as the distance increases between colonies — a surprising occurrence of dialect.
“Dialect is usually seen only in animals with sophisticated vocalizations, like primates, bats and cetaceans. Such animals can copy and improvise on what they hear, which are very, very core building blocks of language,” said zoologist Arik Kershenbaum at the University of Haifa in Israel.
“It’s not obvious to human ears, but hyraxes also appear to have these building blocks,” said Kershenbaum, who co-authored the study of hyrax songs Apr. 18 in Proceedings of the Royal Society B.
Most hyraxes live in central Africa, southern Africa and parts of the Middle East. In Israel the rock hyrax is a pekingese-dog-size species, called Procavia capensis, which dominates the craggy landscape in colonies numbering from as small as 10 to as large as 50.
Like meerkats or prairie dogs, hyraxes keep lookouts while the colony forages. If the lookout spots a threat, he sings and the colony retreats into the rocks. Such songs may also be used as distress calls, in territory maintenance, male status claims and mating.
Songs are composed of bouts, which are made of 20 to 30 syllables. Hyraxes sing a bout, take a breath and then repeat.
“Songs can go on for 10 minutes or more and are quite enchanting and eerie,” Kershenbaum said. “In Israel we’re surrounded by hyraxes, and one morning while listening I thought, ‘There is no way these sounds are random. Evolution doesn’t favor random complexity like that.’”
To explore the rock hyrax’s syllabic singing, Kershenbaum and his colleagues toured nine sites across Israel and recorded more than 200 hyrax songs for a total of nearly 3,000 bouts. The team then codified bouts into strings of letters representing each of the five sounds and its order, like base pairs in the genetic code of DNA.
Mathematical algorithms, including one normally used to express the similarity of one string of DNA to another, revealed surprising changes in song syntax. The differences jumped as the distance from one colony to the next increased. Closer colonies sang songs in roughly similar orders, for example, while hyraxes in distant colonies sang songs with relatively jumbled notes.
“It’s not the kind of thing you can really detect by ear, if you’re not a hyrax, but these songs are phenomenally complex. The differences are quite subtle but consistent,” Kershenbaum said.
The researchers don’t yet understand what hyraxes use such hidden complexity for, if anything, but Kershenbaum plans to sample the rest of the animal kingdom for hidden syntactic dialects.
Read more at Wired Science
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