Spanish brown bears caught faking their size to look tougher than rivals

Some crafty brown bears in northern Spain have been rumbled for pulling a fast one on their rivals. Scientists have filmed the animals deliberately leaving marks higher up trees so they seem bigger and more intimidating than they really are.

Researchers from the Museo Nacional de Ciencias Naturales (MNCN-CSIC) spent four years watching 164 brown bears in the Cantabrian mountains. They collected a massive 117,000 hours of camera-trap footage across 14 popular marking spots between 2021 and 2024. Results, published in the Journal of Mammalogy, show seven of those bears, roughly one in twenty, worked out how to cheat the system.

Bears normally leave scratch marks and scent signals at the highest point they can reach while standing on their back legs, around two metres off the ground. That height usually gives a fair idea of an animal’s real size and strength. However, a handful of crafty males decided that wasn’t enough. They climbed trees or used natural platforms to push their marks higher, sometimes as far as three metres up. One broken branch found right under an especially high mark gave the game away, clear proof the bear had scrambled up to leave it.

First time this cunning has been filmed in bears

Lead researcher Vincenzo Penteriani from the MNCN said the discovery was a real eye-opener. “Although this is exceptional behaviour, it is the first time it has been documented in bears, which shows their communication is more complex than we thought.”

To test the idea properly, the team fixed wooden platforms next to the usual marking trees and posts. Sure enough, some bears hopped onto them to leave their calling cards higher than nature intended. Scientists believe the tactic could help younger or less dominant males put off bigger rivals without a proper fight. It might even improve their chances with the females during the mating season.

Penteriani summed it up neatly: the bears’ communication sits in a constant balancing act, not completely honest, not completely dishonest, but always shifting between the ones sending the signals and the ones reading them. For a species once thought to stick to straight-up messages about size and power, these Cantabrian brown bears have shown they can be a bit more slippery than anyone expected. It’s so far unclear if Spanish bear cubs boast to their friends that their dad’s bigger.