2.2.1: Mammals

Figure \(\PageIndex{1}\): Deer mouse in its natural habitat. Gregory "Slobirdr" Smith, CC BY-SA 2.0, via Wikimedia Commons

Mammals are what comes to mind for most people when discussing wildlife biology. They are vertebrates that have fur, have live birth (with two exceptions), feed their young milk, and generally have a lot of parental care as offspring. These life history patterns help give their young a head start in survival, but also require a lot of parental energy.Some species are managed by wildlife biologists because they are causing a nuisance to humans or other parts of the ecosystem; others are managed because their populations have been drastically reduced. Mammals can be divided into several groups, based on their species characteristics.          

Rodents

Rodents include such species as mice, rats, squirrels, and other gnawing mammals. Although some species are endangered (for example, the various subspecies of Peromyscus polionotus beach mice), and are managed by agencies involved with enforcing the Endangered Species Act. Other species, however, are often managed as nuisance species. Deer mice (Peromyscus maniculatus) are notorious carriers of hanta virus, which can cause severe respiratory illness in humans. Deer mice are often found in rural cabins or abandoned structures. If found, the structure must be cleaned and disinfected before habitation is safe again.

Two other species of gnawing mammals are ground squirrels (scientific name) and prairie dogs (scientific name). These are both burrowing mammals can carry the bubonic plague, the plague that decimated Europe in the 1300s. Ground squirrels tend to live closer or even within residential areas, whereas prairie dogs live in open grasslands, often far from people. Close contact with either species should be avoided. Bubonic plague is now treatable with antibiotics, but early detection is the key.

Gnawing mammals that can cause damage to structures or landscapes include grey squirrels (scientific name)  and beavers. Often, grey squirrels will chew holes through structures and take up residence in the attic, where they must be trapped and removed. Beavers cause damage to young trees that they use to build their dams, particularly near streams and other water bodies. When replanting a riparian habitat (one near a river or stream), young trees can be painted with a collar of sandy paint to prevent the beavers from felling the trees.

Rodents are typically r-selected species, which means they produce a lot of offspring, and often. Their populations can quickly get out of control when a community is missing its predators, such as hawks, coyotes, and owls. Management can include making spaces for predatory species to repopulate the area.

 

Ungulates

Ungulates, or hoofed mammals, typically form herds in the wild. They include organisms such as various species of deer, buffalo, antelope, elk, moose, and others. They can either be treated as nuisance species if they have no natural predators left in the ecosystem, or, in cases where their numbers are low due to historic hunting, they are protected. White tailed deer in particular tend to overrun suburban areas where there are no more natural predators. They eat yard plants, young trees, and cause a hazard on roadways when their populations are too big.

Some ungulates can be considered non-native species. Although wild horses were present on the North American continent millions of years ago, they went extinct there about 12,000 years ago. (Perrin, 2020) However, they continued to do well in Asia, where they still exist today. Wild horses currently in North America were brought over by European colonists, who had domesticated them. Once loose in North America, they were able to interbreed and produce distinct subspecies of wild horses again.

 

Carnivores

Carnivores, such as big cats, wolves and coyotes, and other similar large predators play a very important role in ecosystems. They are the top-down control of smaller animals, and without them, these smaller animals can overpopulate an area, sometimes very quickly. In areas where predators have been wiped out, reintroducing them can have cascading effects that heal the entire ecosystem.

A classic example of this top-down control is the reintroduction of wolves to Yellowstone National Park. In the short film “Wolves Change Rivers”, the reintroduction of wolves controlled the ungulate herbivore population, which allowed the banks of the rivers to revegetate. This then caused a cascading effect of increasing other mammal and bird populations, and also pollinator insects. Watch the film to get an idea of the far reaching effects of just reintroducing a top predator. Check out the video How Wolves Changed Rivers for more information.

 

Marine mammals

Marine mammals such as whales, seals, and otters used to be considered as fisheries for meat, oil, and fur. Their numbers were brought precipitously low at the height of the fishing effort. However, in most of the world, they are now protected in the U.S. under the Marine Mammal Protection Act and the Endangered Species Act, as well as CITES internationally. Unfortunately, the CITES treaty only applies to nations that are signatories. Japan, and to a smaller extent, Iceland, still fish for whales for meat, and seals are not protected everywhere.

Now, the one of the greatest threats to marine mammals is boat strikes. In Florida, the West Indian manatee was previously managed under the Endangered Species act by creating maximum speed zones in waters traveled extensively by them. However, in the interest of allowing for faster boats, unfortunately, the protection for these large, freshwater marine mammals has been scaled back in recent years.