Mammals are warm-blooded vertebrates which, with the exception of a few species, give birth to and nurse live young and have bodies insulated by hair. Many different types of mammals live in the Chesapeake Bay watershed or visit each year. Some live either on land or in the water, while others spend time in both environments. Notable mammals native to the watershed are bats, squirrels, humans, foxes, rabbits and dolphins.

Bottlenose dolphin

Image courtesy NASA/Wikimedia Commons

Bottlenose Dolphin (Tursiops truncatus)

The bottlenose dolphin (Tursiops truncatus) is a large, grayish aquatic mammal that visits the lower and middle Chesapeake Bay in summer. It is usually found in warm, salty open waters but also visits the lower reaches of rivers and harbors. The bottlenose dolphin is the most common species of marine mammal to visit the Bay. They are most often seen in the lower Bay near Cape Charles and the James and Elizabeth rivers, but some venture as far north as Baltimore Harbor, the Chester River and Washington, D.C.


Image courtesy Minette Layne/Flickr

Beaver (Castor canadensis)

The beaver (Castor canadensis) is a large, brown, semi-aquatic mammal with a distinctive flattened, paddle-like tail. It lives in lakes, streams and forested wetlands throughout the Chesapeake Bay watershed. Beavers eat mostly tree bark and leaves and build lodges of sticks and mud on islands, river banks and shorelines. Within their lodges, beavers live in colonies that include an adult male and female and their young. To protect their lodges, beavers build dams across streams to flood the area and create deep, quiet ponds. These ponds also allow beavers to safely transport food and logs through the water. Ponds formed by beaver dams are important habitat for fish and waterfowl.

White-tailed deer

White Tailed Deer (Odocoileus virginianus)

The white tailed deer (Odocoileus virginianus) is found in forests, farms, parks and backyards throughout the Chesapeake Bay watershed. The white tailed deer gets its name from the white underside of its tail, which it will raise like a flag when alarmed.  They are remarkably good swimmers and agile runners capable of reaching speeds of 35 miles per hour and jumping 30 feet horizontally and 8.5 feet vertically. Deer have become overabundant in some areas because of their lack of predators, flexible feeding habits and ability to adapt to areas settled by humans.