Keeping a beat is linked to reproductive success in male rock hyrax

A behavioral study published in the Journal of Animal Ecology has linked reproductive success in male rock hyrax to their ability to maintain rhythm during courtship songs.

You only have to look at the adoring fans of famous musicians to see that rhythmic ability is a desirable trait. In male rock hyrax, song frequency and rhythm could be viewed by potential mates as indicators of individual quality – they signal information about their health and suitability as mates.

“We have studied rock hyraxes for the last 20 years and previously found several patterns in their songs that are common features of human language and music,” said Dr. Vlad Demartsev, now a postdoctoral fellow at the Institute of Biology at the University of Konstanz and the Max Planck Institute for Animal Behavior, who collected the data for this study during their time at Tel Aviv University.

“Their songs have regional dialects, so people who live nearby sing more similarly. They tend to sing in crescendos (getting louder as the song progresses) and reach peak complexity towards the end of their songs, perhaps to keep the audience engaged and listening to the cues.”

Rhythm plays a crucial role in the communication of some animals. “One assumption is that rhythm evolved in such a way that animals calling in groups are better able to synchronize their songs – like musicians in a band or singers in a choir,” explains Dr. Demartsev.

However, unlike many other animals that are known to communicate through song, rock hyraxes usually sing alone.

Between 2002 and 2013, to study the role of rhythm in mammalian courtship songs, scientists observed daily morning activity of rock hyrax communities in the Ein Gedi Nature Reserve in eastern Israel. Researchers collected information about each rock hyrax’s location, behavior and vocalizations while recording the identities of their nearest neighbors. Genetic information for each rock hyrax was then analyzed in the laboratory along with audio recordings.

By publishing their results, the researchers showed that male rock hyraxes maintain a stable isochronous rhythm when singing, with tones occurring at regular intervals.

dr Lee Koren, who along with Dr. Eli Geffen, who founded the Rock Hyrax study and is now a researcher at the Faculty of Life Sciences at Bar-Ilan University, said: “Male rock hyraxes that sing more often tend to have more surviving offspring. Song rhythms and stability are related to reproductive success and therefore may contain information about individual quality.”

Because certain physiological conditions can negatively impact rock hyrax’s ability to produce precise, rhythmic calls, the researchers suggest that the male rock hyrax’s courtship song rhythm may be an indicator of health and mate suitability for potential female mates.

Regarding the future of this research area, Dr. Vlad Demartsev adds: “It would be fascinating to compare animal species that sing individually and species that sing in groups.”

It has now been shown that rhythm acts as an advertisement for individual quality in some species, while in others it helps coordinate signals from different individuals within a group. However, it is not yet known whether different rhythmic patterns are used for these two distinct functions.