Bears May Rub Against Trees for Protection From Parasites


There are a lot of causes bears shimmy and scratch towards timber. Typically they impart by scent-marking timber, different occasions they’re eradicating hair and scratching that hard-to-reach itch. A brand new examine posits a further perk: slathering on nature-made tick repellent.

When bears wriggle towards bark, the tree scratching posts leak out tars, resins and saps. The thick tar of beech timber sticks to fur and pores and skin the longest, and it’s waterproof, making it a powerful contender for an efficient tick repellent.

Agnieszka Sergiel, a bear biologist on the Polish Academy of Sciences and an writer of the examine printed final month within the Journal of Zoology, stated animals seldom interact in advanced behaviors resembling rubbing towards timber for a single motive.

“We see loads of examples amongst mammals utilizing self-medication,” she stated. So, she and her colleagues determined to review whether or not rubbing towards timber may shield bears towards parasites.

For years, biologists have noticed that brown and black bears have an affinity for sure varieties of timber — particularly beech timber. The timber’ attraction is so sturdy that scientists use the sticky, sturdy scents of beech tar to draw bears for research or to name them inside in zoos.

To check the speculation that beech tar is a tick repellent, Dr. Sergiel discovered herself looking at tube after tube of tar and trapped Dermacentor reticulatus, a widespread arduous tick identified to feast on bears. She watched to see if the ticks would run away from beech tar on one aspect and towards secure, plain water on the different finish of the tube.

And run they did!

“It was actually apparent they hated the beech tar,” stated Agnes Blaise, a biologist on the College of Strasbourg in France and an writer of the examine. “Some had been actually speedy, working round and hiding beneath the water.”

The researchers additionally examined turpentine, a bear attractor, and the ticks despised it as properly.

The one ticks that didn’t depend, Dr. Sergiel added, had been those that managed to flee the tube solely.

“There have been some Houdinis,” she stated, “however they had been good lab animals.”

The researchers centered on ticks for his or her examine as a result of they’re geographically widespread and environmentally versatile — and due to local weather change, spreading farther and remaining energetic longer. Ticks are additionally illness vectors, though scientists are nonetheless studying about what pathogens they unfold to bears.

The straightforward results of beech tar not being well-liked with ticks supplies the primary experimental proof supporting the longstanding concept that tree resins may act as a bug repellent.

The researchers “had a pleasant, tidy experiment that offered some fairly clear proof” that ticks had been avoiding beech tar, stated Andrea Morehouse, an unbiased wildlife biologist in Alberta whose work focuses on bear-human interactions and was not concerned within the examine. “Repelling parasites might be not the first operate of tree rubbing, nevertheless it definitely could possibly be a further profit.”

Hannah Tiffin, an entomologist whose graduate analysis at Penn State College centered on ticks and bears, hadn’t heard of the concept of tree tar as insect repellent.

“I believe it’s a extremely fascinating path to go and will make sense,” she stated.

Different animals within the wild use nature-provided bug repellents; for instance, Capuchin monkeys studiously rub their fur with citrus and dolphins might deal with their pores and skin with coral. Your cat might even use catnip as a mosquito repellent. So it’s completely believable that bears may accomplish that, too, stated Dr. Tiffin, who was not concerned within the examine and is now a postdoctoral researcher on the U.S. Division of Agriculture.

There’s nonetheless loads to be discovered about tar as a tick repellent, Dr. Sergiel famous. Constructing out the scarce information of parasites discovered on bears within the wild (together with ticks) might be some of the necessary steps to furthering this work, the researchers stated. Amassing fur and resin samples from bears and testing parasites’ responses to these supplies is also helpful, Dr. Tiffin added.


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