Territorial pattern formation in the absence of an attractive potential

TL;DR

This paper develops a PDE model demonstrating that territorial patterns can form solely through conspecific avoidance and scent-marking, without the need for attraction to fixed spatial points, supported by analytical proofs.

Contribution

It introduces a PDE model based on individual behavior that explains territorial pattern formation without attraction, extending previous models to include scent detection scales.

Findings

Steady-state patterns form if scent decay is slow enough.

Pattern formation depends on scent detection range.

Analytical method for PDE limit of individual-based models.

Abstract

Territoriality is a phenomenon exhibited throughout nature. On the individual level, it is the processes by which organisms exclude others of the same species from certain parts of space. On the population level, it is the segregation of space into separate areas, each used by subsections of the population. Proving mathematically that such individual-level processes can cause observed population-level patterns to form is necessary for linking these two levels of description in a non-speculative way. Previous mathematical analysis has relied upon assuming animals are attracted to a central area. This can either be a fixed geographical point, such as a den- or nest-site, or a region where they have previously visited. However, recent simulation-based studies suggest that this attractive potential is not necessary for territorial pattern formation. Here, we construct a partial differential equation (PDE) model of territorial interactions based on the individual-based model (IBM) from those simulation studies. The resulting PDE does not rely on attraction to spatial locations, but purely on conspecific avoidance, mediated via scent-marking. We show analytically that steady-state patterns can form, as long as (i) the scent does not decay faster than it takes the animal to traverse the terrain, and (ii) the spatial scale over which animals detect scent is incorporated into the PDE. As part of the analysis, we develop a general method for taking the PDE limit of an IBM that avoids destroying any intrinsic spatial scale in the underlying behavioral decisions.