Abstract
Reindeer herding in Sweden is a form of pastoralism practised by the indigenous Sámi population. The economy is mainly based on meat production. Herd size is generally regulated by harvest in order not to overuse grazing ranges and keep a productive herd. Nonetheless, herd growth and room for harvest is currently small in many areas. Negative herd growth and low harvest rate were observed in one of two herds in a reindeer herding community in Central Sweden. The herds (A and B) used the same ranges from April until the autumn gathering in October–December, but were separated on different ranges over winter. Analyses of capture-recapture for 723 adult female reindeer over five years (2007–2012) revealed high annual losses (7.1% and 18.4%, for herd A and B respectively). A continuing decline in the total reindeer number in herd B demonstrated an inability to maintain the herd size in spite of a very small harvest. An estimated breakpoint for when herd size cannot be kept stable confirmed that the observed female mortality rate in herd B represented a state of herd collapse. Lower calving success in herd B compared to A indicated differences in winter foraging conditions. However, we found only minor differences in animal body condition between the herds in autumn. We found no evidence that a lower autumn body mass generally increased the risk for a female of dying from one autumn to the next. We conclude that the prime driver of the on-going collapse of herd B is not high animal density or poor body condition. Accidents or disease seem unlikely as major causes of mortality. Predation, primarily by lynx and wolverine, appears to be the most plausible reason for the high female mortality and state of collapse in the studied reindeer herding community.
Highlights
Reindeer (Rangifer tarandus tarandus) herding in Sweden is a form of pastoralism practised by the indigenous Sami population
We present the results of research into female survival using capture and recapture records of individually marked female reindeer, collected over five years, together with results on body mass and calving success and official statistics on reindeer numbers and harvest, to examine possible reasons for the observed negative herd development and poor production in Njaarke reindeer herding community
Until 2001, the annual herd growth rate was on average 0.40%, which was balanced by a harvest of 501–715 reindeer per year, keeping the herd size stable
Summary
Reindeer (Rangifer tarandus tarandus) herding in Sweden is a form of pastoralism practised by the indigenous Sami population. The economy of reindeer husbandry is mainly based on meat production. Reindeer densities are normally regulated by harvest (slaughter) and intentionally kept below the ecological carrying capacity to enable sufficient harvest [1] (see Text S1 for details). Body condition is mostly maintained at a relatively high level. Winter survival is enhanced by providing the reindeer with supplementary feed if needed to prevent possible malnutrition caused by adverse snow conditions (e.g. thick hard snow or ice). Female body condition may affect calving success and early calf survival [2], and thereby the herd growth (and possibility for harvest), but is not expected to be the ultimate driver of population size
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