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A mesopredator is a mid-ranking predator in the middle of a trophic level, which typically preys on smaller animals. Mesopredators often vary in ecosystems depending on the food web. There is no specific size or weight restrictions to qualify as a mesopredator. It depends on how large the apex predator is, and what the mesopredator's prey is. When new species are introduced into an ecosystem, the role of mesopredator often changes; the same happens if a species is removed.
The Mesopredator Release Effect
When populations of apex predators decrease, populations of mesopredators often increase. This is the mesopredator release effect. These mesopredator outbreaks can lead to declining prey populations, destabilize communities and even driving local extinctions. When apex predators are removed from the ecosystem, this gives the mesopredators less competition and conflict. They are able to catch more prey and have lower mortality rates. Often mesopredators can take over the role of apex predators. This happens when new species are introduced into an ecosystem or when species leave or are killed off. Former mesopredators are not ecologically identical to the former apex predator (likely being a smaller species), and will have different effects on the structure and stability of the ecosystem. All mesopredators in the ecosystem benefit from this mesopredator release. Apex predators reduce mesopredator populations and change mesopredator behaviors and habitat choices by preying on and intimidating mesopredators. This occurs in any ecosystem with any type of relationship between predator and prey. However, in the case of the relationship between apex predator and mesopredator, it could mean that the apex predator causes the mesopredator to leave the ecosystem, creating room for new species to become mesopredator.
Mesopredator outbreaks are increasing in fragmented habitats. A main cause of this is the disappearance of apex species within the habitat. Apex species are usually larger animals which require a bigger area and will often leave if the habitat is lost. When the apex predator leaves the ecosystem, a former mesopredator will become the new apex predator. In addition to this, apex predators, being larger animals, often have more encounters with humans, leaving them more susceptible to harmful conflicts. These harmful conflicts can cause the apex predator to leave the ecosystem in fear of danger, or, if the situation is extreme enough, the humans can kill off the apex predator population entirely. Mesopredator outbreaks are also becoming more prevalent as certain resources which can be consumed by these species (such as pet food, trash, crops, and crop pests), are being added in fragmented areas. These resources often appear when development is occurring on land near or within the ecosystem, creating ideal conditions for mesopredator outbreaks to occur.
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