There are many reasons why bears scratch their backs on tree trunks, and scientists have added one more to the list.

Sometimes they do this because, through the smells they leave on the trunks, they communicate with other people in the community. In other cases, they are trying to remove their hair, while others are trying to relieve an itch that they cannot reach with their paws.

Now, new research suggests that bears may be rubbing their trunks to coat their fur with a natural tick repellant.

When the bears scratch the trunk, the wood releases resin and other saps. These substances stick to their fur and skin, making them not only “waterproof” but also more “repellent” to tick bites.

As Agnieszka Sergiel, a bear biologist at the Polish Academy of Sciences and lead author of a study published last month in the Journal of Zoology, explains, animals rarely engage in complex behaviors, such as rubbing against trees, for one reason only.

“We see a number of examples among mammals that use self-healing,” she notes, who, along with her colleagues, decided to study whether this habit of bears protects them from parasites.

Experiment

Over time, biologists have noticed that brown and black bears have a preference for certain types of trees, especially conifers. They are also attracted to beech resin, which is a useful experimental substitute for substances released from trees. The resin’s effect is so strong that scientists use its strong, sticky smell to attract bears for research or to lure them into their zoo habitat.

To test the correctness of this hypothesis that beech resin is a tick repellant, Dr. Sergel observed the behavior of Dermacentor reticulatus trapped in a tube, a common type of tick that attaches to bears. In the dilemma of tar or clean water, ticks ran to the latter.

The researchers also tested other material that attracts bears, turpentineand they found the ticks hated him too.

The simple conclusion that beech tar is not at all popular with mites is the first experimental evidence to support the widely held belief that tar can also act as an insect repellant, the scientists say.

The researchers did a “nice, clean experiment that gave them clear evidence” that the mites avoid beech tar, notes Andrea Morehouse, a freelance biologist in Alberta who specializes in bear-human interactions but was not involved in the recent study. research. “Pest repellent is probably not the primary function of wiping trees, but it certainly is an added benefit,” he adds.

Bears aren’t the only animals in the wild that use natural insect repellants. monkey capuchins, for example, diligently rub their fur against citrus fruits, Dolphins it is believed that they treat their skin with corals, and cats they can use catnip as a mosquito repellant.

Source: New York Times.