The effects of food abundance, foraging rules, and cognitive abilities on local animal movements

Abstract

Movement is nearly universal in the animal kingdom. Movements of animals influence not only themselves but also plant communities through processes such as seed dispersal, pollination, and herbivory. Understanding movement ecology is important for conserving biodiversity and predicting the spread of diseases and invasive species. Three factors influence nearly all movement. First, most animals move to find food. Thus, foraging dictates, in part, when and where to move. Second, animals must move by some rule even if the rule is "move at random." Third, animals' cognitive capabilities affect movement; even bees incorporate past experience into foraging. Although other factors such as competition and predation may affect movement, these three factors are the most basic to all movement. I simulated animal movement on landscapes with variable patch richness (amounts of food per food patch), patch density (number of patches), and variable spatial distributions of food patches. From the results of my simulations, I formulated hypotheses about the effects of food abundance on animal movement in nature. I also resolved the apparent paradox of real animals' movements sometimes correlating positively and sometimes negatively with food abundance. I simulated variable foraging rules belonging to 3 different classes of rules (when to move, where to move, and the scale at which to assess the landscape). Simulating foraging rules demonstrated that variations in richness and density tend to have the same effects on movements, regardless of foraging rules. Still, foraging rules affect the absolute distance and frequency of movements. In my third set of simulations, I simulated a range of spatial and temporal cognitive constraints and demonstrated that omniscience is not necessarily the optimal cognitive state from an energetic standpoint. I tested my hypotheses on the effects of food abundance with data from free ranging female black bears (Ursus americanus ) in Pisgah Bear Sanctuary (North Carolina, USA) and female kinkajous (Potos flavus ) in Parque Nacional Soberanía (Panama), two species with low predation risk. Depending on the season, black bear movements can be explained, by food patch richness, density or both richness and density. Female kinkajou move length correlated positively with patch richness and density. The number of moves of female kinkajous correlated negatively with patch richness of all foods that kinkajous eat and selectivity. In contrast, food patch richness and density did not affect male kinkajous' moves (length and number). Instead, male kinkajous increased foraging time on all foods that they eat as patch density decreased. Male kinkajous also decreased their selectivity on subsets of foods that they eat as patch richness increased. My results are broadly interesting because they demonstrate that the success of the habitat productivity hypotheses depends on how food is measured (patch richness or density), sex, species, and foraging and non-foraging behaviors (foraging selectivity, responses to moonlight).