Rodents and forests | Information, Sports activities, Jobs

The forests of northern Lower Michigan are inhabited by many types of flora and fauna. This biodiversity generally correlates with complexity. More complex forests tend to be more biodiverse, with some forest ecosystem types generally more complex than others.

Understanding how different the complexity is between different types of forest ecosystems, and incorporating this information into management, are keys to maintaining well-functioning forests and harnessing the added benefits for biodiversity and society. Forest planners and managers are increasingly realizing that they need to understand how forests function naturally if they are to be managed in an environmentally sustainable manner. Different types of forests need to be managed differently to maintain complexity, especially in their wildlife communities.

“Wildlife” is a slang term for non-domesticated animals. In most cases, the term wildlife refers to species with a backbone (vertebrate) that are of human interest because they are wild species (e.g., white-tailed deer, predator) that are aesthetically pleasing (e.g., loons, Bald eagles, many songbirds) or are (by some) considered pests (e.g. American beaver, species of mice).

While black bear, moose, white-tailed deer, coyote, and bobcat can all fall into the category “Charismatic Megafauna” Most of our native wildlife are relatively small and nondescript. In fact, of the approximately 52 mammalian species found in Northern Lower Michigan, 21 species (40%) are rodents (taxonomic order Rodentia, see “Mammals of the Great Lakes Region” 2001).

Our largest rodent, the American beaver, is considered to be one “Key types” – The presence of this species has a direct impact on the habitat of a wide range of other species. While beavers kill trees in forests to obtain food and building materials for lodges and the dams that form beaver ponds, these actions embody the complexity of the forests. In fact, data from Northern Minnesota was in “Biber: Boreal Forest Engineers” (2017) suggested that 124 species of native wildlife used beaver ponds. If a forest owner is genuinely interested in biodiversity, they should appreciate most (maybe not all) beavers.

Smaller rodent species are also important in maintaining forest complexity. For example, deer mice can be very common in some forest ecosystem types, especially oak forests. As such, deer mice are common prey for a wide variety of predators, from birds of prey such as broad-winged hawks and great horned owls to other mammals such as foxes and many species of weasels.

What is more surprising, however, is that deer mice themselves act as predators. For example, various stages of development of the exotic, invasive gypsy moth are often eaten by deer moths. In an article in the journal Environmental Entomology (1974), data from New England suggested that small mammals, particularly deer mice, were heavily infested with gypsy moth pupae, especially female pupae. After cyclical population outbreaks of gypsy moths, rodent, insect, parasite, and fungal and bacterial pathogens remain in abundance. Ultimately, these predators and pathogens will reduce the number of gypsy moths until the next outbreak.

Deer mice can also affect a forest by chasing seeds from trees. In an article in the journal Ecology (2010), data suggested that deer mice reduced both the incidence and settlement of seedlings in burned and unburned coniferous forests. In other words, deer mouse predators on conifer seeds created a patchy pattern of tree regeneration and promoted the complexity of the forest, not its evenness.

Another study in southern Michigan published in the journal American Midland Naturalist (1976) documented how red squirrels and fox squirrels can consume spring buds from deciduous trees. Maple buds in particular were consumed when other foods (such as acorns and other nuts) were not found or were only available in limited quantities. The diversity of tree species in the forests provides these rodents with alternative food resources, especially in late winter and early spring.

Wildlife habitat has a species-specific definition. In other words, every species of wildlife has its own habitat. Therefore, when we talk about the biodiversity of forests, we need to talk either about the habitat of each species or the expected forest patterns, which are based on how different forests naturally develop over time. When talking about biodiversity, this is often taken into account “Ecosystems”: biological entities and their abiotic (non-living) environment.

There is a general consensus in the forest ecological literature that most forest management activities tend to simplify forests. Therefore, explicit consideration must be given to finding ways to maintain the complexity of managing forests. Fortunately, our understanding of how to deal with complexity has increased significantly over the past 30 years. Sharing this information with private landowners must be a priority for everyone involved in forest planning and management.

For more information on Michigan’s mammals, visit iNaturalist: https://www.inaturalist.org/projects/mammals-of-michigan.

Greg Corace is the ranger of the Alpena-Montmorency Conservation District. For more information, including the sources used in this article, Greg can be contacted by email (greg.corace@macd.org) or phone (989-356-3596 x102).

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