Mesopredators vary across different ecosystems. Sometimes, the same species is a mesopredator in one ecosystem and an apex predator in another ecosystem, depending on the composition of that ecosystem.[3] When new species are introduced into an ecosystem, the role of the mesopredator often changes; this can also happen if species are removed.[4]
When populations of an apex predator decrease, populations of mesopredators in the area often increase due to decreased competition and conflict with the apex predator.[2] This is known as the mesopredator release effect, which refers to the release of mesopredators from the trophic cascade.[5] These mesopredator outbreaks can lead to declining prey populations, destabilized ecological communities, reduced biodiversity, and can even drive local extinctions.[2][4]
Typically, mesopredators are in competition with apex predators for food and other resources.[2] Apex predators reduce mesopredator populations and change mesopredator behaviors and habitat choices by preying on and intimidating mesopredators.[6] When apex predator populations decline, mesopredators can access hunting and den areas once controlled by the apex predators, essentially assuming the role of an apex predator.[2] However, mesopredators often occupy different ecological niches than the former apex predator and will have different effects on the structure and stability of the ecosystem.[3][4]
Mesopredator outbreaks are becoming more common in fragmented habitats, which are areas where a species' preferred environment is broken up by obstacles.[4] Fragmented habitats can be caused by geological or human activity, and particularly affect larger animals that roam and hunt across large territories, such as apex predators.[7] Fragmented habitats can drive these species to leave and find more suitable habitats.[4]
Additionally, in many fragmented habitats, apex predators have more encounters with humans, leaving them susceptible to harmful or deadly conflicts, sometimes resulting in eradication of the apex predator population entirely.[4] Human development also promotes mesopredator outbreaks through increasing access to resources such as pet food, trash, and crops.[4]
The mesopredator release effect is not entirely understood. Most research has been conducted on mammal species, with limited studies on non-mammal animal species.[3] Additionally, it is not well understood how these dynamics may play out in ecosystems with many mesopredator and apex predator species.[3]
^ abcdefghPrugh, Laura R.; Stoner, Chantal J.; Epps, Clinton W.; Bean, William T.; Ripple, William J.; Laliberte, Andrea S.; Brashares, Justin S. (2009-10-01). "The Rise of the Mesopredator". BioScience. 59 (9): 779–791. doi:10.1525/bio.2009.59.9.9. ISSN0006-3568. S2CID40484905.