![]() However, the resonance of the human male voice is actually higher than predicted for a terrestrial mammal weighing 75 kg (the average weight of a human male). Previous research shows that the lower fundamental frequency and formants of the human male voice contribute to mate choice, and that the secondary descent of the larynx in human males at puberty (which allows them to make calls with even lower formant frequencies) also evolved to exaggerate body size. The researchers say that the current study provides a useful introduction for studying our own species' vocal communications. ![]() Larger testes produce more sperm and so would be an advantage in sperm competition. This can happen through physical removal of a competing male's sperm, guarding the female so that she doesn't mate again, or simply producing more and stronger sperm. Sperm competition occurs when a female can mate with multiple partners, which forces the sperm of different males to compete to fertilize the female's egg. In contrast, males with larger testes relative to body size but higher resonance calls were found in species where sperm competition occurs. Their results showed that general acoustic allometry holds across the different mammalian orders: larger species produce calls with lower fundamental frequencies and lower formants. They also found that in the species where females actively preferred larger males, these males produced calls with lower resonance than expected for their body size. Sexual dimorphism or relative testes size were included in the model depending on the hypothesis being tested. They started with a "global" model that included male body mass, habitat (arboreal or terrestrial), call type (sexual or non-sexual), and mating system (polygynous, monogamous, polyandrous, promiscuous, or variable) of 72 species of terrestrial mammals. The researchers used phylogenetic generalized least-squares (PGLS) regression models to simulate five different evolutionary scenarios. ![]() But while this assumption has been tested in a small number of species, the current study is the first one to see if this assumption is true across a broad range of mammalian groups. Sounding bigger than they actually are gives males in this situation a distinct advantage. Examples of these are the fleshy vocal pads of male lions and tigers that enable them to release ear-splitting roars.īecause these physical features are often only present or more pronounced in males and are often used for mating calls, scientists have assumed that these traits evolved because of mate selection pressures where females only mate with the larger-and therefore presumably stronger-males. In these species, males have special physical adaptations that allow them to sound bigger than they actually are. Some exceptions to the rule do exist, typically in the males of the species. ![]() As researchers Benjamin Charlton and David Reby describe it, "Larger animals tend to produce lower-pitched calls than smaller ones because they have larger larynges with longer vocal folds that can oscillate periodically at lower frequencies, longer vocal tracts that produce lower resonances". How deep or resonant an animal call is is largely a function of the animal's body size. The study was conducted by researchers from University College Dublin and the University of Sussex and published in the journal Nature Communications. A study surveying 72 species of terrestrial mammals belonging to nine orders revealed that the males of species that exaggerate their body size by having lower-than-expected calls have smaller testes compared to males of species with similar body size that engage in sperm competition. Having a deep sexy voice doesn't necessarily mean you're virile, at least as far as mammals are concerned.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |