Spatial signature of resource distribution is mediated by consumer body size and habitat preference
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Abstract
Consumers shape spatial patterns on landscapes by amplifying or dampening environmental heterogeneity through feeding, excretion, and movement of resources. The degree to which the environment is modified by consumers depends on species’ traits, including body mass, movement and foraging behavior, and habitat specialization. Global change is altering the size and traits of consumer populations, but our understanding of how this may impact resource heterogeneity is limited. Here, we developed an individual-based model of habitat specialists’ and generalists’ movement and activity in a patchy landscape and investigated the impact of changes in population and mean body sizes on landscape-scale resource heterogeneity. We found that consumers specializing on low-resource habitats (a common risk avoidance strategy) increased spatial resource heterogeneity regardless of their population and body size. By contrast, generalists eroded differences among habitats, and we further found that resource heterogeneity decreased with the average body size of generalist consumers, even while controlling for total consumer biomass. Larger perceptual ranges increased the area over which generalist consumers could select foraging habitat, and reduced the extent to which they eroded landscape structure. These nuanced spatial outcomes of consumer-resource interactions emerge from how metabolic demands, which scale nonlinearly with body size, play out among habitat types which attract different consumers, as well as the scale at which those consumers make habitat selection decisions. Since global change disproportionately impacts larger species and specialists, indirect consequences on ecosystems may arise via biotic processes, affecting spatial heterogeneity of future landscapes.
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In ecosystems, living organisms are affected by their abiotic environment but also modify it. Because animal consumers have the ability to choose what and where they forage based on resource availability or predation risk, thereby shaping the spatial distribution of resources across the landscape. For example, it has been shown that high densities of herbivores can create resource hotspots through carcass deposition, or resource cold spots through grazing, thus increasing the overall heterogeneity of resources in the landscape (Ferraro et al. 2022). Resource spatial heterogeneity is known to foster species coexistence and biodiversity (Amarasekare 2003). As ongoing global change affects the composition of consumer communities, it is important to understand how animal populations can amplify or dampen resource heterogeneity at the …
In ecosystems, living organisms are affected by their abiotic environment but also modify it. Because animal consumers have the ability to choose what and where they forage based on resource availability or predation risk, thereby shaping the spatial distribution of resources across the landscape. For example, it has been shown that high densities of herbivores can create resource hotspots through carcass deposition, or resource cold spots through grazing, thus increasing the overall heterogeneity of resources in the landscape (Ferraro et al. 2022). Resource spatial heterogeneity is known to foster species coexistence and biodiversity (Amarasekare 2003). As ongoing global change affects the composition of consumer communities, it is important to understand how animal populations can amplify or dampen resource heterogeneity at the landscape. This task is particularly complex, as it involves several variables and processes. Furthermore, key characteristics of consumer populations, such as density or average body size, are both expected to be affected by global change.
Little et al. (2026) disentangled the various processes that determine how animal consumers affect resource spatial heterogeneity. They used an individual based model (NetLogo) that simulates herbivore movement on a grid composed of high-quality patches within a matrix of lower quality. The model integrates all the mechanisms involved in the general process of resource uptake (grazing) and deposition (feces, urine, and carcasses) by animal consumers at the landscape scale.
They designed a factorial simulation experiment to understand the individual and interactive effects of i) population density, ii) body size, iii) risk-based habitat preference, and iv) perceptual range on landscape-scale resource heterogeneity in a patchy landscape. Two distinct foraging strategies were associated with risk-based habitat preference: generalist (forage everywhere) and specialist (forage only in poor-quality patches to avoid predators). Key consumer traits such as movement distances, metabolic requirements and perceptual ranges all scale with body size.
They find that different foraging strategies of animal consumers had opposite effects on resource heterogeneity. While higher density or body mass of specialists increases resource heterogeneity at the landscape scale, increased biomass of generalists had a homogenizing effect on resource spatial distribution. They also find that increasing perceptual range of generalists maintains resource spatial heterogeneity by decreasing the spatial autocorrelation of resource uptake and deposition.
The authors nicely outline the ecological implications of the simulation results in the context of global change, which is associated with a decline in populations of large specialist consumers and a decrease in average body size of animals. They suggest that replacement of large specialists by small generalists could lead to a drastic erosion of resource heterogeneity across landscapes. This homogenization would likely reduce both the spatial clustering of nutrients, as well as the diversity of the plants serving as food resources. These findings are highly relevant for anticipating the consequences of global change across biological scales and shed new light on the effect of changes in the functional composition of animal consumers on landscape-scale resource distributions.References
Amarasekare, P. (2003), Competitive coexistence in spatially structured environments: a synthesis. Ecology Letters, 6: 1109-1122. https://doi.org/10.1046/j.1461-0248.2003.00530.x
Ferraro, K.M., Schmitz, O.J. and McCary, M.A. (2022), Effects of ungulate density and sociality on landscape heterogeneity: a mechanistic modeling approach. Ecography, 2022:. https://doi.org/10.1111/ecog.06039
Chelsea J. Little, Pierre Etienne Banville, Adam T Ford, Rachel M Germain (2026) Spatial signature of resource distribution is mediated by consumer body size and habitat preference. bioRxiv, ver.4 peer-reviewed and recommended by PCI Ecology https://doi.org/10.1101/2024.06.24.600507
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