Garbage dumps are turning bears into couch potatoes. A survey of brown bears in north-east Turkey has revealed how visiting a dump has completely changed local bears’ lifestyles. Bears that visited the dump became more sedentary, no longer migrating and foraging over the same distance as those that didn’t.
“It’s surprising that two substantially distinct lifestyles can develop and coexist within a small and isolated subpopulation,” says Gabriele Cozzi of the University of Zurich in Switzerland. This is a first for brown bears, he says, although such differences have been found within groups of black bears.
Cozzi and his team radio-tagged 16 bears, then followed their movement for an average of 10 months, and up to 20 months. They found that the 10 “dump bears” – seven males and three females – did not stray far from the dump, except to hibernate during the winter.
By contrast, the six bears – three males and three females – that never visited the dump ventured far and wide. These bears migrated an average of 165 kilometres each year in search of food, especially in the period before hibernation, when they were probably “fattening up”.
The local authority in the city of Sarikamis is currently planning to close the dump. Cozzi’s survey was partly carried out to assess what the fate of the bears might be if this happened.
The best outcome, say the researchers, would be for the bears to revert to their previous forest existence. The other two possibilities are not so rosy: that the bears could die of malnutrition, or that they could instead forage in the city and its nearby villages.
“We anticipate that the situation could change, with bears venturing into the city should the dump close,” says Cozzi. “Bears may become too dangerous and be shot, and people may be injured.”
Recent incidents in Japan in which wild bears killed and ate parts of people suggest this scenario is far from fanciful. “Bear attacks on people are not unheard of around Sarikamis, and I’m aware of at least one case in 2013,” says Cozzi.
Back into the wild?
But Cozzi’s hope is that the bears can be “repatriated” into their natural habitat, a forest that there are plans to later link up with forests further north as an extended wildlife corridor. “The most important thing is to continue monitoring the bears to see how they react to the [dump’s] closure and the establishment of the wildlife corridor,” says Cozzi.
“This study reveals the complex consequences that human influence can have on a species that has adapted to human-altered landscapes,” says Andrea Flack of the Max Planck Institute for Ornithology in Radolfzell, Germany. “The brown bear has adjusted its habits and is now either showing this fascinating migratory behaviour or feeding on garbage dumps.”
Flack, whose own studies have focused on how contact with humans alters the migration habits of storks, warns that the bears’ reliance on the dump means that care must be taken about closing it.
“Although closing garbage dumps in the near future is most likely beneficial for the environment, we have to make sure that we don’t harm those species that came to rely on them,” she says.
Journal reference: Journal of Zoology, DOI: 10.1111/jzo.12365