General Beaver usually alter the habitat a great deal with the building of dams, and the resulting flooding of lowlands. The deeper water behind dams creates a better habitat for muskrats, and a variety of other wildlife species such as fish and waterfowl. Mink and otter hunt regularly around beaver dams. These locations provide suitable denning sites as well for these furbearers. Dam building on trout streams can have an adverse effect on trout survival by slowing the water and allowing it to warm to temperatures higher than the trout can tolerate.
Dams also serve as barriers to migrating trout and salmon.
At times, beaver cause significant amount of property damage by cutting trees, and flooding large areas also killing the timber. Culvert plugging is common, and often causes roads to flood and to wash out, Beaver are also host to an internal parasite, giardiasis. Water reservoirs inhabited by beaver can and do become contaminated by the giardiasis cysts, which are too small to be filtered out of the drinking water. These cysts hatch in the small intestines of people who drink the contaminated water resulting in diarrhea, nausea, and stomach aches. Serious beaver predators include mountain lions, wolves, lynx and bobcats.