It is hard to be attentive to all the information that is around us; we need to focus on particular signals or sensory channels to get more details. This is why alerting signals are frequently used in human communication: for example, calling “hey” before addressing another person or sounding a chime before announcements at train stations and airports.
We can find these alerting components among animals as well – signals whose primary function is to draw conspecifics’ attention to what they are about to communicate. “As an animal, this is even more crucial because you always need to monitor your environment. Otherwise, you’ll miss food opportunities or fail to notice predators”, says behavioural ecologist Vlad Demartsev. This is why alerting signals make communication more efficient – for the receivers, as continuous focused attention on one, specific signal reduces their capacity to monitor their environment. And for the signallers, the alerting signals ensure that the core message, which may be costly or risky to produce, is received.
Vlad Demartsev, a post-doc at the Cluster of Excellence “Collective Behaviour” at the University of Konstanz and the Max Planck Institute of Animal Behavior, and his colleagues from Tel Aviv University and Bar-Ilan University introduce a framework to test animal signals for their alerting function in a paper recently published in the journal Animal Behaviour. In a second step, they applied this framework to find out whether the introductory notes (“wails”) in rock hyraxes’ songs met the criteria for such an alerting function.
Clues to an alerting function
The proposed framework is based on examining three tiers: the signal itself, the signaller and the audience. To begin with, an alerting signal is expected to be heard from greater distances and resist being drowned out by environmental noise. Do signallers use the component flexibly – e.g. omit it if receivers react to it, or repeat it in case of environmental noise? And on the listening side, does the signal affect the receivers in a predictable way, increasing the likelihood and speed of their responses? “The phenomenon of alerting signals is likely widespread among animals”, says Demartsev, “but so far, we haven’t had a systematic method to examine it.”
Rock hyraxes are social mammals with a well-described vocal repertoire. Their songs are complex with much information encoded in them, and as singing mammals, they are quite unique. Male hyraxes may use the songs to advertise themselves to potential female mating partners and assess competitors. It is thus crucial for them to be heard, whereas the costs may be high, if they are detected by predators or aggressive rivals.
Rock hyrax songs are arranged in sequences of three distinct vocal elements. These include “wails” that Demartsev and his colleagues hypothesize might have an alerting function, as they are the opening elements in songs and frequently subside as songs progress. Moreover, wails are not correlated with the male animals’ traits like age or rank – unlike other vocal elements.
Hey, listen to me
The question is: How did the researchers assess whether wails potentially serve an alerting purpose? First of all, they analyzed all the song data they had collected and found out that wails are only used at the beginning of songs and are dropped if the songs are sung following events that already attract conspecific attention (such as predator presence, alarm calls or fights). Then the research team conducted experiments on the physical propagation and the degradation of those sounds over distances and under different wind conditions.
“Finally, we field experimented with rock hyrax songs. We took a template song, played it, measured the responses by other rock hyraxes, and then we deleted most of the wail elements and replaced them with background noise. We also segmented wails and broke the continuous structure of the songs. With both of these manipulations, we saw a reduction in the audience’s responses”, explains the biologist.
Wails meet several criteria for an alerting component: They are stable over medium transmission distances, they happen at the start of the song, and they are associated with an increase in the response rate, which the researchers describe as a crucial benchmark for alerting significance. “Wails likely serve as alerting signals, even though they don't meet all of our criteria perfectly. Some ecological constraints definitely have an effect, such as habitat structure, background noises, or risks from predation. Besides, I would not go as far as saying that alerting is the only function wails have. They might encode additional information that we haven’t found yet”, Demartsev explains.
The researchers hope their framework for assessing potential alerting signals will be applied to other species as well. Future research could also examine the evolutionary trade-offs associated with producing highly detectable signals, e.g. enhanced conspicuousness to unintended receivers such as predators or competitors.
Key Facts:
- The study “Alerting components in animal vocalisation” was recently published in the journal Animal Behaviour.
- The study introduces a framework to test animal signals for their alerting function and, in a second step, applies this framework to evaluate whether the introductory notes in rock hyraxes’ songs meet the criteria for an alerting function.
- Authors:
Behavioural ecologist Vlad Demartsev (first author) works as a post-doc at the Cluster of Excellence "Centre for the Advanced Study of Collective Behaviour" at the University of Konstanz and is an associated researcher at the Max Planck Institute of Animal Behavior.
Behavioural ecologist Eli Geffen (last author) is professor at the School of Zoology at Tel Aviv University (Tel Aviv, Israel).
Other contributors to the paper were Yair Geva, Pablo Alba González and Amiyaal Ilany (all from the School of Zoology at Tel Aviv University) and Lee Koren (Bar-Ilan University, Ramat Gan, Israel). - Funding: Israel Science Foundation, Alexander von Humboldt-Stiftung, German Research Foundation (DFG) funding for the Cluster of Excellence "Collective Behaviour" (EXC 2117 – 422037984)
Note to editors:
You can download images here:
Photo (DSCN 1947 and/or 2780): Subtitle: Rock hyrax at Ein Gedi Nature Reserve, Israel;
Copyright: Héloïse Brotier and Lee Koren, Bar-Ilan University
https://www.uni-konstanz.de/fileadmin/pi/fileserver/2025_extra/wie_tiere_sich_untereinander_1.JPG
https://www.uni-konstanz.de/fileadmin/pi/fileserver/2025_extra/wie_tiere_sich_untereinander_2.JPG
Video (Sing 3.mp4): Subtitle: Rock hyraxes’ songs are quite complex and begin with wails.
https://youtu.be/dG1MrRnPkMM?si=4nTwfuLxE992S-z8
Copyright: Héloïse Brotier and Lee Koren, Bar-Ilan University
Journal
Animal Behaviour