Causes and consequences of movement : the interaction between foraging and landscape patterns

Foraging animals must move to search their environment for food. The given pattern of resources on the landscape, in space and time, shapes the resulting movement patterns of foragers: over evolutionary time, search strategies adapt to the environment, but foragers also respond to short-term changes in the resource distribution resulting from, for example, phenology or plant demographics. Foragers can also alter the landscape as they move, either physically or by facilitating gene flow, such that patterns of alteration in the landscape reflect the movement patterns of foragers. This two-way interaction between movement and landscape patterns sets up a feedback loop: the movement of dispersers alters the landscape upon which they likely base their subsequent movement decisions. In this dissertation, we investigate three aspects of this cyclical interaction in two different systems: crop-pollinating solitary bees in agroecosystems; and frugivorous, seed-dispersing primates in neotropical forests. First, we add phenological variation to an existing, spatially explicit simulation model of pollination services on agricultural landscapes in order to examine how mass-flowering events affect plant-pollinator interactions. Simulation results show that mass-flowering phenology benefits both crop pollination and specialist pollinators, but only when crop phenology and pollinator life-cycles are well synchronized. Second, we examine whether spider monkeys use topography in choosing their foraging routes between fruiting resources by comparing the power of two different movement models—a pure random walk and a model based on elevation—to explain observed foraging movements of spider monkeys in the western Amazon. Our elevation-based model explains the data significantly better than the null model, demonstrating that when given a choice between different routes, monkeys prefer higher-elevation pathways. Finally, in order to understand how spider monkeys shape forest structure through seed dispersal, we present a spatially explicit, agent-based simulation model that links foraging, seed dispersal, and forest growth in a closed cycle. Our results suggest that dispersal acts to condense tree distributions over the long-term, but at intermediate time-scales, it produces network-like landscape patterns that coincide with the spider monkeys’ travel routes.