Behavioral development of a captive polar bear (Ursus maritimus) cub in the maternal den.

Two female polar bear (Ursus maritimus) cubs were born to mother Suka at the Detroit Zoo on November 17, 2020. One cub (Laerke) was hand-reared out of medical necessity, while the other cub (Astra) was mother-reared. Using audio-equipped video cameras previously installed in the maternal den, staff were able to conduct uninterrupted continuous monitoring on Suka and Astra for an unprecedented 12 weeks. Data collected during this time were analyzed descriptively. Astra spent a maximum of approximately 20% of any given 24 h period in nursing behaviors. Distribution of time spent nursing was relatively even across the 24 h day. In contrast to the limited data currently available, Astra spent only approximately 11% of the over 2000 h of behavioral data engaged in nursing behaviors. Astra left the nest for the first time in her fourth week of life, and time spent out of the nest gradually increased with age. Suka was observed guiding Astra back to the nest the first few times Astra ventured out. However, maintenance of maternal proximity did not appear to be a motivating factor in patterns of space use. The data presented here represent the longest uninterrupted continuous monitoring of a polar bear cub in the maternal den currently published. Publication of similar data from other institutions would establish more generalizable trends for early infancy development. These data are critical for understanding cub welfare and improving population sustainability and neonate mortality rates.