critical decisions: risk allocation in a model arthropod (folsomia candida)
abstract
risk allocation theory predicts that foraging animals moderate predation risk by
allocating their foraging effort and space use according to their energetic demands.
undernourished animals have a greater need for energy than do sated individuals and
should accept higher risk while foraging. original theory predicted that the proportion of
time that individuals spend in good conditions primarily determines risk allocation. more
recent theory predicts that the length of exposure to good or bad conditions governs risk
allocation decisions when patterns of environmental risk are autocorrelated in time. i
investigate the effects of these factors with controlled experiments on a standard
arthropod (folsomia candida). i subjected animals to nine temporally autocorrelated 16-
day feeding treatments varying in both the proportion (0, 0.25, 0.50 and 0.75) and
duration (short, medium and long intervals) of time when food was absent. risk
allocation was assessed by the choice of occupying a risky dry habitat where food was
present (rich) versus a safe moist habitat with no food (poor). irrespective of
autocorrelation in conditions, the proportion of time spent with no food primarily
determined risk allocation by these collembolans. the results suggest an energetic
threshold below which f. candida are forced to forage in rich and risky habitat despite
the possibility of mortality through desiccation. state dependent patterns of habitat
selection suggest that understanding the relationship between energetic state and patterns
of environmental condition may allow us to employ risk allocation as a leading indicator
of habitat change.