Collared (Dicrostonyx groenlandicus) and brown (Lemmus trimucronatus) lemmings coexist in tundra habitats across much of the middle and lower Canadian arctic. Their coexistence, and response to predation risk, appears mediated by behavior. We analyzed field-collected videos of open-field tests to assess potential differences in innate behaviors between the two species. Collared lemmings were less active and exhibited less exploratory behavior than did brown lemmings, which were more active under cover than in the open. Similar behaviors scaling along axes of activity and curiosity were revealed by principal components analysis. Each axis defined different aspects of brown lemming personality, but repeated testing of the same individuals yielded a striking dependence of their behavioral response on open-field treatments. Even so, the differences between species in behavior correlate well with their habitat preferences that resolve competition and govern their coexistence.

Rapid changes affecting northern ecosystems and peoples are many and varied: demand for land and resources; expanding infrastructure and industry; global warming; pollution of land, air, and water from both distant and local sources; new and invasive species; and increasing human population growth and migration. The consequences of these changes include reduced ice and snow cover; permafrost thawing; erosion; rising sea levels; increasing contaminant levels; diminished native biodiversity; risks to human health, welfare, and infrastructure; and lost cultural and linguistic identity. Although capacity within the North to address and manage the consequences of change is improving, the North does not exist independent of other regions, and human impacts on the Arctic are harbingers of impending change elsewhere. The causes and consequences of rapid change are shared by humans and ecosystems at all latitudes.