How male rock hyraxes woo potential mates

Mammals bellow, roar, screech, sniff and bark, but few can be said to sing. With a few exceptions – gibbons, indri lemurs, whales and hyraxes – singing is reserved for birds. New research shows that, in the case of male song hyraxes, they also have rhythm. And the more rhythmically accurate their singing, the more offspring they produce.

Rock hyraxes are not nightingales. The vocalizations they put out during the mating season – a harsh combination of growls, barks and squeaks – are classified as songs because of their complexity, not their beauty.

“The song is quite unique for a mammal,” says Vlad Demartsev, lead author of the new study published in the Journal of Animal Ecology. “It’s very long and structured in fights. They play a sequence of sounds, then stop for a second and start again – pause, start, pause, start and so on for five or six minutes.

Working on rock hyraxes in the deserts of eastern Israel, Demartsev and his colleagues analyzed the time intervals between neighboring notes within each bout. “They’re almost identical – very accurate,” he says. “If they start slow, they stay slow for the rest of the fight. And if they start fast, they stay fast, until they finally reach a complex and climactic end.

And the degree of rhythmic consistency seems to indicate a male’s attractiveness to females, because the males that kept the rhythm most precisely sired the most offspring.

“Rhythmic display could be a reflection of a man’s quality as it requires precise muscle control and coordination,” says Demartsev, who is based at the German University of Konstanz.

The findings may also have implications for the origins of human music. One theory is that the rhythmic components of songs evolve to allow synchronization between individuals singing together in chorus – in gibbon duets, for example. But hyrax work suggests it can also arise in solo performers who advertise their quality to potential partners.

Main image: Rock Hyrax in Israel. © Dimitri Feldman/EyeEm/Getty

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