Patchwork planet: the resource dispersion hypothesis, society, and the ecology of life

Abstract

Virtually nothing in nature is uniform. Observed at the right scale, most entities are clustered rather than evenly distributed, spatially and temporally, and this applies across domains from the distribution of matter in the universe, to habitats across the Earth's surface, and to energy in the landscape. Patchiness means organisms cannot carve out even territories. Instead, their shape and size depends on the dispersion of materials needed for survival and reproduction. This fundamental feature of life is intrinsically understood in ecology, for example, in the ideal free distribution and optimal foraging theory, and is represented in the anatomy as well as behaviour of organisms via the structures and strategies for moving, finding and capturing these patchy resources. But perhaps most striking of all is the role of patchiness in facilitating the formation of social groups – of societies. The resource dispersion hypothesis (RDH) suggests that where resources are dispersed and rich enough, multiple individuals can collapse into groups that share the same space at little cost to each other. Cooperation may be absent, but sociality is favoured nevertheless. Thirty years after the origin of the hypothesis, we review the accumulating models, critiques, evidence and experiments, concluding that RDH is a pervasive feature of animal spacing patterns across a wide range of species, taxonomic groups and ecosystems. In the spirit of the original objective of the Huxley Reviews to ‘suggest and inspire research that will improve our knowledge in the future’, we also take the opportunity to consider wider implications of the RDH. If we live and evolved on a patchwork planet, then we should expect broader effects. Indeed, we suggest that the RDH has played an important role in the evolution of cooperation, biodiversity, behaviour and, not least, in the social organization of humans in our evolutionary past and today.

Mesopredator Management: Effects of Red Fox Control on the Abundance, Diet and Use of Space by Feral Cats

“…Because cats increased their use of carrion, a resource previously favoured by foxes, we adduce this as evidence that foxes can affect cat-resource use, although further investigation is required to understand the broader implications. For instance, if more carcasses were available to cats at fox-removal sites we might expect cat home-ranges to be smaller at fox-removal sites relative to untreated sites [35–37]. This was apparent in our study, but only when those cats ( n = 7) whose home ranges were estimated for all three seasons were analyzed.…”

Carnivory maintains cranial dimorphism between males and females: Evidence for niche divergence in extant Musteloidea

“…Carnivorous musteloids exhibit the greatest degree of sexual dimorphism in cranial size and bite force, whereas herbivorous musteloids exhibit the lowest degree of sexual dimorphism. Following predictions of niche divergence, omnivorous and herbivorous musteloids exhibit reduced degrees of sexual dimorphism as nonvertebrate prey and plant material are more abundant and easier to obtain therefore reducing intraspecific competition (Hairston et al 1960;Noonan et al 2015;MacDonald and Johnson 2015). Because competition for terrestrial vertebrate prey is greater than for plant material, nonvertebrate prey (Hairston et al 1960;Noonan et al 2015;MacDonald and Johnson 2015), and aquatic vertebrate prey, increased sexual dimorphism is thought to reduce dietary competition between male and female carnivores under niche divergence.…”

“…It is well documented that males and females of many carnivoran species utilize different dietary resources, often in the form of prey size where males consume larger prey than females (Birks and Dunstone 1985;Funston et al 2001;McDonald 2002;Radloff and Toit 2004). This pattern is often attributed to the hypothesis that competition for vertebrate prey is likely greater than competition for plant material and nonvertebrate prey (Hairston et al 1960;Noonan et al 2015;MacDonald and Johnson 2015). This pattern is often attributed to the hypothesis that competition for vertebrate prey is likely greater than competition for plant material and nonvertebrate prey (Hairston et al 1960;Noonan et al 2015;MacDonald and Johnson 2015).…”

“…Furthermore, across carnivorans there is a relationship between the degree of carnivory and the degree of sexual dimorphism in which more carnivorous species exhibit greater size dimorphism between males and females (Gittleman and Van Valkenburgh 1997;Noonan et al 2016). In contrast, increased sexual dimorphism to reduce intraspecific competition is not necessary in species with a lower degree of carnivory (i.e., plant material, nonvertebrate prey) because these prey items are more abundant and easier to obtain (Hairston et al 1960;Noonan et al 2015;MacDonald and Johnson 2015). Increased sexual dimorphism in obligate carnivores, therefore, reduces intraspecific dietary competition by reducing competition between males and females.…”

The interplay between clumped resources, social aggregation, and genetic relatedness in the raccoon

“…However, in some species, groups form with seemingly no benefits. The resource dispersion hypothesis (Carr and Macdonald 1986;Johnson et al 2002;Macdonald and Johnson 2015) attempts to explain such scenarios by predicting that patchy, but abundant resources can result in social systems that support group living by enabling multiple individuals to share resources in an area without imposing significant costs on each other (da Silva et al 1994;Derocher and Stirling 1990;Gehrt and Fritzell 1998;Kruuk and Parish 1987;Rogers 1987).…”