Discoveries

February 10, 2023

A Tree’s Bounty

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A new study found that bears employ a natural insect-repellent to prevent ticks from feasting on them, the New York Times reported.

Bear biologist Agnieszka Sergiel observed that the large predators have a tendency to rub their fur on tree bark for a variety of reasons, including marking scent and scratching an itch.

She noted that this shimmying leads to tree resin and sap leaking out of the trees and sticking to the animal’s fur. These substances are water-resistant and attach to fur and skin, making them a great contender as an efficient tick repellant.

Sergiel and her team tested this theory by monitoring how ticks reacted to beech tar, a sticky material that attracts bears and serves as a proxy for substances leaked by trees.

In their study, they placed Dermacentor reticulatus ticks – known to feed on bears – in horizontal tubes and observed whether the insects would approach the side with beech tar or the one with distilled water.

All ticks would move as far as possible from the tar and hide under the water.

“It was really obvious they hated the beech tar,” said co-author Agnes Blaise.

The team saw that ticks had the same reaction when turpentine, which also attracts bears, was used.

The findings provide the first experimental evidence supporting the longstanding idea that tree resins can act as a bug repellent.

The researchers hope that further studies, including on wild bears and ticks, can help in better understanding these natural repellents.

This story originally appeared in the February 10, 2023 newsletter, Lights Out.