Document Type

Grand Teton National Park Report

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Black bears have delayed implantation with fetal development and lactation energy demands during a period of maternal hibernation and starvation. Pregnant females in a state of diapause had about 23% greater fat depots than non­reproductive females going into hibernation. Fat provided 92% of the total energy for lactation and gestation. Rates of fat loss were 27% and protein loss 58% higher for reproductive females compared to non-reproductive females. The cost of winter reproduction to include gestation and lactation was 1432 kj/day to produce two cubs. While reproduction required elevated protein breakdown, the overall loss was relatively small, perhaps due to a short gestation period and urea recycling.