Odorant source used in Eurasian beaver territory marking

Mammals use urine, feces, or the secretion of specialized skin glands to mark their territories. These sources can carry different information and, thus, have different functions. Presently it is not known if beavers (Castor spp.) deposit castoreum (primarily a mixture of secondary metabolites from urine) from the castor sacs and secretion from the anal glands (AGS) together or alone when scent marking their territories. We hypothesized that castoreum would be the main scent signal used in the defense of beaver territories during winter and predicted that castoreum would be deposited more often than AGS. A total of 96 scent marks on snow were collected from January 1 to March 31, 1997-1999 in the Bø River, Telemark County, Norway. In order to obtain control material, we chemically analyzed AGS and castoreum from 60 dead beavers collected during January-May 1997-1999. We compared the compounds found in the dead beavers with compounds found in the scent marks on snow. Samples were analyzed by using gas chromatography-mass spectrometry (GC-MS). All 96 scent marks contained compounds from castoreum, whereas compounds from AGS were found in only four scent marks. This suggests that beavers do not specifically deposit AGS on scent mounds as they do with castoreum and that the AGS compounds we found probably were remnants of AGS from the feet or fur following pelt lubrication or coprophagy behavior. We conclude that castoreum is the main scent signal used in the defense of beaver territories during winter.