Sex-, age-, and time-specific visual communication in brown bears

Abstract

Intraspecific communication in mammals is well-documented but generally restricted to chemical and acoustic signaling. However, other overlooked channels, such as visual signaling, may be used to communicate among conspecifics. Here, by using experimental manipulations together with camera traps on 13 brown bear (Ursus arctos) rubbing trees in the Cantabrian Mountains (northwestern Spain), we document detailed temporal patterns and behavioral aspects of a recently discovered novel communication channel for this species, visual signaling through the trunk debarking of focal trees. Video footage showed that visual marking is a sex-, age-, and time-specific means of communication in brown bears, being performed exclusively by adult males during the mating season (mainly April–June in the study area). Trunk debarking was always associated with chemical marking and was never an isolated behavior, suggesting that visual and chemical signals might be complementary. Visual and chemical marks may provide different information; for example, visual marks could be an indicator of individual size and, thus, the dominance status of adult males looking for mating opportunities. This is the first time that evidence is provided showing that visual signaling in a large carnivore is exclusive to a specific class of individuals (adult males) and linked to reproductive needs only. Bear visual signaling not only represents an advance in our comprehension of animal communication but may also serve to easily locate the mating areas of mammals, which are crucial for large carnivore species, such as the brown bear, that frequently need specific and urgent plans for conservation and management.

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“…and several other carnivore and ungulate species investigate bear smell on rubbing trees (Penteriani et al, 2023). Our results can thus guide the protection of panda habitats more precisely.…”

“…They might have also chosen these trails, which are often visited by other animals, as a way of indicating their presence to the other species. For instance, brown bears ( Ursus arctos ) and several other carnivore and ungulate species investigate bear smell on rubbing trees (Penteriani et al, 2023 ). Our results can thus guide the protection of panda habitats more precisely.…”

“…Scratch marks were accompanied with AGS marks; thus, scratch marks alone do not convey information. However, scratch marks cannot be considered a byproduct of chemical marking and their exact implications need to be further explored (Penteriani et al, 2023 ). Interestingly, some marked trees had only bite marks, and these marked trees were more numerous than those with only urine marks, which was not found in previous studies.…”