Monday, November 15, 2010

Giant Stuffed Teddy Bear and Why Bears Rub Trees

The giant stuffed teddy bear means different things to different people. For some it's a best friend, there to cry on when things get tough. For others it's a playmate that shares both great and small adventures. One thing is certain, however: a giant stuffed teddy bear is the perfect companion for anyone lucky enough to have one.

There have been many theories as to why bears rub trees. Some have thought that female bears do it when they are ready to mate. Others have been of the mind that bears simply rub trees to give themselves a good scratch so as to get rid of parasites. Or, it could be that they do it so sap from the tree will rub off on their fur thus acting as an insect repellent. It's been very tough to test out these theories given bears live at such low densities and the rubbing behavior is quite a rare occurrence.

Over a two year period, Dr. Owen Nevin of the University of Cumbria, used four digital cameras containing infra-red strips to collect rubbing tree data on grizzly bears in British Columbia. Since he had already spent more than a decade logging rub trees already, he was able to set up the cameras opposite those same trees to see which bears were doing the rubbing and when. Along with the use of satellite telemetry equipment, Nevin was also able to track an individual bears' movement.

Nevin said "the cameras show that adult male bears are the most likely to rub trees, and the satellite telemetry tells us that males move from valley to valley in large loops, marking trees as they go, while looking for breeding females." Nevin is of the belief that adult male bears are marking trees so as to get to know each other better. In addition, he thinks by marking a familiar scent on a tree, it could go a long way to reducing the fighting that goes on between adult males. Given males bears can both injure significantly and/or kill each other, when one male smells the scent marks left on a tree by another male, it's a message that he is in another's territory thus it's better to back away so a fight doesn't ensue.

Males bears are known for sometimes killing a female's cubs so as to free up an opportunity to mate with her. Through Nevin's study, it suggests the possibility that young bears rub trees so as to fool males into not killing them. With the cameras that were set up to catch bears rubbing trees, cubs were caught on them being chased away from their mother by large males. Those same cubs went back to the tree the male had marked and rubbed up against themselves - two or three times. By doing this, it made the cubs smell like the big male, which in turn made the male bear believe he was smelling a relative; the likelihood of aggression towards a relative is less prevalent.

A giant stuffed teddy bear has no desire whatsoever to rub up against a tree. The fact that it may never even come into contact with a tree in its lifetime, gives it even less of a need to want to do so. A giant stuffed teddy bear has but one concern in its life: ensuring it's the very best companion its owner will ever have.

Copyright Shelley Vassall, 2010.

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