Density-dependent habitat selection alters drivers of population distribution in northern Yellowstone elk

Although it is well established that density dependence drives changes in organismal abundance over time, relatively little is known about how density dependence affects variation in abundance over space. We tested the hypothesis that spatial trade-offs between food and safety can change the drivers of population distribution, caused by opposing patterns of density-dependent habitat selection (DDHS) that are predicted by the multidimensional ideal free distribution. We addressed this using winter aerial survey data of northern Yellowstone elk (Cervus canadensis) spanning four decades. Supporting our hypothesis, we found positive DDHS for food (herbaceous biomass) and negative DDHS for safety (openness and roughness), such that the primary driver of habitat selection switched from food to safety as elk density decreased from 9.3 to 2.0 elk/km(2). Our results demonstrate how population density can drive landscape-level shifts in population distribution, confounding habitat selection inference and prediction and potentially affecting community-level interactions.

Automated summary

While the impact of density dependence on temporal changes in population abundance is well understood, little is known about its effects on spatial variation in abundance. This study investigated how spatial trade-offs between food and safety influenced population distribution in northern Yellowstone elk over a four-decade period. The results revealed a shift in habitat selection from food to safety as elk density decreased, highlighting the importance of population density in driving landscape-level shifts in distribution and potentially affecting community-level interactions.