# Mesopredator

A mesopredator is a predator that occupies a mid-ranking trophic level in a food web. There is no standard definition of a mesopredator, but mesopredators are usually medium-sized carnivorous or omnivorous animals, such as raccoons, foxes, or coyotes. They are often defined by contrast from apex predators or prey in a particular food web. Mesopredators typically prey on smaller animals.
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. When new species are introduced into an ecosystem, the role of the mesopredator often changes; this can also happen if species are removed.
The American Institute of Biological Sciences states that due to the fact that mesopredators are smaller than large carnivores, they are more abundant, and therefore have greater diversity of mesopredator species.[2] Due to their smaller size, mesopredators play a part in the ecosystem of dispersing seeds in open spaces, as well as driving community structure.[2] Mesopredators are also very diverse in comparison to larger carnivores in their behaviour and ecology, from being reclusive to highly social. Their diversity and small size allows them to thrive in a range of habitats than larger carnivores are able to.[2] The population of these smaller carnivores also increases when the presence of a larger carnivore decline. This is known as the 'mesocarnivore release.' According to the National Park Service, "Mesocarnivore release is defined as the expansion in range and/or abundance of a smaller predator following the reduction or removal of a larger predator."[6] One impact of this is that these mesopredators can act as scavengers cleaning up dead animal carcasses discarded by humans in urban areas.[7] Mesopredators' habitat have shifted and changed, due to urbanisation, leading to habitat fragmentation and disturbance, resulting in habitat loss for animals.

## Mesopredator release effect

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. This is known as the mesopredator release effect, which refers to the release of mesopredators from the trophic cascade. These mesopredator outbreaks can lead to declining prey populations, destabilized ecological communities, reduced biodiversity, and can even drive local extinctions.
Typically, mesopredators are in competition with apex predators for food and other resources. Apex predators reduce mesopredator populations and change mesopredator behaviors and habitat choices by preying on and intimidating mesopredators. 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. 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.
Mesopredator outbreaks are becoming more common in fragmented habitats, which are areas where a species' preferred environment is broken up by obstacles. 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. Fragmented habitats can drive these species to leave and find more suitable habitats.
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. Human development also promotes mesopredator outbreaks through increasing access to resources such as pet food, trash, and crops.
The mesopredator release effect is not entirely understood. Most research has been conducted on mammal species, with limited studies on non-mammal animal species. Additionally, it is not well understood how these dynamics may play out in ecosystems with many mesopredator and apex predator species.