Mammals are a highly diverse group of vertebrates present in the Upper Delaware Region. Mammals range widely in form and appearance, from Big Brown Bats to Porcupines to humans. Although a highly diverse group, mammals do share some important characteristics. All mammals produce milk to feed their young, have hair or fur, and are endothermic, also known as warm-blooded. In addition, all mammals have a jawbone that articulates with the skull in a way that is unique to mammals. Almost all mammals give birth to live young, except for the platypus and echidna, which are not present in the Upper Delaware Region.
Gray Fox
Scott Rando
Mammals' diets vary extensively by species. Some mammals are carnivorous, meaning they consume meat, while others are herbivorous, meaning they consume plant material. Many mammals are omnivorous, eating both meat and plant material. Mammals are also often opportunistic and take advantage of the food sources available to them. For example, the Gray Fox and Red Fox may prefer to feed on small game like the Eastern Cottontail, but they will also consume fruit, vegetables, insects, frogs, and even garbage. Black Bears and Raccoons are also opportunistic feeders. However, not every mammal is an opportunist. For example, bats in the Upper Delaware Region feed primarily on nighttime flying insects. They can catch insects midflight by using echolocation. Bats emit high-frequency sounds through their mouth or nose, and the sound waves bounce off objects in their environment, which allows them to determine the size, shape, and even texture of the object.
Black Bear
Scott Rando
Within an ecosystem, different mammal species play a variety of roles. For example, in this region Black Bears are apex predators, meaning they are at the top of the food web and no other animals hunt them. Mammals like moles, voles, and squirrels are farther down on the food chain and consumed by other mammalian predators like the Red or Gray Fox. Mammals also play roles in an ecosystem that are beyond the food chain. For example, Beavers modify the environment to create new habitats for themselves, and in turn, create habitat for other animals too. They build dams made of branches and mud that form slow-moving ponds. These ponds generate habitats for amphibians, fish, birds, and more.
Eastern Chipmunk
Scott Rando
Mammals can be found all over the Upper Delaware Region. Most mammals live on land, but some spend significant amounts of time in water as well. The River Otter, Beaver, and Muskrat are semi-aquatic species, meaning they often move between aquatic and terrestrial habitats. For example, the River Otter is equally comfortable running on land as swimming in the water. Their young quickly learn to swim at two months when their mother pushes them into the water. River Otters may be seen playfully sliding down snowy or muddy hills, splashing into the water. Some terrestrial mammals like the White-tailed Deer and Gray Squirrel are easily spotted in the park while others remain more elusive. For example, the Star-nosed Mole and Meadow Vole are rarely seen as they spend much of their time tunneling underground.
Little Brown Bat
Scott Rando
Although some mammals, like Raccoons, are expanding their range and moving into urban environments, others like the Little Brown Bat and Northern Long-eared Bat are at risk and declining in numbers. These bat species are declining due to white-nose syndrome, a disease that can be identified by a white fungus growing on a bat's muzzle or wings. White-nose syndrome attacks bats as they are hibernating and causes them to awaken prematurely and display strange behaviors like flying during the daytime. This abnormal activity depletes their winter fat reserves, causing them to starve as they cannot forage on their usual food sources in the wintertime.
Mammals found in the Upper Delaware Region include:
