Black bears' day beds

Recently accepted in Wildlife Biology, is a paper examining den abandonment and the use of day beds during the transition into and out of hibernation by black bears on the island of Newfoundland.  Nathaniel D. Rayl, Todd K. Fuller, John F. Organ, John E. McDonald, Jr., Robert D. Otto, and Shane P. Mahoney are the authors of  “Den abandonment and transitional day bed use by black bears Ursus americanus in Newfoundland.”

Nathaniel Rayl says: “We noticed that a number of our collared bears weren’t staying in one place throughout the denning period.  Some movements occurred in the middle of winter, and we considered these classic cases of den abandonment, but most occurred at the start or end of the denning period, and it was less clear if we were documenting instances of den abandonment or simply the use of day beds for an extended period.  Other researchers have reported black and brown bears using day beds for days or even weeks at a time as they transition into or out of hibernation, but we couldn’t find anyone who had systematically described the use of these day beds.  We quantified the use of these day beds and investigated potential causes for den abandonment and departure from day beds in the fall.  Den abandonment is often induced by flooding, and we found that rainfall influenced day bed departure in the fall, and that some bears used the same sites as day beds and dens in different years, highlighting the difficulty researchers may have in distinguishing between day beds and dens.  Den abandonment has been used as an indicator of anthropogenic disturbance, but we were unable to find a relationship between environmental or anthropogenic disturbance and den abandonment events.  Because our research was conducted in a relatively remote ecosystem, our results may serve as baseline information about den abandonment.”

Photos: Nathaniel Rayl and Steve Gullage

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