Reproductive Biology of Captive Polar Bears

January 1, 2001
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Observations on the breeding activity of captive polar bears (Ursus maritimus) at the St. Petersburg Zoo were collected by 2 technicians and other zoo employees. Between 1932 and 1988, data on 50 litters and 88 cubs were recorded. Most copulations (70%) occurred during March-April and were independent of weather conditions and ambient temperature. Coitus lasted from 10 to 40 minutes (n = 18). Mean duration of pregnancy was 224 days (range = 164-294 days). Duration of pregnancy was mainly influenced by the date of copulation, because there was little variation in timing of parturition. Mean litter size was 1.8 cubs (n = 50 litters). Most litters were composed of one 1 or 2 cubs; there were 2 sets of triplets. The sex ratio at birth was close to 1:1, with slightly more males (52.3%; 46 males and 42 females).

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