Humans are not the only mammals capable of deceiving their own child. That is the conclusion of this study focusing on brown bears in the Cantabrian Mountains, carried out with the collaboration of experts from CSIC, FAPAS, several Spanish and European universities and the Principality of Asturias.
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The paper published in the “Journal of Mammalogy” (source in Spanish) argues that a minority of bears spread across the peaks of León, Asturias and Cantabria may be ‘lying’ about their true size to avoid facing larger rivals. How? Through the signals and marks these mammals leave in their surroundings to stake out territory.
Seven times (4.3% of the 164 tracked) made markings unusually high by climbing or using tree trunks or other kinds of platforms to leave their trace at a height greater than their real size would allow. Of these, 57.1% were adults and 42.9% were young bears. “These results suggest that brown bears can manipulate index signals that were previously considered impossible to fake, which adds complexity to their communication system,” the authors sum up.
To investigate this behaviour, the team monitored 14 marking sites in the Cantabrian Mountains over 117,552 hours of footage between 2021 and 2024. The results showed that these cunning seven males climbed trees to leave chemical and visual signals higher than their actual height allows.
Brown bears usually leave their marks at the maximum height they reach when standing upright on their hind legs, around two meters high. However, the researchers observed a visual signal at three meters, a height unattainable for any animal standing on the ground. The discovery of a broken branch just below the mark suggests that the bear climbed up to make it.
“For a non-dominant male or a young individual, this strategy could provide advantages because, by appearing larger, they could deter bigger rivals, reducing the likelihood of a direct confrontationavoiding the costs it may entail and even increasing them reproductive opportunities. “It is a strategy that recalls cases of deception described in other mammals, but which until now had never been documented in bears,” says researcher Vincenzo Penteriani of the National Museum of Natural Sciences.
Even so, both he and his colleagues are cautious about branding ‘Ursus arctos’ a dishonest species as a rule, given that the ‘tricks’ identified are rare and occur in very specific parts of the areas studied. “Our work highlights a fascinating behavioral capacity in bears that justifies carrying out more observational and experimental studies,” Penteriani says.
Spain’s two brown bear populations, the Cantabrian and the Pyrenean, now number more than 400 animals after skirting extinction in the 1970s and 1980s. Although these bears remain endangered, they have left the critically endangered category thanks to the efforts of conservationists.