Reproduction in female reindeer and caribou.

Reindeer and caribou which are polyestrous, undergo estrous cycles of two lengths, a short cycle of 10 to 12 days, and a long cycle of 24 days. The duration of pregnancy in free-roaming animals was found to be considerably longer than in animals reared in captivity, which may be due to prenatal undernourishment. The estimated digestible energy consumed during the late pregnancy of penned animals amounted to about 6000 kcal/day.