Denning characteristics and movement patterns of female polar bears with cubs in Svalbard during the first month after emergence : implication for detecting denning locations

摘要

Satellite telemetry records of temperature, activity and position data for female polar bears (Ursus maritimus) known to have been (n=11) and to not have been (n=15) in maternity dens during winter were analyzed during the period from December 15th to March 1st for patterns that could be used to demonstrate denning in other female bears by means of telemetry collars. Temperature was found to be the best indicator, and sufficient alone to indicate denning, due to above freezing values within the dens throughout the winter while outside temperatures varied and were mostly below freezing. Using this signature, 34 individual females (n=64 bear-winters) out of 207 collared females (n=290 bear-winters) were with high certainty established as denning bears. Telemetry data for selected and known animals was analyzed for the period from September 1st to May 31st. Mean entry and breakout dates (entry – Nov.11, exit – March 28) and a mean length of denning ( 147 days) were estimated for known and selected bears. Further, females’ movement was analyzed with regard to distance from the dens during the first few weeks after emergence. Distances were estimated starting from the first corresponding negative temperature transmission, taken as a break out date and for 30 days forward. Median distance of 19.7 km from the den was recorded for the day 6th after emergence and 95.5 km after 30 days. By April 20th, 33.3% of females were within 38.5 km from the den. Therefore, it appears that after emergence females spend less than one week in the denning area. However, large variability in travelled distances was present (from 0.3 km to 247 within the first week), likely demonstrating either loss of cubs or habitat selection (island vs. pelagic). Upon analysis of denning locations, 66 dens were plotted and 5 appeared to be on sea ice.Key words: Ursus maritimus, polar bear, Svalbard, Spitsbergen, satellite telemetry, reproduction, spatial use.