This study tests the hypothesis that herd accumulation can be a risk reducing strategy aimed at increasing security in an unpredictable environment. Saami reindeer husbandry in Norway is characterized by environmental unpredictability and occasionally harsh winters can have dramatic negative effects on reindeer population densities. While herd accumulation has been found to be an adaptive risk reducing strategy in stochastic environments (i.e., individually rational), the accumulation of large herds may also result in collectively negative density dependent effects, which may negatively affect individual herders (i.e., collectively irrational). We found that individual husbandry units' strategies, such as accumulating reindeer, have a larger effect on individual husbandry units' herd size than a negative density-dependent effect.

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We thank the herders who participated in our games. Jon Mikkel Eira provided invaluable assistance in the field. Thanks as well to other members of the Eira family for their hospitality, to Katharina Olsen for translating our questionnaire into Norwegian and to two anonymous reviewers for their help in improving this manuscript.

For long-lived organisms, the fitness value of survival is greater than that of current reproduction. Asymmetric fitness rewards suggest that organisms inhabiting unpredictable environments should adopt a risk-sensitive life history, predicting that it is adaptive to allocate resources to increase their own body reserves at the expense of reproduction. We tested this using data from reindeer populations inhabiting contrasting environments and using winter body mass development as a proxy for the combined effect of winter severity and density dependence. Individuals in good and harsh environments responded similarly: Females who lost large amounts of winter body mass gained more body mass the coming summer compared with females losing less mass during winter. Additionally, females experienced a cost of reproduction: On average, barren females gained more body mass than lactating females. Winter body mass development positively affected both the females' reproductive success and offspring body mass. Finally, we discuss the relevance of our findings with respect to scenarios for future climate change.

A review of the literature concerning nomadic pastoralism reveals a prevalent assumption of a positive effect of labor inputs on pastoral production. However, studies that have tried to quantify the relationship between household labor availability and production are characterized by contradictory results where one reason may be related to the fact that nomadic pastoralists cooperate by sharing and exchanging labor. As a consequence, previous quantitative research may have neglected an important level of social organization. The prevalence of cooperative labor investment among pastoralists may indicate the presence of scale‐dependent effects of pastoral labor on production. This article aims at developing a conceptual model illustrating this possibility, where the scale dependent effects of labor inputs are conceptualized as changes in the relationship between the costs and benefits of labor at different levels of social organization. [nomadic pastoralism, labor, cooperation, production, modeling] SAMMENDRAG  En gjennomgang av litteraturen om nomadisk pastoralisme, avslører en utbredt forestilling om positiv effekt av arbeidskraft på pastoral produksjon. Til tross for dette har studier søkt å kvantifisere forholdet mellom tilgjengelig arbeidskraft og produksjon, gitt motstridende resultater hvor en årsak kan være at nomadiske pastoralister gjennom samarbeid, deler og utveksler arbeidskraft. Med andre ord kan tidligere studier ha oversett et viktig nivå av sosial organisering. Utbredelsen av arbeidsinvestering gjennom samarbeid, synes å antyde tilstedeværelsen av skalaavhengige effekter av pastoral arbeidskraft på produksjon. Artikkelens mål er å utvikle en konseptuell modell som illustrerer denne muligheten, hvor de skalaavhengige effektene av arbeidskraft består av endringer i forholdet mellom kostnader og fordeler ved arbeidsinvestering på forskjellige nivåer av sosial organisering.