What we know and what we don’t know about bear communication

Animal communication is a fascinating and extremely complex topic, since species can use several forms of communication to convey different information to their relatives. Although the study of animal communication has been and remains one of the most fruitful areas of research, much remains to be discovered.

In the case of communication in terrestrial mammal species, much of the research has focused on communication via chemical signals (feces, urine, and body glands) and acoustic signals (such as howling). However, other forms of communication, such as the use of visual cues, have been overlooked, which may be just as important.

In fact, there are several reasons to believe that visual communication in mammals may be used more frequently than previously thought.

constant visual cues

The first reason has evolutionary roots. The coloration of mammals has become a signal for intra- and interspecific communication.

In addition, visual signaling through physical marks such as bites and scratches is permanent and thus has the advantage of being durable. Environmental factors such as rain or snow are less likely to affect their detectability compared to transmission via chemical signals.

Thus, the temporal persistence of visual cues may allow people to reduce repeat visits to these strategic marking points. This leaves them with more time for other activities such as foraging and breeding.

For solitary species that typically reach low population densities, such as brown bears (Ursus Arktos), whose direct interactions between people are infrequent, it can be very important to develop communication channels that can communicate on an ongoing basis about their personality, age, gender and location.

Chemical tongue of bears

To date, studies of bear communication have identified chemical signals as the primary form of communication.

Ursids mainly use three forms of olfactory communication:

• Rubbing various parts of the body against tree trunks located at strategic points in their vital zone.

• When urinating and depositing secretions from the urogenital glands.

• Leaving an aromatic trail on the ground with the help of glands located on the soles of the feet.

But since the early 1980s, some researchers have been curious about the tracks that brown bears leave on trees.

The function of biting and scratching the bark of trees has given rise to several hypotheses, mainly related to the deposition of odor by glands (i.e., chemical signaling). However, these ideas have never been attempted to be demonstrated experimentally.

Thus, these visual markings provided a unique but unexplored opportunity to explore new possible forms of visual communication in terrestrial mammals.

marks on trees

A group of researchers, also intrigued by these bright markings that bears leave on trees, decided to conduct a series of experimental studies to test the idea that, in addition to chemical communication, brown bears can also use visual cues for intraspecific communication.

To test our initial hypothesis, we concealed bear tracks on trees in the Cantabrian Mountains with pieces of bark from the same species of tagged tree, and recorded the behavior of the bears as they passed through these trees using camera traps. .

Thus, we found that these visual markings were characteristic of adult males during the rutting season (mainly from April to June in the study area) and that they were always associated with the friction of the body on the trunks (and sometimes with the footprint left) on the floor). This behavior suggests that visual and chemical cues can complement each other.

In fact, they may provide different information. Visual markings will serve as an indicator of individual size and therefore dominance status of adult males seeking mating opportunities.

New ideas that open the way

In addition to being able to learn about the ways in which charismatic and inaccessible species like the brown bear communicate, we had the opportunity to learn a great lesson. It is about the importance of distancing ourselves from well-established ideas and using our imagination to discover new paths based on scientific evidence.

The main goal of ecology is to try to explain the many and different models of biological systems, as well as the behavior of species. Achieving this goal is not easy, especially given the impressive diversity and richness that characterizes the natural world.

In this scenario, the greater the variety of biological models on which we are based, the closer we come to understanding the rules that govern systems, leaving aside an ecology oppressed by the needs imposed by productivity, where we limit ourselves to the study of biological models that are most easily provided by fast and easily published results.

If we lose this freedom, we also lose important information needed to understand the vast diversity and complexity of the patterns observed in nature, the strategies used, complex structures, pathways, and evolutionary intersections.

The physicist Freeman Dyson, speaking of the paths traveled by geographical exploration, said that in the beginning, when everything had to be discovered, great goals were the only goal of explorers. For George Everest, reaching the top of the mountain that would later bear his name was his only goal, and everything that stood between him and Everest, rivers, jungles and plains, were only obstacles.

In the same way, ecology, by its origin and lack of knowledge, must have had great goals, and these goals were the basic regularities, universal laws underlying the functioning of ecosystems and species.

Now in many cases we are talking about details, sometimes small, but important. Everything that might have seemed marginal or uninteresting before, these rivers or these barely explored jungles, now still retains its richness and interest. And it is these seemingly secondary, but unknown ways that we have to look for.

Vincenzo Penteriani, Researcher at the National Museum of Natural Sciences (MNCN-CSIC) and María del Mar Delgado Sánchez, Researcher at the Mixed Institute for Biodiversity Research (University of Oviedo – CSIC)

This article was originally published on The Conversation. Read the original.

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