Perry S. Barboza University of Alaska, Fairbanks, USA Title Paying for sex: nutritional capital and income for arctic reindeer and caribou Abstract Caribou and reindeer must balance the demands for reproduction around the annual pattern of plant production. Males and females convert the income of food intake to the capital of body stores in summer. Consequently both sexes increase the size of the digestive tract and liver during summer. Small ruminal capacity and thin ruminal muscles indicate that lactating females cannot handle coarse forages as well as large males. Small females therefore require foods of higher quality than males and nonreproductive females. Males spend their capital at the start of winter by losing 23% of body protein and 78% of body fat over 77 days during rut. Rutting bulls decrease food intake and lose both ruminal and cecal mass. High concentrations of steroid hormones from the adrenals and the gonads are associated with changes in renal function and immune response. Reproduction increases mortality risks of males from disease and impaired homeostasis. Males also risk higher mortality in winter because they enter winter with less than 5% body fat. Females invest in reproduction throughout winter (pregnancy) and spring (lactation). All females reduce ad libitum food intakes from the winter solstice to the spring equinox before gradually regaining appetite. Consequently, both pregnant and nonpregnant females lose body fat through winter. Nonreproductive females quickly regain fat in spring when lactation prevents mothers from regaining body fat. Body protein is gained before fat in spring if females consume high N diets similar to emergent plants. Females conserve body protein on a low N diet similar to winter forages such as lichen. Reindeer birth near the nadir of N intake whereas caribou birth 28 days later after appetite restores N intake. Reindeer rely on body protein to produce 96% of fetal protein whereas caribou use 12% more dietary protein for their calf. Both reindeer and caribou rely equally heavily on body protein to produce milk. Environmental changes can alter the balance between income and capital for growing calves, rutting bulls and lactating females. Populations of caribou and reindeer will respond differently to changes in the environment depending upon the sex and age composition of the herd and the timing of reproduction. Management and conservation of this circumarctic species should consider the likely range of physiological responses in each herd to a given change in their habitat. CV 1991: Doctor of Philosophy, Department of Biochemistry, Microbiology and Nutrition, University of New England, Australia. 1984: Bachelor of Science (Biochemistry with Honors in Zoology), University of New South Wales, Australia. Professional experience 2002 - present: Tenured Associate Professor of Biology, University of Alaska, Fairbanks 1997 - 2002: Assistant Professor of Biology, University of Alaska, Fairbanks. 1994-1997: Visiting Assistant Professor, George Washington University, Department of Biological Sciences, Washington DC. 1993: Visiting Lecturer, Catholic University of America, Department of Biology, Washington DC. 1991 - 1993: Visiting Scientist / Comparative Nutritionist, Smithsonian Institution, Washington DC 1990: Smithsonian Institution Postdoctoral Research Fellow. Research interests Wildlife Physiology & Nutrition Selected recent publications Physiology of intermittent feeding: integrating responses of vertebrates to nutritional deficit and excess. P.S. Barboza and I.D. Hume. Physiological and Biochemical Zoology 79: 250-264. Ruminal fermentation and fill change with season in an arctic grazer: responses to hyperphagia and hypophagia in muskoxen (Ovibos moschatus). P.S. Barboza, T.C. Peltier and R.J. Forster. Physiological and Biochemical Zoology 79: 497-513. Body protein stores and isotopic indicators of N balance in female reindeer (Rangifer tarandus) during winter. Barboza, P.S. and K.L. Parker. Physiological and Biochemical Zoology 79: 628-644. Nutritional condition of Pacific Black Brant wintering at the extremes of their range. D.D. Mason, P.S. Barboza and D.H. Ward. Condor 108: 678-690. Institution address Perry S. Barboza University of Alaska Department of Biology & Wildlife, Institute of Arctic Biology PO Box 757000 Fairbanks AK 99775-7000 USA Telephone: 907-474-7142 office; Fax: 907-474-6967 ffpsb@uaf.edu http://mercury.bio.uaf.edu/~perry_barboza/