Expert: Jonathan Wright - 6/13/2005

Question
Do bears put a plug of moss up their backsides before they hibernate to stop ants or other small creatures going up there?

Answer
Dear Cath

Thanks for your question. I have looked up various websites and, while they contain some conflicting information, there is no confirmation that “bears put a plug of moss up their backsides” before hibernating.

http://216.239.59.104/search?q=cache:wihD2z9MQ0MJ:www.tpwd.state.tx.us/publicati... states that just before the bear beds down, it usually eats a laxative-type food to clean out its intestines. It then eats a last meal of tough, fibrous roots that form an intestinal plug or tappen that remains in place until spring. The tappen may also be composed of pine needles mixed with hair licked from the bear's coat. The stomach then contracts into a tight, hard knot to prevent any further intake of food, and the bear is ready to sleep.

http://www.nps.gov/yell/nature/animals/bear/infopaper/info10.html and http://www.madsci.org/posts/archives/may97/859503366.Zo.r.html state that bears were thought to eat roughage prior to den entrance. This would scour their digestive tract and form a plug in the anus to prevent them from eating any more food that fall. Instead, the plug  or ‘tappen' is made up of faeces, dead intestinal cells, hair, and bedding material. It forms during hibernation and not before. As bears do not eat during the winter hibernation period, there is little build up of nitrogenous wastes, so they do not urinate or defeecate. They produce some faeces, but the plug may keep the bear from defecating inside the den during hibernation as faecal plugs are found just inside or outside the dens of bears that have just emerged.

http://www.ansible.co.uk/Ansible/a13.html states that a 'tappen' was a mucous plug, which forms in the rectum of a polar bear during hibernation and closes it.

http://www2.cddc.vt.edu/gutenberg/etext05/8032410h.htm#13 says that some authorities believe that, as bears develop fat reserves in autumn, the fat produces carbon, which induces sleepiness. As the stomach becomes empty, it shrivels or draws into a very small space. It is rendered totally useless by a substance called 'tappen' that clogs it and the intestines. The tappen is formed of pine leaves and other material that the animal takes from ants' nest and the trunks of trees in its search after honey. During hibernation, the bear seems to live on its fat, while the tappen prevents its too rapid consumption.

In summary, the tappen forms inside the body and plugs the anus during hibernation. A bear does not place moss up its backside, nor does it place a rock there, which was one of my earlier questions. The tappen prevents faecal material leaking out of the bear's body and soiling its home during hibernation. Apart from hygiene, the smell of faces could attract enemies during a vulnerable period for the bear. The tappen is not produced to stop small animals going up the bear's backside, but its presence helps to prevent it. Whether ants would naturally want to go up a bear's backside is another question!

I hope this helps.

All the best

Jonathan