ABSTRACT
In the wild, female polar bears (Ursus maritimus) with cubs may spend extended periods of time within the den following initial emergence. As a result, studying behavioral development of cubs at the denning site has been difficult and unreliable. Although care staff at zoological institutions have easier access to animals, every effort is made to minimize intrusions to maternal groups, which presents research limitations. Detroit Zoological Society staff used audio-equipped cameras installed in behind-the-scenes spaces to conduct approximately 9 weeks of monitoring on two female polar bear cubs of the same litter, one of whom (Laerke) was hand-reared while the other (Astra) was mother-reared. Monitoring spanned ages 14-24 weeks and consisted of 12, 5-min focal observations per observation day timed to evenly cover the entire 24-h day. Using generalized linear mixed models, we examined relationships between behavior and time of day, hour, and age. We also conducted descriptive analyses and used these to draw comparisons between the two cubs where appropriate. Despite different rearing environments, both cubs had highly comparable patterns of inactive, locomotory, and independent play behaviors. Astra generally decreased time spent nursing and in proximity to Suka as she aged. Data presented here represent a continuation of previous neonatal observations conducted on Astra, adding to the minimal body of knowledge currently available on first year polar bear cub development. We also report successful mitigation of stereotypic behavior in Laerke. Further studies of captive maternal groups can provide insight into this critical developmental stage, supporting both captive-based breeding efforts and in situ conservation efforts.
Subject(s)
Ursidae , Humans , Female , Animals , Animals, Zoo , Stereotyped BehaviorABSTRACT
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.
