Behavioral and Physiological Development of Polar Bear Cubs
Polar bear (Ursus maritimus) cubs are born blind, deaf, hairless and weighing less than one pound. Although there is no way to observe the behavior of denned mothers and cubs in the wild, the Detroit Zoo has equipped denning spaces with audio and infrared cameras to learn more about this crucial developmental period. On November 17, 2020, adult female Suka gave birth to two cubs at the Detroit Zoo. One cub (Laerke) was hand-reared out of medical necessity, while the other cub (Astra) remained with Suka to be mother-reared. The extraordinary dedication of animal care staff allowed for continuous 24-hour monitoring of Suka and Astra throughout Astra’s first 12 weeks of life. This comprehensive and unprecedented monitoring allowed us to track Astra’s patterns of nursing, rest and increasing independence during the critical neonate phase. We were able to continue this developmental monitoring with both Astra and Laerke after Laerke had been medically stabilized. Between the ages of 14 and 24 weeks, we conducted additional observations to examine shifts in rest, locomotor and independent play behaviors. Despite their differences in rearing environments, Astra and Laerke demonstrated remarkably comparable daily and hourly patterns of behavior. These data were promising for Laerke’s growth trajectory as a healthy, independent, young polar bear. In 2021, the Detroit Zoo took in an orphaned grizzly bear (Ursus arctos horribilis) cub, Jeb, as a social partner for Laerke. This provided a whole new opportunity to study this unique social pairing and contrast these three young bears with each other. We took the opportunity to monitor their physiological development through analysis of fecal glucocorticoid metabolites (FGMs). We were able to examine the relationship between their individual FGM patterns and age, environmental factors and their social housing conditions. By analyzing almost 800 fecal samples and over 100 hours of behavioral data, we found that Astra and Laerke displayed highly similar physiological profiles, but both significantly differed from Jeb. We were able to use these data to glean novel insights into the physiological states of juvenile bears during key developmental periods. We continue to process a wealth of data we collected on the polar bear cubs throughout their residence at the Detroit Zoo, and we look forward to sharing it with the community in pursuit of excellent welfare.
https://doi.org/10.1002/zoo.21757