Keeping to a beat is linked to reproductive success in male Rock Hyraxes
IMAGE: A MALE ROCK HYRAX IN THE EIN GEDI NATURAL RESERVE SINGING. view more
CREDIT: AMIYAAL ILANY
A behavioural study published in the British Ecological Society’s Journal of Animal Ecology has linked reproductive success in male rock hyraxes to their ability to maintain rhythm during courtship songs.
You only need to take a look at the adoring fans of famous musicians to realize being rhythmically skilled is a desirable trait. In male rock hyraxes, singing frequency and rhythm could be seen as indicators of individual quality by potential mates – signalling information about their health and suitability as a partner.
“We have been studying hyraxes for the past 20 years and have previously found several patterns in their songs that are common features of human language and music,” said Dr Vlad Demartsev, now a postdoctoral researcher in the Department of Biology at the University of Konstanz and the Max Planck Institute of Animal Behaviour, who collected the data for this study during their time at Tel Aviv University.
“Their songs have regional dialects so individuals living in proximity sing more similarly to each other. They tend to sing in crescendo (getting louder as the song progresses) and reach peak complexity towards the end of their songs, maybe to keep the audience engaged and listening to the signals.”
Rhythm plays a crucial role in the communication of some animals. “One assumption is that rhythm has evolved so that animals that call in groups can better synchronize their songs – like musicians in a band or singers in a choir," explains Dr Vlad Demartsev.
However, unlike many other animals known to communicate through song, hyraxes usually sing alone.
To investigate the role of rhythm in mammalian courtship songs scientists observed the daily morning activity of hyrax communities between 2002 and 2013 in Ein Gedi Natural Reserve, eastern Israel. The researchers captured information about the hyrax's location, behaviours, and vocalizations while recording the identities of their nearest neighbours. Genetic information for each hyrax was then analysed alongside audio recordings back at the lab.
Publishing their findings in the British Ecological Society Journal of Animal Ecology, the researchers showed that, while singing, hyrax males keep a stable isochronous rhythm, with sounds occurring at regular intervals.
Dr Lee Koren, who co-founded the hyrax study with Dr Eli Geffen, and is now a researcher at the Faculty of Life Sciences at Bar-Ilan University said: “Male hyraxes that sing more frequently tend to have more surviving offspring. Song rhythms and stability are related to reproductive success and thus potentially hold information about individual quality.”
Since certain physiological ailments may have a negative effect on the ability of hyraxes to produce precise, rhythmic calls, the researchers suggest male hyrax courtship song rhythm could be an indicator of health and suitability as mates to prospective female partners.
Speaking of the future for this field of research, Dr Vlad Demartsev added: “It would be fascinating to compare animal species who sing individually and species that sing in groups.”
Rhythm has now been shown to act as an advertisement for individual quality in some species, while in others it helps in coordinating signals from different individuals within a group. However, it's not yet known if different rhythmic patterns are used for these two different functions.
CAPTION
A male rock hyrax in the Ein Gedi Natural Reserve singing.
CREDIT
Eran Gissis
CREDIT
Lee Koren
The vocalisations of a male rock hyrax in the Ein Gedi Natural Reserve.
CREDIT
Lee Koren
JOURNAL
Journal of Animal Ecology
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
Male rock hyraxes that maintain an isochronous song rhythm achieve higher reproductive success
ARTICLE PUBLICATION DATE
13-Sep-2022
Keep the beat!
Peer-Reviewed PublicationRhythmic accuracy pays off, as researchers from Konstanz (Germany) and Israel show in their behavioural study on the courtship song of the rock hyrax. Males that sang more often and kept the beat with greater precision had higher reproductive success than their less rhythmically accurate peers.
When it comes to courtship songs in the animal kingdom, most people probably think of songbirds greeting the dawn – to the delight of some and the annoyance of others. But there are also species of mammals in which the males try to charm females by singing. One of them is the rock hyrax (Procavia capensis), a land-living mammal common to the western part of the Near East and to Africa.
In a recent study published in the Journal of Animal Ecology, researchers from the University of Konstanz (Germany), Tel Aviv University (Israel), and Bar Ilan University (Israel), have now taken a closer look at the song of the rock hyrax. They observed the animals in the Ein Gedi Natural Reserve in eastern Israel and recorded their songs, which they later analyzed in the laboratory together with genetic samples from individual males. The researchers focused on the question of whether there is a link between the rhythmic characteristics of the song and the reproductive success of the animals.
Rhythm as a sign of good health
It has been known for quite some time that rhythm plays a role not only in our music but also in the communication of some animals. "One assumption is that rhythm has evolved so that animals that call in groups can better synchronize their songs – like musicians in a band or singers in a choir", says Dr Vlad Demartsev, first author of the study and currently a postdoctoral researcher in the Department of Biology at the University of Konstanz.
From an evolutionary perspective, however, rhythm could also serve the function of signalling the health condition and thus the suitability of the male as a sexual partner to the females. "The reasoning here is that certain physical or physiological limitations inevitably have a negative effect on the ability to produce precise, rhythmic calls", Demartsev explains a second common hypothesis about the evolution of rhythm in animal songs.
In the current study, the researchers were able to show, by combining acoustic analyses and long-term genetic assessment of relatedness, that males with a high proportion of rhythmically precise elements in their courtship song produced more offspring than those with a lower proportion. In addition, males that sang more frequently than their peers had a slightly higher reproductive success.
Since rock hyraxes usually sing alone and not in a choir, it is likely that the aspect of song synchronization did not play a decisive role in the evolution of their rhythmic courtship songs. "The fact that rhythmically stable males produce more offspring rather supports the assumption that high rhythmic stability serves as an indicator of male quality for females and, thus, is particularly attractive to them", Demartsev says.
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Link: https://www.uni-konstanz.de/fileadmin/pi/fileserver/2022/immer_schoen_c_eran_gissis_2.png
Caption: Male rock hyrax singing
Copyright: Eran Gissis
Link: https://www.uni-konstanz.de/fileadmin/pi/fileserver/2022/immer_schoen_c_eran_gissis.png
Caption: Male rock hyrax singing
Copyright: Amiyaal Ilany
A sound file and a video can be found at:
Link: https://soundcloud.com/amiyaal-ilany/rock-hyrax-song
Copyright: Amiyaal Ilany
Link: https://youtu.be/_6uJ53guwMo
Copyright: Eyal Bartov
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JOURNAL
Journal of Animal Ecology
ARTICLE TITLE
Male rock hyraxes that maintain an isochronous song rhythm achieve higher reproductive success.
ARTICLE PUBLICATION DATE
13-Sep-2022
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