THE ROLE OF MAMMALS AS ECOSYSTEM LANDSCAPERS

Abstract

The role of mammals in ecosystems is to modify vegetation structure, alter pathways of nutrients, and thereby change species composition. Their large-scale structuring effects make large mammals ‘ecological landscapers’. Through this they influence ecosystem function and biodiversity. Landscaping effects occur when mammals are regulated by food, rather than by predators. This condition is constrained by four factors: when (1) body size is large enough to avoid predators; (2) populations adopt large scale migration behaviour because predators are unable to follow them; (3) in multispecies communities (savanna, grasslands) with a range of predator and prey sizes, only the largest species can avoid predation because they subsidize predators that regulate smaller prey species; and (4) in single predator-prey systems (tundra, desert, boreal, and temperate forests), ecological conditions determine whether or not predators regulate prey. The structuring role of mammals in maintaining species diversity is evident not just in vegetation, but also in birds, other mammals, and invertebrates. This role makes them prime candidates as ‘umbrella species’ for conservation. Protection of large mammal species and their habitats also conserves a large part of the remaining community. It also means that such mammals become the ‘indicator species’ for the health of the ecosystem.