Animals in nature must forage for food to help pay their energy debts. When their current energy bills are paid, excess energy can be stored internally as body fat, or externally as a food hoard. Little is known about the distribution of energy among these alternatives and less is known about energy distribution with the addition of other energy consumers - offspring - whether as fetuses during pregnancy, or as young during lactation. The first goal is to determine the energy distribution strategies during the energetically demanding conditions of pregnancy or lactation. A second goal is to determine if a proposed signal of body fat stores, leptin, affects energy distribution strategies. This will accomplished using a species that naturally hoards food, Siberian hamsters. Foraging effort will be controlled by varying the required number of running wheel revolutions to earn food pellets from outside a semi-natural burrow. We will measure the amount of food foraged, eaten, hoarded, stored as fat, and deposit in their offspring during pregnancy, lactation, or with leptin treatment. Collectively, these results should help define the energy budget strategies of animals raising their young. This is a fundamental problem in the regulatory biology of all species.
