OOS 46-6 - Integrating animal body size and dynamic decision making into the study of animal-driven nutrient distribution - insights gained through mechanistic modelling.

Animals have the power to reshape nutrient landscapes, influencing resource availability, ecosystem productivity and species composition. As animals eat, defecate, and die in different places, they inevitably alter the flow of nutrients throughout their habitats. Current mathematical models designed to quantify such nutrient redistribution functionality, agree that animals play a decisive role in shaping the nutrient landscape. However, the predictions generated by these models are often very generalized and does not take into account the dynamic nature of environments and the ability of animals to adapt their behavior accordingly. More than just reorganizing nutrients in space, animals will respond to nutrient heterogeneity and to the emerging nutrient landscape that they themselves create. Moreover, species of different body size will vary in both their ability to redistribute nutrients and their ability to respond to nutrient patchiness. These differences will alter their tendency to accumulate or disperse nutrients and, in turn, affect the spatial patterning of nutrient redistribution.

We developed an individual-based model capable of incorporating animal behavior and flexibility in decision-making responses to a continuously changing nutrient environment. Particularly, our model explores the relationship between large mammal body size and the dynamics of wildlife-driven nutrient distribution. We demonstrate how the size-dependent selective feeding behavior of animals can alter the rate at which nutrients are transported from high to low concentration and the likelihood of nutrient accumulation. We show how the composition of mammal communities, and particularly the average community body size, can influence the heterogeneity of nutrient patterns across a landscape. Overall, our model demonstrates how mammal body size and selective feeding behavior are important drivers of the pattern and rate of nutrient distribution in a spatially complex and changing environment, and points to the intricate role of mammal communities on nutrient dynamics.