AMERICAN BEAVER (Castor)

Beaver is a medium-sized semiaquatic rodent.

Wildlife Stats:

Color: Various shades of brown
Size: Up to 36 inches in length, Up to 71 pounds in weight
Habitat: Found throughout NJ

Habits:

  • Muskrats eat a wide variety of plants, including cattails, sedges, bulrush, arrowhead, water lilies, pondweed, and ferns. They also eat alfalfa, clover, corn, and other crops if muskrats find them in their territories.
  • Although muskrats will eat shellfish, snails, fish, frogs, and salamanders, such animal foods are a small part of their diet, and are generally consumed when plant foods are scarce.
  • Muskrats normally feed within 150 feet of their main dwellings; however, they will travel much farther in search of food.
  • When muskrats become too numerous, an “eat-out” can occur where nearly all the available food is eaten. The eat-out area becomes virtually uninhabitable for muskrats, and only a few animals may be found where dozens or more once were.

Habitat:

  • Beavers eat the leaves, inner bark, and twigs of aspen (a favorite food), alder, birch, cottonwood, willow, and other deciduous trees. Beavers also eat shrubs, ferns, aquatic plants, grasses, and crops, including corn and beans.
  • Coniferous trees, such as fir and pine, are eaten occasionally; more often, beavers will girdle and kill these trees to encourage the growth of preferred food plants, or use them as dam building material.
  • Beavers have large, sharp, upper and lower incisors, which are used to cut trees and peel bark while eating. The incisors grow their entire lives but are worn down by grinding them together, tree cutting, and feeding. (Fig.1)
  • Fermentation by special intestinal microorganisms allows beavers to digest 30 percent of the cellulose they ingest.
  • When the surface of the water is frozen, beavers eat bark and stems from a food “cache” (a safe storage place) they have anchored to the bottom of the waterway for winter use. They also swim out under the ice and retrieve the thick roots and stems of aquatic plants, such as pond lilies and cattails.

Threats:

Although beavers are important contributors to natural aquatic systems, their dam building can cause severe flooding, that damages roadway, and buildings.

Beavers can be infected with the bacterial disease tularemia. Tularemia is fatal to animals and is transmitted to them by ticks, biting flies, and via contaminated water. Animals with this disease may be sluggish, unable to run when disturbed or appear tame.

Tularemia may be transmitted to humans if they drink contaminated water, eat undercooked, infected meat, or allow an open cut to contact an infected animal. The most common source of tularemia for humans is to be cut or nicked by a knife when skinning or gutting an infected animal. Humans can also get this disease via a tick bite, a biting fly, ingestion of contaminated water, or by inhaling dust from soil contaminated with the bacteria.

A human who contracts tularemia commonly has a high temperature, headache, body ache, nausea, and sweats. A mild case may be confused with the flu and ignored. Humans can be easily treated with antibiotics.

Beavers are among the few animals that regularly defecate in water, and their droppings (like those of humans and other mammals) may cause a flu-like infection when contaminated water is ingested. The technical name for this illness is “giardiasis.” It is more commonly referred to as “giardia”—derived from giardia, the single-cell protozoan that causes the disease. Another popular term, “beaver fever,” may be a misnomer. It has never been demonstrated that the type of giardia beavers carry causes giardiasis in humans.

Prevention:

One of the most effective measures to deter beavers is to install culvert fencing. The culvert fencing makes damning the water extremely difficult.

Control:

Beavers are considered a fur-bearing animal and special permits are needed to trap them outside of trapping season.

Spillway

Beaver Dam

Beaver Dam