----- "The Beaver in Ontario", by Ontario's Ministry of Natural Resources, 1976. [on paper, untyped] ----- "Canadian Wildlife Service: Hinterland Who's Who: Beaver", by Environment Canada, 1990. [on paper, untyped] ----- Excerpted from Compton's Interactive Encyclopedia Copyright (c) 1994, 1995, 1996 SoftKey Multimedia Inc. All Rights Reserved BEAVER. A mammal belonging to the order of rodents, or gnawing animals, the beaver has been recognized as a master engineer. By using teeth and paws, beavers construct lodges, storehouses, dams, and canals. The animal is also known for its aquatic life-style as well as for its beautiful fur. Kinds of Beavers The scientific name for the North American beaver is Castor canadensis. This animal once ranged over North America from Mexico to the Arctic regions. But its numbers are now reduced, and it is confined largely to northern wooded regions. The Old World beaver, Castor fiber, was once common throughout all of northern Europe, but it is now almost unknown except in parts of the Scandinavian peninsula, Germany, and Siberia. It is extinct in England. Subspecies include the Scandinavian, Elbe, Rhone, Polish, Ural, Mongolian, Canadian, Michigan, Newfoundland, Rio Grande, and Golden-bellied beavers. The beaver is the largest rodent in North America and the second largest in the world. Only the South American capybara is larger. An adult beaver may grow to be about 4 feet (1.3 meters) long, including its tail, and may weigh more than 60 pounds (27 kilograms). In prehistoric times giant beavers 7 1/2 feet (2.25 meters) long lived in North America. The spiral underground burrows that they dug eventually filled with debris that became fossilized. These masses of stone are called devil's corkscrews. Physical Characteristics The beaver has a thick body covered with a coat of long, reddish-brown outer hairs and soft, dense, brown underfur. This warm, waterproof coat allows the beaver to swim in icy water in the wintertime without discomfort. Most of the beaver's physical characteristics--the fur, toes, tail, ears, nose, and lips--are so constructed that the animal is well equipped for life in the water as well as on land. The toes on the beaver's large hind feet are webbed for swimming. The second toe on each hind foot ends in a double claw with which the animal combs its fur. The front feet are small and handlike and are used for picking up and carrying various objects. Beavers walk with their toes pointed inward. The tail is shaped like a paddle, broad and flat, and is covered with scaly skin. The tail serves as a prop when the beaver sits upright and as a rudder and scull when it swims. As a danger signal to other beavers, though they can vocalize, the normally placid animal makes a loud noise by slapping its tail on the water's surface. The beaver's facial features also allow for its aquatic life-style. The short, thick head has small rounded ears and a nose which are equipped with valves that close when the animal swims underwater. A beaver may remain submerged for up to 15 minutes. The animal carries objects underwater in its mouth by closing loose lips behind prominent front teeth, thus keeping water out of its mouth. Like other rodents, the beaver has well-developed front teeth. These teeth have a very hard layer on the front surface and a softer backing. Since this softer part wears away quickly, it leaves the thin chisel edge of the front layer exposed. The animal's teeth are always growing to make up for wear. The beaver has a total of 20 teeth. Life Cycle Beavers are social animals; they live in colonies and work together. The life span of the animal may be as long as 19 years. A beaver begins its life in a litter of from two to eight young, or kits. Four is the usual number. They are born in the spring, about four months after conception. A mother will sometimes raise not only her own offspring, but also the young of another female that has died. Newborn kits weigh from 8 to 24 ounces (225 to 680 grams) and are about 15 inches (38 centimeters) long, with tails that measure 3 1/2 inches (9 centimeters). Their eyes are open at birth. They are out learning to swim when they are only a month old, and they are weaned by six months. A family usually consists of a mature pair of beavers and two sets of offspring. A female first breeds when it is about 2 1/2 years old. The young stay with their mother into their second year, when they leave or are driven out before the mother gives birth to a new litter. By their third summer the young beavers are mature and ready to mate. They usually mate for life. A mated pair locates a fairly deep, slow-moving stream. They dig a burrow into the bank, starting below the surface of the water and slanting upward to a small room above the high-water mark. This is only a temporary residence in which the first litter will be born in the spring. Not until the following autumn does the couple set about building their permanent home--the lodge. Beavers live most of their lives in or near water. They settle along banks of streams, rivers, and lakes bordered by timberland. Large beaver populations have been credited with reducing flooding because of the dams they build across streams. On the other hand, they may also cause the flooding of roads and woodlands because of the reservoirs of water that build up behind the dams. Constant flooding can also damage valuable timber and block routes of migrating salmon. The reservoirs created by the dams are places where the beavers feel secure. It is in these artificially created ponds that beavers build their lodges and storehouses. The adult beavers select a narrow, shallow site in the water as a place to build a dam. They gnaw down a number of aspen, birch, or willow saplings. These they drag to the site and bury in mud with the butt ends pointing upstream. Into this foundation the beavers fit and pile more saplings, adding mud and stones until a strong barrier is completed. This structure allows enough seepage or overflow to keep the water in the reservoir fresh. Beaver dams come in all shapes and sizes. Normally a family of beavers can build a dam 35 feet (10 meters) long in about a week. Some dams more than 1,000 feet (300 meters) long have been found, but these are the work of generations of beavers. Lodges and Canals Beavers live in a structure called a lodge. The lodge is built in the riverbank or in the pond created by the dam. From a distance, the lodge resembles a heap of tree branches and mud. It consists of a platform of carefully interlaced branches held together by clay and dead leaves. When the platform has been built up a few inches above the water, the beavers fashion a dome-shaped roof over it. Before the coming of winter, the entire structure, which may enclose a room more than 5 feet (1.5 meters) high, must be plastered with mud. Entrances to the beaver lodge often open underwater, so that the animals may pass in and out below the winter ice. There are at least two, and up to five, such entrances. A steep and narrow entrance is used by the beavers for entry and exit. Another entrance is used for the transportation of wood for winter food. These underwater entrances help protect the beavers from attacks by predators which include, in North America, the wolverine, the lynx, and the wolf. Beavers move awkwardly on land; they prefer to swim. When they live in flat areas they sometimes build canals. These canals allow the beavers to more easily transport the logs that are too heavy to drag overland. A canal may measure more than 1,000 feet (300 meters) in length and from 2 to 3 feet (60 to 90 centimeters) in width. Food Supply When construction on dams, lodges, and canals is finished, the beavers gnaw whole groves of trees and sink the wood in the pond near their lodge. This collection forms the underwater winter storehouse. Their diet consists primarily of fresh green bark and wood such as poplar, willow, and birch. In the summer they also eat water plants, berries, swampwood, and fruit. Beavers do most of their building and food gathering at night. After an autumn of toil, beavers spend the winter resting. They swim out of their warm, dry lodges only to pluck a twig or branch from the storehouse. Commercial Value Although once plentiful throughout the wooded parts of the Northern Hemisphere, beavers had become an endangered species by the mid-19th century. They have been hunted for their fur, their tails, and their musk glands. Both sexes possess scent glands at the rear of the body that produce a liquid called castoreum, which is used in perfumes. It was also a popular medicine in the Middle Ages, apparently used to heal ailments ranging from headaches to dropsy. The healing ability of castoreum comes from its salicylic acid--a basic ingredient of aspirin--which the beaver acquires by eating willow bark. (Salicylic acid, a white crystalline substance (C6H4-OH-COOH) used in medicines, flavoring agents, and dyes; chiefly used, millions of pounds annually, in preparation of aspirin.) Common animal fixatives that increase the lasting qualities of perfumes include ambergris from the sperm whale, castor from the beaver, civet from the civet cat, and musk from the musk deer. The beaver has in the past been hunted for its scaly tail, which was considered a culinary delicacy. Beaver flesh in general was highly esteemed during the Middle Ages. It is the quest for the beautiful pelt that has most drastically reduced the beaver population. The soft, thick underfur of the beaver, which is at its best in late winter and spring, has long been highly valued. During the 17th, 18th, and early 19th centuries, beaver skins, made into caps and capes, were a staple of the world's fur trade. In fact, much of the exploration of North America, beginning early in the 1600s and continuing through the early 19th century, was prompted by the search for beaver fur. At one time beaver pelts were a medium of exchange. Beaver populations have been diminishing for centuries, possibly because of various natural causes as well as trapping. Almost too late, conservation laws were passed throughout the world, and the beaver was saved and was resettled in some areas where it had once been common. The beaver population in Russia and in North America has recovered to the extent that bans on hunting imposed earlier in the 20th century have been slightly modified. ----- http://ngp.ngpc.state.ne.us/wildlife/critters.html DESCRIPTION The beaver is North America's largest rodent. Adults may be 4 feet long and weigh over 60 pounds. A beaver is easy to identify because of its large size, its distinctive webbed hind feet and its large flat tail that resembles the end of a canoe paddle. The tail is nearly hairless and is a dull-black color. The "splat" that the tail makes when slapped on the water is one of the most distinctive of nature's sounds. The beaver's body fur is dark brown on its back and sides, and a light brown on its chest and belly. Its front feet are short and have heavy claws, and possess good dexterity for feeding, grooming, digging and lodge construction. Its hind legs are large and have fully webbed feet which propel it through the water when it is swimming. Like the muskrat's, the beaver's fur is virtually waterproof, and provides the protection and buoyancy necessary for the animal's extended underwater activities. The beaver's eyes are small in proportion to its body size, allowing moderate vision both under and above water. It has well-developed senses of smell and hearing, and its nose and ears have valvular processes which close tightly under water. There is a similar valvular process in its mouth behind the incisor teeth, which allows the beaver to gnaw while underwater. The beaver also possesses a specialized digestive system to help it digest tree bark, and a special respiratory adaptation which gives it the capability to remain submerged for nearly 20 minutes. These specialized physiological and morphological adaptations serve both positive and negative functions; they have made the beaver well suited for a specific environment, but have also restricted it to very narrow habitat tolerances. The beaver has two chisel-like incisors in its upper and lower jaws that grow constantly and are very effective tree cutting tools. These teeth are both self-sharpening and ever-growing, which means the beaver must use them continually to maintain their proper length and sharpness. Distribution and abundance In the early and mid 1870s, beavers ranged over most of North America, but excessive commercial trapping and human encroachment on its habitat resulted in the beaver being nearly wiped out in the eastern and the southern parts of the country. Habitat and home Beavers are found along streamcourses and rivers, small lakes and marshes. A beaver may dig a tunnel and form a den in a high stream bank or river bank, but in the standing water of lakes, marshes and backwaters, they most often pile tree limbs and other debris together, making a large, bulky, dome-shaped lodge. Beaver lodges are large structures constructed of wood and mud with at least one exit in deep water. Lodges contain a large bark-lined, above-water chamber which serves as the colony's "activity center." Although lodges are the most visible den sites, bank burrows are by far the most common denning structure in Nebraska. Burrows are usually dug from six to 20 feet into the bank before an above-water chamber is excavated and lined with fresh, shredded bark. On rivers like the Platte, where sandy soil prevents normal excavation, beavers will use the structural support of trees or shrub root systems to construct or maintain a den and burrow system. Over time, beavers will reinforce bank dens with sticks and mud, forming conical lodges called "half houses" at the water's edge. Habits The engineering skills possessed by beavers are well known. They are particularly adept at building dams, and may construct them across narrow, flowing waters, such as shallow streams and the channels of larger rivers. When a beaver cuts a tree, he usually-starts by gnawing a notch at an easy-to-reach height, then goes to the opposite side of the tree and gnaws another a few inches below the first. He continues chewing the bark and wood away from between the two notches until the tree falls. The only way the beaver can control where the tree falls is by the position of the notches he chews in the tree's trunk. In addition to building the dam and lodge, beavers often form waterways so they can float food and building materials from one area to another. Foods Beavers are primarily bark-eaters, and ingest the bark of young twigs, and new growth of wood found between the outer bark and the wood of tree branches and trunks. In spring and fall, about half of the beaver's food is made up of woody vegetation. In summer it eats little woody vegetation, but in winter it feeds on it almost exclusively. It also eats corn and other row crops when they are available, as well as various water plants. As fall approaches, the beaver begins to actively cut trees and shrubs for the colony's food cache. The quantity, quality and availability of this under-ice food supply will determine the condition and survival of the colony. Reproduction Beavers reproduce once a year, with mating activity beginning in January when rivers and wetlands are covered with ice. A 107 to 110 day gestation period follows, with an average of three to four young usually born in May. At birth the kits (young beavers) are fully furred, have their eyes open and incisor teeth visible. Kits are seldom seen until they are about one month old, though they are able to swim at birth, and are capable of being weaned in six to eight weeks. Although weaned within three months, the young usually remain with the family unit or colony for up to two years before leaving to establish a colony of their own. Typically, these two-year-olds will disperse, pair, establish territories, and raise their first litters at three years of age. However, under favorable conditions, they will produce their first litters at two years of age. The average lifespan of a beaver in the wild is three to four years. However, it is not uncommon to find eight-year-olds and rare individuals may reach or exceed 15 years of age. Importance The huge market for beaver felt was one of the main incentives that prompted the exploration and settlement of the west. Today beavers have both positive and negative economic values. The positive values center on the income generated by the harvest of beaver for their meat and fur, and the related recreational value. From 1942-86, nearly 400,000 beavers were taken by fur harvesters in Nebraska. Harvest totals from 1981-89 indicate an average annual harvest of 14,850 beavers valued at $255,000. Beavers are also important in the management of river and wetland habitats. Their construction of dams and the subsequent formation of pools create habitat for a large number of highly beneficial wildlife species. Negative impacts from beavers center on damage to trees and depredation to farm crops by cutting or flooding. Their burrowing activity can also cause shoreline erosion and structural damage to farm ponds, stock dams and dikes. These negative impacts are minimized through population regulation. ----- [ASCII art] ___ .=" "=._.---. ." c ' Y'`p / \ `\ w_/ | ) / / ______| /__-\ \_=.\ (_____/'`------)))`=-'"`'" d8= Your pet beaver is wearing goggles and a hard hat : = Beaver smiley (:= User is a beaver ,---. ,"XXXXX", "XXXXXXX" ()---() ".XXXXX," | o o |---`---' ( ^ ) | `U"U'| |--| |' /_/ /_/ _,--._ / \--. __Y \ (='_) (__|__Y_____/ " ----- [Dejanews] I've had to clean up after beavers, too. Their little elongated turds float in little log-rafts; must be all that wood. I've even held a baby one, and even at such a young age the tail was scaled. Their anal and urogenital orifices open into a common cloaca, too. -- Beavers (Castor canadensis) have been implicated in waterborne transmission of Giardia (see Wilson et al., (1986) Waterborne giardiasis outbreak - Alberta. Canada Diseases Weekly Report 8-20, 97-98) but Erlandsen et al. ((1988) Cross-species transmission of Giardia spp.: Inoculation of beavers and muskrats with cysts of human, beaver, mouse and muskrat origin. App. Envr. Microbiol. 54: 2777-2785) demonstrated that there is evidence for cross-species transmission. It is likely that Giardia can exist in a wide variety of mammalian hosts. As to species differences, there is Giardia lamblia, Giardia muris, Giardia agilis, Giardia psittaci, Giardia microtus, G. ondatrae, and G. ardae.... I don't know if the other species are known to infect human hosts. -- Your local hardware store may carry humane traps that will allow you to harvest them without damaging their fur or causing them an agonizing and prolonged death. Once in the trap, you can kill them with a point-blank shot to the head which will not damage the fur significantly and is a humane method - don't even think of hauling them out of a live trap for clubbing; those large teeth they have that do so much damage to your trees can do even more damage to you if you try to lay hands on a live one. Don't waste the meat - it is delicious, greasy, somewhat like pork and very tasty indeed. Remove the scent glands under the legs before processing out the meat. You can treat them like rabbits in terms of how you cut them up, though they are considerably larger and in my opinion tastier. The beaver tail can be roasted over an open fire to blister off the scaly skin, then fried; treat it as you would fatty bacon, and do *not* eat more than a small serving at a time, or you can get a seriously upset stomach from all the grease. A good recipe for the haunch is to drape the tail over it to keep it moist and well larded. Beaver is a dark meat that is best steam-roasted or fried in its own plentiful tail grease if you aren't watching the calories any. Some good accompaniments are mashed sweet potatoes with orange juice, boiled sheep sorrel or clover, and anything else you can think of that's a little tangy. It is also very good indeed in chili with plenty of stewed tomatoes. If you can get your hands on a good red wine, especially a smoky, earthy Syrah or Cote-du-Rhones, you have yourself a done dinner. If for whatever reason you're still squeamish about the matter, any little tree chewers you wanted to ship over here would find an honorable final resting place beneath mounds of steaming sweet potatoes on a comfortable bed of sorrel. -- Taos Beaver Tail Roast Ingredients 1 or 2 beaver tails salt and pepper to taste Directions Broil tails over hot fire or under broiler until rough hide peels off easily. Roast tail meat in moderate oven until fork tender. Great served with refried beans or garbanzo soup. ----- http://www.geocities.com/Yosemite/Trails/4060/Beaver.htm length: 44 - 70in. weight: 26 - 60 (lbs.) colony size: 1 - 8 colonies per square mile, usually 4 - 8 beaver per colony description: Largest rodent, brownish-black fur, large flat oval shaped tail coveredwith soft black scales. Other color variations: yellowish-brown, black, and albino The beaver has made quite a comeback in Pennsylvania. They were extirpated from the state in 1912 due to the extensive logging and trapping dating from the colonial times to the early part of this century. The pelt of this animal was partly responsible for the expansion of the United States. However, they were reintroduced in 1917 and thanks to proper wildlife management are now becoming quite numerous. They can be found along rivers, streams, ponds and lakes where there is small stands of trees. There they will build a lodge varying from 5 - 6 feet high and some 20 - 30 feet in diameter along with a dam or dams which can vary greatly in size and stretch for more than a half mile. The lodges have an inner chamber just above the water line with underwater entrances to where the beavers live. Not all beavers construct lodges and may burrow into the sides of river banks "bank beaver". Beavers like to eat bark, twigs, leaves and roots from woody plants by the water. Aspen, birch, willow, maple, poplar and alder are some of the more sought after trees as these also make good building material for their dams and lodges. They will also eat rushes, grasses and sedges during the summer months. They cache their food for the winter by partially burying green branches and logs on the bottom of the pond surrounding their lodge. These caches may be large enough to reach the surface of the pond. Beavers are very territorial and mark their territory by creating mud patties and smearing them with castoreum (castor mounds) which is produced from two large glands at the base of the tail. They also slap the water with their tail to warn intruders or to alert the colony to potential danger. While female beavers may mate for life, male beavers do not neccessarily follow suit. Kits are born in May or June following a gestation period of about 107 days. Kits usually stay with the mother for two years and are then driven off or disperse on their own. The beaver does not have very many natural predators. Occasionally a bear or coyote will attack an adult and mink, hawks and owls will sometimes take the smaller kits. Beavers can develop rabies and carry Giardia. Suggested trap sizes: If using a leghold trap use a large size No. 3 or 4 (in Pennsylvania the jaw spread can be no larger than 6 1/2 inches), No. 220 or 330 Conibear for underwater or under ice sets. Suggested sets: Castor mound set, bait pen set, platform sets. ----- http://www.nationaltrappers.com/Beaver.html The beaver is the largest North American rodent. A common furbearer, the beaver inhabits waterways of every North American state and Canadian Province. A unique paddle shaped tail distinguishes the species and self-sharpening teeth allow beavers to mow down sizable trees. Beaver often alter the landscape with the construction of dams, canals and lodges. Beaver are territorial as long as the habitat will support family groups called "colonies". Beaver are powerful animals both on land and in the water. Description Beaver continue to grow in size throughout life, and weights in excess of 60 or 70 pounds do occur when foods are abundant and accessible during the entire year. Unlike many other species, females are as large as males of the same age, and they sometimes are larger. A paddle shaped, leathery tail, positively identifies the species. An adult's tail is usually about 10 inches long, and 5 or 6 inches wide, with a thickness of 1/2 inch in the middle. The hind feet of beaver are fully webbed, and large. These feet often measure 6 inches in length, and the spread of the toes is equal to or greater than the length as the beaver swims. Five toes with strong nails are found on the hind feet, including unique split toenail on one toe which serves the beaver as a comb for grooming. The front feet seem small in contrast to the hind feet. These feet measure 2 1/2 to 3 inches in length and are not webbed at all. Beaver normally swim with their front feet held against their chest, and the large webbed hind feet provide the propulsion with the tail acting as a rudder. Guard hairs in beaver fur are 2 inches in length, overlaying a soft and dense underfur about an inch deep. Colors vary from section to section, and from blonde colors to nearly black. Both male and female beaver have large glands, called castors, beneath the skin on the lower bellies. These glands produce an oil which the beaver combs into its fur to waterproof it. This oil is also deposited by the beaver at selected locations as territorial markers or mating attractants in the spring of the year. Beaver have transparent eyelids which cover the eyes as the beaver submerges, enabling the beaver to see well when submerged as the eyeball is protected from abrasive particles suspended in the water. The ears and nose of a beaver have valves that close as a beaver submerges, preventing the entry of water. Two upper and two lower incisor teeth dominate the front of a beaver's mouth. The upper incisors overlap the lower incisors, and friction from chewing causes the teeth to self-sharpen to chisel sharpness. Similar to birds and reptiles, beaver have a single lower body opening, known as a cloaca. This single opening serves the urinary and bowel tracts, the secreted oil from the castor glands, and covers the reproductive organs of both males and females. Reproduction Beaver usually live in family units consisting of the older mated pairs, young from the previous year, and young from the current season called kits. Breeding season takes place in late January or February in most states. Young from the previous year are about 22 months of age at this time and they are evicted from the colony to relocate and seek mates of their own. The gestation period of beaver is 107 days and the adult male and kits usually take up a temporary residence in a bank den while the new litter is being born in April, May or June. The birthing process may take several days, and 3 to 5 kits are a typical litter size. Beaver kits are fully furred when born, their eyes are open, and the incisor teeth are visable. Newborn beaver kits take to the water easily, and they might be swimming before they are one day old. Most adult beaver are monogamous, and stay with their mate throughout life. Habits Beaver require deep water for protection from their enemies, and they alter the landscape a great deal with dam building and flooding. Dams can be hundreds of feet in length, and vary in height from only a few feet to 7 or 8 feet, and even higher at times. Permanent lodges are often constructed by piling layer after layer of sticks into a large conical form above the waterline. Two or more underwater tunnels are then chewed up into the pile, and an inner chamber hollowed out to serve as a living quarters Finally the outside of the lodge is plastered with mud and rocks, except for the peak, which is left porous enough to allow an air exchange to the inner chamber. There are two levels to the chamber. One level is near the waterline near the "plunge holes", where the beaver shed water before climbing to the higher resting or nesting areas. In areas prone to flooding, or where strong currents may be present, beaver usually construct bank dens by digging tunnels from underwater up into banks. Bank dens often have two or more submerged entrances. Many times the beaver will construct a pile of sticks over the tops of the underground living chambers. These piles of sticks are sometimes called "caps". Shallow pockets are sometimes dug into banks near the waterline and these are known as "feed pockets". In northern areas, beaver construct "feed piles" by submerging large amounts of small trees and limbs to serve as a food source after ice prevents th beaver from activity above the ice. These feed piles are usually constructed close to the den as a convenience to the kit beaver, who do not normally travel far from the den itself. At times, solitary beaver will be found living alone. These beaver are known as "bachelors", whether they are male or fernale. Adult beaver mark out their territories in early spring by dragging up mud and debris from the bottom and depositing the debris in mounds along the shores, where they also deposit oil from their castor glands. These "castor mounds" often leave a reddish stain on the bank, and the odors are powerful enough for a human to easily detect. Beaver are very territorial, and territories seldom overlap. Generations of beaver may continuously inhabit a choice area, even building canals to help float food from inland cutting sites. If and when food supplies are exhausted, they do relocate to better area. Once beaver have determined to claim a territory, they are very difficult to dissuade. If the activities of the beaver flood roads or damage property, the beaver usually have to be removed to prevent reoccurring damages. Although beaver normally submerge for 3 or 4 minutes at a time, they are quite capable of holding their breath for 12 to 15 minutes. They exhale a little in spurts as they swim or work under water, and a large beaver is quite capable of traveling nearly 1/2 mile under the surface before it must surface for more air. Migrations of beaver usually occur with the breakiing up of ice in late winter or early spring as the 22 or 23 months old beaver are expelled just prior to birthing time for the new litter. These beaver may chose to go up or downstream. Although these beaver are capable of reproducing, they usually do not until the next season, after a mate and a new territory have been established. Most new colonies are established within a few miles of the home colony. Beaver are primarily vegetarians although an occasional beaver may eat a dead fish. Preferred foods include the bark of aspen, willow, cottonwood, and dogwood, and many other varieties of trees and shrubs. In early spring, beaver will often eat bark a twigs of evergreens. In season, beaver will also eat water lillies, leaves, grassses, roots, and a variety of crops including corn, wheat, oats, carrots, potatoes, apples, clovers, and alfalfa. 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 drinikng 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. At times, a bear can and will kill mature beaver. Juvenile beaver are vulnerable to coyotes, eagles, and large owls as well. Tularemia can be a devastating disease in beaver, wiping out entire populations when conditions are good for disease transmissions. Tularemia infects livers, and is usually fatal to beaver of all ages. A beaver is considered to be old at 12 years of age. ----- http://www.doe.ca/envcan/docs/beaver/beaver.html Distribution Beavers are found throughout Canada, north to the mouths of the Mackenzie and Coppermine rivers on the Arctic Ocean. Most common in forested areas, beavers also expand into unforested habitats where there are watercourses bordered by deciduous (broad-leaved) trees or shrubs. Thus, in western Canada, they are found along streams on the dry prairie. Even in the tundra, beavers occasionally colonize shrubby water edges where water is deep enough to allow for food storage and access to the den under the winter ice. In the rest of North America, the beaver's range extends throughout southwestern Alaska and most of the states south of the 49th parallel. The beaver has been exterminated in some states, and in practically all of its former range in northern Mexico. Physical characteristics The beaver is the largest rodent in North America and largest in the world except for the capybara of South America. An adult weighs from 16 to 32kg and, including its 30-cm tail, a large beaver may measure 1.3m long. Their ancestors were even larger. In the Pleistocene ice age - the era of the mastodons and mammoths - the giant beavers that inhabited the expanses of Eurasia and North America measured just under 3m in length including tail and probably weighed 360kg. Very compact and rotund, a beaver walking on land appears to have no neck at all; the round profile of its head merges into the round profile of its back. Because its legs are short, it is ungainly and slow on land. When frightened, it can travel quickly in an awkward, bounding gallop, but over a distance of a hundred or so metres a person can run a beaver down. Not so in the water. The beaver is a graceful, strong swimmer, both under water and on the surface, attaining speeds approaching 7km per hour if alarmed. It has many adaptations to its watery habitat. Its small beady eyes are able to see as well in the water as out of it thanks to a specialized transparent membrane that can be drawn over the eye for protection while diving. Its nostrils are small and can be closed for underwater swimming, and its ears too, can be closed under water. The beaver's tail has important uses both in the water and on land. The tail of a large beaver may be 30cm long, up to 18cm wide, and 4cm thick. It is covered with leathery scales and sparse, coarse hairs. In the water, the animal can use its tail as a four-way rudder. Although fat, the tail is flexible and muscular. When diving after being frightened, a beaver slaps the water with its tail, making a noise like a pistol shot, which warns all beavers in the vicinity that danger is near and perhaps serves to drive away potential predators. On land, the tail acts as a prop when the beaver is sitting or standing upright. It also serves as a counterbalance and support when the animal is walking on its hind legs while carrying building materials like mud, stones, or branches with its front paws. The beaver's hind feet are very large, with five long blunt-clawed toes which are fully webbed, for swimming. In the water, a beaver uses only its hind feed to propel itself, with occasional aid from its tail. Its forepaws are small, without webs, and the toes end in long sharp claws suited to digging. These delicate paws are very dextrous - almost like hands - and with them the beaver can hold and carry sticks, stones, and mud and perform a variety of complex construction tasks. The beaver also uses its paws to groom its coat. The second toe on each hind foot is double-clawed, the claws being hinged to come together like tiny pliers. These specialized claws on the hind feet along with the front claws are used for combing the fur. The beaver has several reasons to groom itself. The dark brown fur is very dense, consisting of a mat of fine underfur about 2cm long and an outer layer of heavy guard hairs 6 - 7cm long. Through constant preening and oiling this dense pelt is kept waterproof. Even after swimming under water for 6 or 7 minutes the beaver is not wet to the skin. Oil is obtained from two glands near the anus and, like preening, application of oil is done with both front and hind feet. Preening also removes dirt, straightens matted fur and removes mites and other insect parasites. Members of family groups spend considerable time preening each other. Finally, the animal has exceptional teeth. Its long, sharp, strong incisors grow continuously and are hardened with a dark orange enamel on the forward face. Consequently, as the upper and lower incisors are ground against each other, the outer tips of these teeth are maintained chisel-sharp. With them, a beaver is able to fell very large trees. The lips can be closed behind the incisors, permitting the beaver to gnaw on twigs while under water. Life history A beaver takes only one mate, which it keeps for life. One litter, averaging three or four kits, is born each year in May or June following a 100-day gestation period. Although kits are well-furred, have teeth already cut, and can see, walk, and swim when born, they generally don't move out of the lodge for at least one month. They become capable of reproducing at age two. The young stay with their parents until they are two and sometimes three years old. At that time they disperse in response to an innate urge to leave the home colony, and migrate along streams or across country until they find mates and suitable building sites, whereupon they establish their own dams and lodge. These dispersal migrations can vary from just a few kilometres up to 250km. With the first frosts of September and October, the tempo of beaver life speeds up as the animals harvest their winter food supply. Trees are cut down, gnawed into short lengths, and toted to the pond for underwater storage. All winter the beavers bring sticks from their underwater cache into the feeding chamber of the lodge to gnaw the succulent bark. They prefer trembling aspen, poplar, willow, and birch. They also swim out under the ice and retrieve the thick roots and stems of aquatic plants, such as pond lilies and cattail. During mild winters and during warm days in March and early April, adult beavers emerge from their dull aquatic world to feed on fresh woody stems along the shore. On such forays they often fall prey to hungry wolves. Beaver shift from a woody diet to a herbaceous diet as new growth appears in the spring. During summer, beaver will utilize grasses, herbs, leaves of woody plants, fruits, and aquatic plants. Each day, beaver alternate periods of activity and rest. They are most active from dawn to dusk. Mid-day generally finds them in the den, be it summer or winter. Although their aquatic habit offers excellent protection from predators, beavers are vulnerable in many ways. Beavers fall prey to wolves, coyotes, bears, lynx, and wolverine when foraging on shore or migrating overland. The river otter is able to enter the den via the water and kill the kits inside; however, an adult or subadult beaver always stays with the kit to offer protection. Sudden fluctuations in water levels can force beavers to leave their den and face danger on shore. At bay, beavers stand their ground and protect themselves. They face the aggressor, rear up on their hind legs, and loudly hiss or growl before lunging forward to deliver extremely damaging bites. They should not be closely approached when cornered on land. ----- http://www.oit.itd.umich.edu/bio/doc.cgi/Chordata/Mammalia/Rodentia/Castoridae/Castor_canadensis.ftl Geographic Range Nearctic: Beavers are found throughout North America except for the Southwest, and Mexico. (Frazier, 1996) Physical Characteristics Mass: 13. to 27 kg Beavers are primarily aquatic animals. They have waterproof, rich, glossy, brown fur, and large, black, webbed feet. Their powerful hind legs also increase their swimming ability. Beavers have the ability to close their noses and ears while swimmimg underwater, and they have a clear eyelid to protect their eyes from the water and debris. The tails are one of the defining characteristics of beavers. They are broad and flat with large, blackish scales. Another characteristic of beavers is their teeth. Like all rodents, beavers have large central incisors (front teeth) that are always growing. They must keep them trimmed by gnawing bark. (Hall and Kelson, 1959; Frazier, 1996; Sevilleta LTER, 1995) Natural History Food Habits Castor canadensis eat bark and cambium (the softer growing tissue under the bark of trees). Their favorites include willow, maple, poplar, beech, birch, alder, and aspen trees. They also eat water vegetation as well as buds and roots. Cellulose, which usually can not be digested by mammals, is a major component of their diet. Beavers have microorganisms in their cecum (a sac between the large and small intestine) that digest this material. In zoos, beavers are fed yams, lettuce, carrots and "rodent chow." (Hall and Kelson, 1959; Frazier, 1996; Sevilleta LTER, 1995) Reproduction Female Castor canadensis are sexually mature at 2.5 years old. They give birth to one litter of kits per year, usually between April and July. The gestation period is about 3 months. The litter usually consists of 4 kits, but up to 8 are possible. They are born with all of their fur, their eyes open, and their incisor teeth erupted. The young usually stay with their parents for 1-2 years and then leave to make their own homes. (Frazier, 1996; Sevilleta LTER, 1995) Behavior Beavers form monogamous pairs and usually live in family groups of up to 8 related individuals called colonies. The younger siblings stay with their parents for up to 2 years, helping with infant care, food collection, and dam building. Beaver families are territorial and defend against other families. In order to warn each other of danger, beavers slap their tails against the water, creating a powerful noise. Beavers are primarily nocturnal. They are only occasionally seen during the day. They usually wake at dusk. Castor canadensis travel good distances from their homes to find food. If they find a good source, they build canals to the food source as a way to float the food back to their lodges. Logs and twigs are stored underwater for winter feeding. Beavers build dams to slow down the flow of water in streams and rivers and then build stable lodges for shelter. The dams are engineered according to the speed of the water; in slow water the dam is built straight, but in fast water the dam is built with a curve in it. This provides stability so that the dam will not be washed away. The lodges are made of sticks, mud and rocks. In faster rivers and streams, beavers sometimes build lodges into the sides of banks. Some lodges are large enough to fit a human being inside of them. The actual living area is underwater so the temperature is considerably warmer inside the lodges than outside. Lodges can have several entrances that are usually underwater. (Hall and Kelson, 1959; Frazier, 1996; Sevilleta LTER, 1995; http://web.idirect.com/~hland/sh/an020.htm, 1996) Habitat Beavers live in streams, rivers, and lakes where trees are abundant. (Hall and Kelson, 1959; Frazier, 1996; Sevilleta LTER, 1995; http://web.idirect.com/~hland/sh/an020.htm, 1996) Biomes: temperate forest & rainforest, freshwater lake, freshwater rivers Conservation/Biodiversity Status: no special status. The conservation status differs with respect to source, but there have been significant threats to the survival of the beaver. Beavers have been hunted and trapped extensively in the past and by about 1900, the animals were almost gone in many of their original habitats. Pollution and habitat loss have also effected the survival of the beaver. In the last century, however, beavers have been successfully reintroduced to many of their former habitats. (Frazier, 1996; Sevilleta LTER, 1995) Economic Benefits for Humans Positive Beaver fur has been a significant trade item for the last century, creating large amounts of money for merchants. Beavers are incredibly beneficial to the environment. They are instrumental in creating habitats for many aquatic organisms, maintaining the water table at an appropriate level and controlling flooding and erosion, all by building dams. See the Sevilleta Long-Term Eocological Research Project (LTER)/ RKM and KVP-- University of New Mexico account on the web at http://sevilleta.unm.edu/animal/mammal/beaver.html for a more detailed explanation of the benefits of beavers in the environment. (Sevilleta LTER, 1995) Negative Although beavers are beneficial to the environment, they can destroy it also. Dams slow the flow of water in fast streams, changing the flora and fauna and sometimes creating silting. They may flood low-lying areas, sometimes causing extensive loss of timber. ----- [compiled from above] SIZE: Usually, an adult beaver weighs between 16 to 27 kilograms (35 to 60 lbs), and may weigh up to 32 kilos (70 lbs) Including its 30-cm tail, a beaver measures about 130 cm (51 inches) long, but may be anywhere between 115 and 175 centimetres (44 - 70 inches). BODY: With a thick, very compact and rotund, a beaver walking on land appears to have no neck at all; the round profile of its head merges into the round profile of its back. Because its legs are short, it is ungainly and slow on land. When frightened, it can travel quickly in an awkward, bounding gallop, but over a distance of a hundred or so metres a person can run a beaver down. FUR: The beaver's body is covered with a coat of long, reddish-brown outer hairs and soft, dense, brown underfur. The beaver's body fur is dark brown on its back and sides, and a light brown on its chest and belly. Guard hairs in beaver fur are 2 inches in length, overlaying a soft and dense underfur about an inch deep. Colors vary from section to section, and from blonde colors to nearly black. This warm, virtually waterproof coat allows the beaver to swim in icy water in the wintertime without discomfort, and provides the protection and buoyancy necessary for the animal's extended underwater activities. The beaver has several reasons to groom itself. The dark brown fur is very dense, consisting of a mat of fine underfur about 2cm long and an outer layer of heavy guard hairs 6 - 7cm long. Through constant preening and oiling this dense pelt is kept waterproof. Even after swimming under water for 6 or 7 minutes the beaver is not wet to the skin. Oil is obtained from two glands (castors) near the anus and, like preening, application of oil is done with both front and hind feet. Preening also removes dirt, straightens matted fur and removes mites and other insect parasites. FEET: Its hind legs are large. Beavers walk with their toes pointed inward. The toes on the beaver's large hind feet are fully webbed, and propel it through the water when it is swimming. These feet often measure 6 inches in length, and the spread of the toes is equal to or greater than the length as the beaver swims. Five long blunt-clawed toes with strong nails are found on the hind feet The second toe on each hind foot is double-clawed, the claws being hinged to come together like tiny pliers. These specialized claws on the hind feet along with the front claws are used for combing the fur. In the water, a beaver uses only its hind feed to propel itself, with occasional aid from its tail. Front Paws: Its front feet are short, small, without webs, and have heavy claws, and possess good dexterity for feeding, grooming, digging and lodge construction. The front feet seem small in contrast to the hind feet. These feet measure 2 1/2 to 3 inches in length and are not webbed at all. Beaver normally swim with their front feet held against their chest. Its forepaws are small, without webs, and the toes end in long sharp claws suited to digging. These delicate paws are very dextrous - almost like hands - and with them the beaver can hold and carry sticks, stones, and mud and perform a variety of complex construction tasks. HEAD: The beaver's facial features also allow for its aquatic life-style. A beaver may remain submerged for up to 15 minutes. The animal carries objects underwater in its mouth by closing loose lips behind prominent front teeth, thus keeping water out of its mouth. It has well-developed senses of smell and hearing. Eyes: The beaver's eyes are small in proportion to its body size, allowing moderate vision both under and above water. Beaver have transparent eyelids which cover the eyes as the beaver submerges, enabling the beaver to see well when submerged as the eyeball is protected from abrasive particles suspended in the water. It has many adaptations to its watery habitat. Its small beady eyes are able to see as well in the water as out of it thanks to a specialized transparent membrane that can be drawn over the eye for protection while diving. Ears: The short, thick head has small rounded ears which are equipped with valves that close when the animal swims underwater, preventing the entry of water. Nose: The head has a nose which is equipped with valves that close when the animal swims underwater. MOUTH: There is a valvular process in its mouth behind the incisor teeth, which allows the beaver to gnaw while underwater. The lips can be closed behind the incisors, permitting the beaver to gnaw on twigs while under water. TEETH: The beaver has a total of 20 teeth. Like other rodents, the beaver has well-developed incisors. These teeth have a very hard layer on the front surface and a softer backing, and the upper pair of incisors overlap the lower pair, and friction from chewing wears away the softer part, leaving the thin chisel edge of the front layer's dark orange enamel exposed. The animal's teeth are always growing to make up for wear. With them, a beaver is able to fell very large trees very effectively. The beaver must use them continually by gnawing bark to maintain their proper length and sharpness. TAIL: The tail is oval, shaped like a paddle, broad and flat. It is leathery, covered with dull-black scaly skin and sparse, coarse hairs. Although fat, the tail is flexible and muscular. An adult's tail is usually about 25 to 30 cm (10 - 12 inches) long, and 13 - 18 cm (5 - 7 inches) wide, with a thickness of 2 - 4 cm (.5 - 1.5 inches) in the middle. In the water, the animal can use its tail as a four-way rudder and scull. On land, the tail acts as a prop when the beaver is sitting or standing upright. It also serves as a counterbalance and support when the animal is walking on its hind legs while carrying building materials like mud, stones, or branches with its front paws. When diving after being frightened, a beaver slaps the water with its tail, making a noise like a pistol shot, which warns all beavers in the vicinity that danger is near and perhaps serves to drive away potential predators. GUTS: The beaver possesses a specialized digestive system to help it digest tree bark, and a special respiratory adaptation which gives it the capability to remain submerged for nearly 20 minutes. Similar to birds and reptiles, beaver have a single lower body opening, known as a cloaca. This single opening serves the urinary and bowel tracts, the secreted oil from the castor glands, and covers the reproductive organs of both males and females. CASTORS: Both male and female beaver have large glands, called castors, beneath the skin on the lower bellies. These glands produce an oil which the beaver combs into its fur to waterproof it. This oil is also deposited by the beaver at selected locations as territorial markers or mating attractants in the spring of the year. -----