Female humans aren't the only species that finds deep-voiced males attractive.
Female fallow deer, or does, are also attracted to males with a more rumbling timbre, a new study finds.
Male deer, or bucks, make a deep groaning noise during the October mating season, called the rut. Bucks groan at both females and other males, and can make up to 90 calls a minute.
Research reveals that bucks with the most resonant groans are usually dominant members of the herd—and as a result, are the most popular with does.
What's more, the groans are related to body size: In general, the deeper the groan, the bigger the buck.
The research is detailed online this week in the journal PLoS One.
Voicebox Variances
Scientists recorded the groans and measured sizes of dominant bucks in Dublin, Ireland, for six years.
The findings prove for the first time that a non-primate mammal species can use calls to signal social dominance, the researchers say.
Like humans, deer have a descended larynx, also called a voice box.
"The descended larynx means that animals have a longer vocal tract above the larynx, and therefore [deeper voices]," Alan McElligott of Queen Mary, University of London, said in an email.
The larynx of most mammals, as well as human infants, is situated very high in the throat, allowing them to eat and breathe at the same time.
Anthropologists have argued that the descent of the larynx in humans was an important precursor to the evolution of human speech because it gives the tongue more freedom of movement.
(Explore the human body.)
But the new study supports an alternative—although not mutually exclusive—explanation.
The descended larynx gives both male deer and humans deeper voices than would be expected from just their body size alone. In effect, it gives both species the longer vocal tract of much larger animals.
Some scientists have thus speculated that the descending larynx in humans first evolved as a way for men to attract women.
(Learn about mating rituals in other species.)
Consistent Findings
The new findings on fallow deer are consistent with this idea, said Tecumseh Fitch, an evolutionary psychologist at the University of St. Andrews in Scotland.
"This strengthens the hypothesis that the original function of the human descended larynx was size exaggeration, rather than increased speech performance," said Fitch, who was not involved in the research.
David Reby, a biologist at the University of Sussex in the United Kingdom, also does not think the similarities between human and deer are a coincidence.
"Such a convergent, yet independent, evolution is highly suggestive of a common cause," Reby said.
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