A recent study conducted in the Cantabrian Mountains has revealed that brown bears are capable of deceiving their own kind, a behavior previously undocumented in the species. The research, which involved experts from the Spanish National Research Council (CSIC), FAPAS, various European and Spanish universities, and the Principality of Asturias, was recently published in the Journal of Mammalogy.
The findings suggest that a small minority of bears inhabiting the peaks of León, Asturias, and Cantabria may be intentionally misleading rivals regarding their true size. By leaving visual and chemical signals at heights unattainable for their actual physical stature, these bears appear to be attempting to deter larger, more dominant rivals to avoid direct confrontation. This strategy, the authors note, could reduce the costs of fighting and potentially increase reproductive opportunities for younger or non-dominant males. It is a strategy that recalls cases of deception described in other mammals, but which until now had never been documented in bears, according to researcher Vincenzo Penteriani of the National Museum of Natural Sciences.
The research team monitored 14 marking sites over a period spanning 2021 to 2024, analyzing 117,552 hours of video footage. Among the 164 bears tracked, seven males—representing 4.3% of the group—were observed engaging in this deceptive behavior. Of these seven, 57.1% were adults, while 42.9% were young bears. Researchers witnessed these individuals climbing trees or utilizing platforms to leave marks at heights exceeding two meters, which is the standard maximum reach for a bear standing on its hind legs. In one instance, a signal was recorded at three meters, with a broken branch nearby providing evidence that the animal had climbed to reach that height.
The authors of the paper state that these results suggest brown bears can manipulate index signals that were previously considered impossible to fake, adding complexity to their communication system. Even so, Penteriani and his colleagues remain cautious about labeling the species as naturally dishonest, given that the identified tricks are rare and occur in very specific parts of the areas studied. They emphasize that this work highlights a fascinating behavioral capacity in bears that justifies carrying out more observational and experimental studies.
Currently, the Cantabrian and Pyrenean populations of brown bears in Spain have recovered to over 400 individuals, a significant improvement since they were on the brink of extinction during the 1970s and 1980s. While they remain classified as endangered, conservation efforts have successfully moved them out of the critically endangered category.
