Data from: Behavior and nutritional condition buffer a large-bodied endotherm against direct and indirect effects of climate

Temporal changes in net energy balance of animals strongly influence
fitness; consequently, natural selection should favor behaviors that
increase net energy balance by buffering individuals against negative
effects of environmental variation. The relative importance of behavioral
responses to climate-induced variation in costs versus supplies of energy,
however, is uncertain, as is the degree to which such responses are
mediated by current stores of energy. We evaluated relationships among
behavior, nutritional condition (i.e., energetic state), and
spatiotemporal variation in costs versus supplies of energy available to a
large-bodied endotherm, the North American elk (Cervus elaphus), occupying
two ecosystems with contrasting climates; 1) a temperate, montane forest;
and 2) an arid, high-elevation desert. We hypothesized that during spring
through autumn, behavioral responses to the energetic landscape would be
both context-dependent (i.e., would vary as a function of the
environmental conditions experienced by elk in the forest versus the
desert), and state-dependent (i.e., would vary as a function of the
energetic state of an individual). We tested several predictions derived
from that hypothesis by combining output from a biophysical model of the
thermal environment with data on forage quality, animal locations, and
nutritional condition of individuals. At the population level, elk in the
desert selected areas that reduced costs of thermoregulation over those
that provided the highest quality forage. In the forest, however, costs
imposed by the thermal environment were less pronounced, and elk selected
areas that increased access to high quality forage over those that reduced
costs of thermoregulation. At the individual level, nutritional condition
did not influence strength of selection for low-cost areas or high quality
forage among elk in the forest. In the desert, however, strength of
selection for low-cost areas (but not forage quality) was state-dependent
- individuals in the poorest condition at the end of winter showed the
strongest selection for areas that reduced costs of thermoregulation
during spring and summer, and also expended the least amount of energy on
locomotion. Our results highlight the importance of understanding the
roles of behavior and nutritional condition in buffering endotherms
against direct and indirect effects of climate on fitness.