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Conflicts often arise when large predators and free-ranging livestock share a common area. Various compensation schemes arc used to attempt solving these conflicts, but the costs of predation to suffering stakeholders arc often unknown. Semi-domesticated reindeer husbandry and large carnivores form one such system, where conflicts between predator conservation and the traditional livelihood are common. We apply an age- and sex-structured reindeer-lichen model to examine the effects of predation on reindeer management. Based on the previous studies we specify age- and sex-class-specific mortalities due to various predators, and study optimal reindeer husbandry under predation pressure and the costs of predation. We show that the costs of predation highly depend on the age-class-specific killing rates of reindeer by various predator species, but not on interest rate or pasture conditions. Regarding species that are more likely to kill adult reindeer in addition to calves, the total predation costs are clearly higher than the net slaughtering value of the predated animals. The decrease in steady-state yearly net income is highest for the gray wolf and lower for other predator species. Adapting to predation pressure includes increasing the size of the reindeer population in winter and changing the slaughtering age of males towards young adults, thus reducing the importance of calf harvesting. This result contrasts with the previous results from stage-structured models that do not fully include time lags related to long-living ungulate species. The costs of predation appear to be much higher in an ex post system than in a territorial compensation system, as in an cx post system herders have not adapted to the predation pressure and must search for the predated reindeer to gain compensations. Our results suggest that co-existence of a viable gray wolf population and profitable reindeer husbandry in the same area is not possible in most cases.

We apply an age- and sex-structured reindeer-lichen model to examine the role of winter pastures, pasture rotation, and supplementary feeding on economically optimal reindeer management. The model includes 17 age classes of females, 13 classes of males and a detailed description of winter energy resource utilization by the reindeer population. Reproduction is specified by a modified harmonic mean mating system and the diet choice between different winter energy resources follows the principles of the optimal foraging theory. Wintertime energy intake defines an individual's weight decrease and its consequences on mortality and reproduction. Lichen growth depends on habitat type and lichen biomass. The decision variables are the animals chosen for slaughter from each age and sex class and the amount of supplementary food given. Results show that the availability of arboreal lichens, the growth rate of ground lichens, and pasture rotation all determine the optimal solutions. Reindeer management aiming to maximize long-term net economic revenues leads to very low lichen densities if intensive feeding becomes optimal in the long-term steady state. Government subsidies promote reindeer herders to base management on supplementary feeding leading to lower pasture conditions and to the depletion of lichens.

This study presents an optimal harvesting model for the semi-domesticated reindeer (Rangifer t. tarandus) and its main winter energy source, ground lichens (Cladonia spp.). Females are divided into 17 age classes and males into 13. Reproduction is specified by a modified harmonic mean mating function and an age-specific reproduction success. Lichen availability determines individuals’ overwinter weight decrease, natural mortality, the number of calves per females and calves’ birth weight. The reindeer herding cooperative can choose the number of animals harvested from the 30 age/sex classes and is assumed to maximize the preset value of net income. The structured optimization model is solved as a fully dynamic system and for initial states that may not be close to the optimal steady state. This enables to study optimal recovery from overgrazed pastures and the optimality of the constant escapement policy. We show that given zero interest rate the optimal steady-state lichen density is less than 50% of the maximum sustainable yield level but nearly twice as high as empirically observed. Density dependence at optimal equilibrium is realized in calf weight and in the average number of calves per female. Optimal slaughtering is concentrated on six-month-old calves. Adult females are slaughtered at the age of 9.5 years and males at the age of 5.5 years. A moderate or high interest rate increases the steady state reindeer population but decreases pasture conditions. Dynamic solutions deviate from constant escapement, implying that the optimal recovery from initially overgrazed pastures is slower than suggested in existing studies and actual policy. The shadow value for males is three times higher than for females.