2008 Alaska Park Science Symposium
October 14, 2008
Timing of Birth and the Allocation of Body Protein to Calves in Arctic Caribou and Reindeer
Perry S. Barboza1
1Inst. Arctic Biology, Dept. Biology and Wildlife, University of Alaska Fairbanks, PO Box 757000, Fairbanks, AK, 99775-7000, USA, Phone 907-474-7142, Fax 907-474-6967, ffpsb@uaf.edu
Reindeer (Rangifer tarandus tarandus) and caribou (R.t. granti) use body stores (capital) and food intake (income) for survival and reproduction. Intakes of low-nitrogen (N) food declined in winter and increased in spring (51 to 83 g DM•kg-0.75•d-1). Reindeer calved before regaining food intake whereas caribou calved 28 days later. Body N was conserved by minimizing oxidization of amino acid N to urea. Maternal protein stored from early winter was used for 96% of fetal growth in reindeer but only 84% of fetal growth in later-birthing caribou. Both subspecies rely on maternal body protein for 91% of the protein deposited in the neonate via milk over the first 4 weeks. All females lost body protein over winter, but lactating females continued to lose protein while nonreproductive females regained protein. Net costs of lactation above maintenance were greater for N (110-130%) than for energy (40-59%). Large fat stores in reindeer spare body protein from oxidation in winter, whereas less fat with the same body protein favors migration in caribou when food is inadequate. The resilience of Rangifer populations to variable patterns of food supply and metabolic demand may be related to their ability to alter the timing and allocation of body protein to reproduction.
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