By : Daniela Castellanos
What is a mesopredator?
The food web is an intricate and interconnected network of relationships between consumers and producers. We often hear about animals that are at the “top of the food chain,” these are our apex predators (e.g. wolves, bears, lions, etc.). But what about the smaller animals, who are often omnivorous and feed on smaller prey in the food chain? These are the middle-ranked predators or ‘mesopredators’.
This section of the food web (i.e. mesopredators) is just as important to ecosystem balance.
Why are mesopredators so important?
Like all species across the trophic levels, mesopredators have an important role in the food web. Mesopredators control populations of smaller herbivorous animals who, if left to run rampant, would consume all of our primary producers (e.g. plants) and leave us without sources of food. Some examples of mesopredators are foxes, fishers, skunks, raccoons, weasels, minks, martens, etc.
Mesopredators have a dual role in the food web of consumers of smaller species and potential prey for larger animals.
Who are our mesopredators in Ontario?
The Land Between is home to a range of mesopredator mammals from the fisher to the pine marten from the south, and the river otter from the north. We also are home to the mink, racoon, skunk and the muskrat.
Many of the mesopredators mammals found in Ontario have a similar appearance since many of them belong to the Mustelidae family. This family (with the exception of sea otters) has an odorous gland (think of skunks) that creates a strong scent used to mark their territory and for sexual signalling.
Mink? Marten? Or Fisher? Mesopredators in our backyards.
Fisher (Martes pennanti).
This small mammal is similar to weasels and about the size of a fox. Fishers have a long body with short legs, sharp teeth, round ears and a bushy tail. Much like cats, fishers have retractable nails, making them excellent climbers. The fisher’s range expands across the northern U.S. and Canada. Their diet consists of small mammals (e.g. mice, porcupines, squirrels, hares, shrews, other carnivores, etc.) and birds; they are also opportunistic hunters.
Fun Fact: Fishers are specialists at hunting porcupines. They target the porcupine’s head because it has no quills, and circle or entrap their prey on a tree branch then attack its exposed face. Once the porcupine is disoriented, the fisher will attack the neck and feed on its underbelly.
Fishers tend to prefer habitats with high canopy enclosures and coniferous trees, but will also occupy mixed and deciduous forests.
Along with American martens, fishers are the only predators of their size that are agile in trees and are able to stretch into small cavities and holes to seek their prey. For the most part, adult Fishers are safe from predation, but kits are vulnerable to predation from hawks, red foxes, lynx and bobcats.
Fishers play an important role as predators in their ecosystem as they compete with other predators such as foxes, bobcats, lynx, coyotes, wolverines, American martens and weasels for food. This competition among predators is important to manage predator population levels. Also, since fishers are such specialized porcupine hunters, they help control porcupine populations.
American marten (Martes americana).
Also known as Pine Marten, American martens are cat-sized predators that have light brown- dark brown-gold coloured bodies with dark tails and legs. Similar to the Fisher, the American marten’s range spans from the northern US and Canada, and it is even found much further into the northern tree limit of Alaska. Their diet also consists of rodents, hares, birds, and occasional bird eggs, insects, fruits and carrion. For the most part, their diets are based on food availability, and they are opportunistic hunters. Although American martens spend a large portion of their time up in trees, they do most of their hunting on the ground. American Martens influence prey populations and predator interactions within their ecosystems.
Fun Fact: A group of American martens is called a “Richness”.
American mink (Neovision vison).
American mink are medium-sized, semi-aquatic carnivores with short ears, short legs and long tails. They have dark brown fur with a white chin and markings on the throat, chest and belly. Their toes are partially webbed and their fur is waterproof, as part of their semi-aquatic nature. Females are usually much smaller than males.
American mink is native to the US and Canada; however, they have been introduced to parts of Europe, Asia and South America through fur farms with some populations establishing due to accidental escapes. American mink feed on small mammals, waterbirds, small invertebrates, amphibians, reptiles and fish. Being opportunistic predators, they will also consume eggs, aquatic insects, hares, worms and snails. Mink have a strong impact on their environment, this is especially evident in their introduced ranges. For example, mink introduction in Europe has negative impacts on bird (especially ground nesters and waterbirds), small mammals (e.g. voles and muskrats) and amphibian populations.
Fun Fact: Mink purr when they are happy!
How can we tell these mesopredators apart?
American Mink |
American Marten |
Fisher  |
|
| Habitat: | Near water | Woodland | Woodland |
| Size: | Cat-sized~ 12-16” head to tail and about 1-2.5 pounds. | Cat-sized~ 18-25” head to tail and about 1- 4 pounds | Fox-sized~ 17-31” head to tail and 4-12 pounds |
| Colour: | Dark brown or black | Light brown- dark brown- gold bodies with a dark tail and legs | Deep brown or black; can be gold or silver due to tricoloured guard hairs |
| Ears: | Round and dark | Pointed with pale fur | Dark, wide and round ears |
| Throat markings: | Might have patches of white | Cream coloured bib | No distinct markings |
| Tail: | Slightly bushy | Long and bushy | Long and bushy |
| Legs: | Short | Long | Short |
Mesopredators around the world.
Based on their place in the food web, mesopredators around the world share a common dynamic within their own ecosystems. They are opportunistic hunters that will consume whatever is most available and have the capacity of taking over food webs in the absence of apex predators. Since in almost all ecosystems, humans have altered the interactions within food webs, there have been changes in the abundance of mesopredators around the world. The control of mesopredators normally occurs in either top-down forces – where the apex predator controls the population through predation and competition or bottom-up forces – where food availability is the limiting factor that controls the population. In the case where there is an absence of apex predators, there is a phenomenon that is called ‘the mesopredator release ’.
Mesopredator release. This occurs when the apex predator is removed from the ecosystem, allowing some mesopredators to thrive and to have a population increase. This has occurred in many ecosystems around the world. An example of mesopredator release occurred to baboons in South Africa. Here, most apex predators have been removed by poachers, disease or land conversion. This mesopredator release greatly favoured baboons. Demonstrated through a 365% increase in baboon observations and a 500% range increase. The population and range increase became problematic for farmers who reside close to the protected areas because baboons are able to consume an entire year’s crop. This has led farmers to adopt creative crop management strategies to protect their lands from crop-raiding baboons.
Mesopredator release… So what?
The changes in food web dynamics affect some if not all of the animals that are part of the ecosystem. Since mesopredators are found lower on the food chain, their overabundance can have a greater impact on more species because mesopredators are often generalist and opportunistic predators (in comparison to apex predators). As one type of mesopredator increases in abundance, it will create more pressures on prey species, other mesopredators and humans.
Mesopredators play an essential role in the ecosystem by controlling population levels in the lower trophic layers of the food chain. The issue associated with mesopredator release comes from rapid changes in the ecosystem, this includes habitat change, removal of apex predators and increased human disturbances.
How can we help?
Since mesopredator population control is most effective through top-down control, ie. when apex predators control the abundance of those lower in the food chain. We need to help conserve apex predator populations. One way is by protecting habitat continuity.
Mesopredator release is most common in fragmented habitats since these areas cause three things: 1. A reduction of available habitat for apex predators that need larger home ranges to survive. 2. An increased number of human-apex predator interactions, and no one wants to have close interactions with them! 3. At the same time, fragmentation causes close interactions between people and mesopredators, and therefore more access to food, trash, crops and pests ~ allowing for population growth.
Although the fisher, American mink and pine marten are not experiencing mesopredator release, they do compete with species that are experiencing mesopredator release, such as the coyote. If we want our ecosystem to find a balance and the food web to be restored, we must work together to maintain our natural habitats. Also, an everyday way to help the critters in your backyard is to please refrain from feeding wildlife because the negative effects of these actions can be detrimental to our ecosystems. Click here to read more about the dangers of feeding wildlife.
Next time you see one of these small carnivorous mesopredators in your backyard you will be able to identify and appreciate their important role in our ecosystem!
Sources:
Avenant, N. L., Drouilly, M., & Melville, H. I. A. S. The role of mesopredators in ecosystems: potential effects of managing their populations on ecosystem processes and biodiversity. Livestock Predation and its Management in South Africa: A Scientific Assessment, 205.
Ellis, E. 1999. “Martes americana” (On-line), Animal Diversity Web. Accessed December 16, 2021 at https://animaldiversity.org/accounts/Martes_americana/
IUCN/SSC Invasive Species Specialist Group (ISSG), Anderson, C., Maley, B., Institute of Ecology, & University of Georgia. (2019, November 19). Neovison vison (American mink). Https://Www.Cabi.Org/Isc/Datasheet/74428#tocontributors. Retrieved December 16, 2021, from https://www.cabi.org/isc/datasheet/74428#toidentity
Powell, R. A., Buskirk, S. W., & Zielinski, W. J. (2003). Fisher and marten. Wild Mammals of North America: Biology, Management, and Conservation, p. 635-649.
Prugh, L. R., Stoner, C. J., Epps, C. W., Bean, W. T., Ripple, W. J., Laliberte, A. S., & Brashares, J. S. (2009). The rise of the mesopredator. Bioscience, 59(9), 779-791.
Rhines, C. 2003. “Martes pennanti” (On-line), Animal Diversity Web. Accessed December 16, 2021 at https://animaldiversity.org/accounts/Martes_pennanti/
Ripple, W. J., Wirsing, A. J., Wilmers, C. C., & Letnic, M. (2013). Widespread mesopredator effects after wolf extirpation. Biological Conservation, 160, 70-79.
Schlimme, K. 2003. “Neovison vison” (On-line), Animal Diversity Web. Accessed December 16, 2021 at https://animaldiversity.org/accounts/Neovison_vison/
Taylor, R. A., Ryan, S. J., Brashares, J. S., & Johnson, L. R. (2016). Hunting, food subsidies, and mesopredator release: the dynamics of crop‐raiding baboons in a managed landscape. Ecology, 97(4), 951-960.
Vincent Wildlife Trust. (n.d.). How to tell a pine marten from a mink or feral ferret. Https://Pinemarten.Ie. Retrieved December 16, 2021, from https://pinemarten.ie/wp-content/uploads/2018/11/pinemartenhubpmminkorferretlatest1-1.pdf
The Land Between: Regaining Our Balance With Biodiversity
Leave a Reply