American Beaver

## Description

The American beaver is a semiaquatic animal native to North America. Its coat is repellent with a shiny, rich, blackish-brown to russet color. The underlayer of hair is tighter and more protective than the outer layer. Ears usually have an amber color, being round and short. When a beaver walks, the front part of its body is closer to the ground than the rear, due to its front legs being shorter than its hind legs.

## Distribution

Before their near-extirpation by trapping in North America, these animals lived from south of the arctic tundra to the deserts, mountains of northern Mexico, and from the Atlantic to the Pacific Oceans. They are widely distributed in boreal and temperate ecoregions, where populations are rebounding from historic over-exploitation. Recently, American beavers have been observed colonizing arctic tundra, likely as a result of climate-induced increases in riparian shrubs.

## Behavior

American beavers are highly sociable animals. They make up colonies - family groups of about 8 individuals in each one – and live within a hierarchy. Beavers are very territorial, protecting their home range from other beaver colonies. The period of their highest activity is the nighttime, though sometimes they can be seen in the daytime, more frequently in the twilight. In search of food, beavers are ready to pass long distances. When the source of food is found, a beaver opens water canals to it in order to transport the food across the water to its lodge. Beavers also pile up branches and sticks under the water as winter supply. In areas of fast water flow beavers construct dams to slow down the stream. Their lodges are very firm to be able to serve as shelters. Beavers construct dams, depending on the speed of the water stream: if the stream is strong, dams are built in a way so as to withstand the pressure of water flow and not be washed away.

## Diet

American beavers are herbivores and lignivores; they feed on the bark of trees and cambium - the inner layer, which is under the bark. The favorite trees include willows, aspen trees, alders, maples, and birches. Along with these, beavers feed upon aquatic plants meanwhile not missing roots and buds.

## Reproduction

American beavers are monogamous, meaning that they mate once in a lifetime. A lodge serves as a home for a family - a couple and their young (until reaching the age of 1 year). The mating period takes place during winter (January-March) in the north and in late autumn (November-December) - in southern regions. Gestation lasts 3 months, after which 3-6 babies are born. The young are born with dense coat and open eyes. They begin swimming on the very first day of their lives. A few days later their parents take the babies to travel around the home range and explore the world. As a general rule, the young are weaned no later than 2 weeks while sometimes it can take up to 3 months. Parents look after them until they are at least 2 years old after which young leave. Both males and females of American beaver become reproductively mature at 3 years of age.

## Population

### Threats

Beavers attract hunters for their pelts. On the other hand, near human settlements, beavers are killed for building dams and destroying trees, thus disturbing human life. In addition, beavers are susceptible to tularemia – an animal disease, common in North America. And finally, a human disturbance may put beavers in real danger: people kill them for pelts and persecute them from their habitat, not speaking about pollution, which promotes wound infection.

### Number

The IUCN Red List and other sources don’t provide the number of the American beaver total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.

### Eoclogical niche

The American beaver lives in marshy areas which slow down water streams in a case of a flood. The beaver hinders soil erosion and promotes water level rise. Sludge occurs upstream of the dikes thus putting toxins out of action. Ponds start to grow from water, supported by dams, after which lilies appear. And then, when the lodges are left by beavers, eventually the dams start decaying, giving way to meadows.

## Fun Facts

Teeth of beavers never stop growing, so they gnaw on trees in order to prevent teeth from becoming too long.

Beavers use their tails for swimming as well as flapping the water in order to scare predators away.

The American beaver is announced to be the national animal of Canada.

Beavers have transparent eyelids, serving as underwater glasses and helping them see clearly under the water.

Beavers withstand cold temperatures easily. Moreover, they are active during the cold season and even manage to maintain order in ponds around their lodges.

Regular lodges of beavers have 2 dens: the first one is to dry off after coming out of water; the second one, a dryer den, is used for beavers’ families to spend their time.

Cases are known, when beavers’ and muskrats’ families share one lodge together.