BREEDING PAUSES IN ARCTIC RANGIFER: POTENTIAL PROGENITORS Robert G White, Colin J Daniel, Don E Russell, Ray D Cameron (Res & Grad Studies, UAA, Anchorage; Apex Res Mgmt Sol, Ottawa; Yukon College, Whitehorse, Institute Arctic Biology, UAF) ASSUMPTION: A breeding pause (BP) is common in Arctic Rangifer 1 HYPOTHESIS: The BP is life-history response to seasonal protein limitation PREDICTION: A major progenitor of the BP is the “selfish cow” syndrome 2,3 that serves to minimize maternal mortality and optimize reproduction APPROACH: Use an energetics/protein model 4 : simulate effects of a set of variables (V x ) determine their consequences on: fecundity, birth weight, five (5) weaning outcomes [extended lactation] 5 subsequent BP determine influence of selfish cow 1, Cameron 1994 J Mamm 75:10-13; 2, Russell et al 1996 Rangifer S I 9: ; 3, Russell et al 2005 CWS Tech Rep Ser pp; 4, Therrien et al 2007 Beha Ecol Soc 62: ; 5, Gerhart et al 1997 J Zool 142:17-30 Base 3 calves non selfishBase selfish Breeding pause Breeding pause Breeding pause NP P 60 kg Extended lactation Simulations using winter conditions that result in 0 BW gain does not allow repeated reproduction and weaning. Mortality inferred as 0 FAT reserves in April of 2 nd gestation. “Selfish cow” conserves PTN but results in lower weaning weight. Nutrition is the inferred progenitor. Next steps: 1.Simulate effects of breeding pause on calf life history pattern (age of first reproduction, FIG. 1). 2. Influence of agents that synchronize pauses and that will affect populations (FIG 1). 3. Simulate influence of winter diet on N recycling and on PTN dynamics. FIG 1. Fig 1. Time series of pregnancy and pauses of cow and offspring (P=pregnant; E=barren) years Figure 2, Output from 2 model runs Calf weight Cow weight Cow Protein weight Cow fat weight Calf weightCow weight Cow Protein weight Cow fat weight

Base 3 calves non selfishBase selfish Breeding pause NP P 60 kg

Base 3 calves non selfish Base selfish Breeding pause NP P 60 kg