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Beavers
Beavers (genus ''Castor'') are large, semiaquatic rodents of the Northern Hemisphere. There are two existing species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers are the second-largest living rodents, after capybaras, weighing up to . They have stout bodies with large heads, long chisel-like incisors, brown or gray fur, hand-like front feet, webbed back feet, and tails that are flat and scaly. The two species differ in skull and tail shape and fur color. Beavers can be found in a number of freshwater habitats, such as rivers, streams, lakes and ponds. They are herbivorous, consuming tree bark, aquatic plants, grasses and sedges. Beavers build dams and lodges using tree branches, vegetation, rocks and mud; they chew down trees for building material. Dams restrict water flow, forming ponds, and lodges (usually built in ponds) serve as shelters. Their infrastructure creates wetlands used by many other species, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Beaver
The North American beaver (''Castor canadensis'') is one of two Extant taxon, extant beaver species, along with the Eurasian beaver (''Castor fiber''). It is native to North America and has been introduced in South America (Patagonia) and Europe (primarily Finland and Karelia). The North American beaver is one of the national symbols of Canada and the official state mammal of Oregon and New York (state), New York. North American (Canadian) beavers are widespread across the continental United States, Canada, southern Alaska, and some parts of northern Mexico. In Canada and the United States, the North American beaver is often referred to simply as "beaver", although this can cause some confusion because another distantly related rodent, ''Aplodontia rufa'', is often called the "mountain beaver". Other vernacular names, including American beaver and Canadian beaver, distinguish this species from the other Extant taxon, extant beaver species, ''Eurasian beaver, Castor fiber'', which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eurasian Beaver
The Eurasian beaver (''Castor fiber'') or European beaver is a species of beaver widespread across Eurasia, with a rapidly increasing population of at least 1.5 million in 2020. The Eurasian beaver was hunted to near-extinction for both its fur and castoreum, with only about 1,200 beavers in eight Relict (biology), relict populations from France to Mongolia in the early 20th century. It has since been Eurasian beaver reintroduction, reintroduced into much of its former range and now lives from Western Europe, Western, Southern Europe, Southern, Central Europe, Central and Eastern Europe, Scandinavia, Russia through China and Mongolia, with about half the population in Russia. It is listed as least concern on the IUCN Red List. Taxonomy ''Castor fiber'' was the scientific name used by Carl Linnaeus in 1758, who described the beaver in his work ''Systema Naturae''. Between 1792 and 1997, several Eurasian beaver zoological specimens were described and proposed as subspecies, includ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beaver Dam
A beaver dam or beaver impoundment is a dam built by beavers; it creates a pond which protects against predators such as coyotes, alligators, cougars, foxes, eagles, wolves and bears, and holds their food during winter. These structures modify the natural environment in such a way that the overall ecosystem builds upon the change, making beavers a keystone species and ecosystem engineers. They build prolifically at night, carrying mud with their forepaws and timber between their teeth. Construction A minimum water level of is required to keep the underwater entrance to beaver lodges from being blocked by ice during the winter. In lakes, rivers and large streams with deep enough water, beavers may not build dams, and live in bank burrows and lodges. Beavers start construction by diverting the stream to lessen the water's flow pressure. Branches and logs are then driven into the mud of the stream bed to form a base. Then sticks, bark (from deciduous trees), rocks, mud, grass, leav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anal Gland
The anal glands or anal sacs are small glands near the anus in many mammals. They are situated in between the external anal sphincter muscle and internal anal sphincter muscle. In non-human mammals, the secretions of the anal glands contain mostly volatile organic compounds with a strong odor, and they are thus functionally involved in communication. Depending upon the species, they may be involved in territory marking, individual identification, and sexual signalling, as well as defense (such as in skunks). Their function in humans is unclear. Sebaceous glands within the lining secrete a liquid that is used for identification of members within a species. These sacs are found in many species of carnivorans, including wolves, bears, sea otters and kinkajous. Anatomy The human anal glands are situated within the wall of the anal canal and communicate with the lumen of the canal via ducts that open at the anal valves, just proximal to the pectinate line. Humans have 12 anal gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rodents
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are native to all major land masses except for Antarctica, and several oceanic islands, though they have subsequently been introduced to most of these land masses by human activity. Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial habitat, including human-made environments. Species can be arboreal, fossorial (burrowing), saltatorial/ricochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only a single upper and lower pair of ever-growing incisors. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, and hamsters. Once included with rodents, rabbits, hares, and p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Castoreum
Castoreum is a yellowish exudate from the castor sacs of mature beavers used in combination with urine to territorial marking, scent mark their territory. Both beaver sexes have a pair of castor sacs and a pair of anal glands, located in two cavities under the skin between the pelvis and the base of the tail. The castor sacs are not true glands (endocrine or exocrine) on a cellular level, hence references to these structures as preputial glands, castor glands, or scent glands are misnomers. It is extracted with alcohol from the dried and crushed castor sacs for use as a tincture in some perfumesInternational Perfume Museum, Grasse, France, Website: and, rarely, as a food additive. Chemical composition At least 24 compounds are known constituents of beaver castoreum. Several of these have pheromone, pheromonal activity, of which the phenols 4-ethylphenol and catechol and the ketones acetophenone and 3-hydroxyacetophenone are strongest. Five additional compounds elicit a wea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keystone Species
A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf and lion, are also apex predators. The role that a keystone species plays in its ecosystem is analogous to the role of a keystone in an arch. While the keystone is under the least pressure of any of the stones in an arch, the arch still collapses without it. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fur Trade
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of a world fur market in the early modern period, furs of boreal ecosystem, boreal, polar and cold temperate mammalian animals have been the most valued. Historically the trade stimulated the exploration and colonization of Siberia, northern North America, and the South Shetland Islands, South Shetland and South Sandwich Islands. Today the importance of the fur trade has diminished; it is based on pelts produced at fur farms and regulated fur-bearer trapping, but has become controversial. Animal rights organizations oppose the fur trade, citing that animals are brutally killed and sometimes skinned alive. Fur has been replaced in some clothing by synthetic fiber, synthetic imitations, for example, as in ruffs on hoods of parkas. Continental fur trade Russian fur trade Before the European colonization of the Americas, Russia was a major supplier of fur pelts to W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Urethra
The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated muscle that allows voluntary control over urination. The Internal urethral sphincter, internal sphincter, formed by the involuntary smooth muscles lining the bladder neck and urethra, receives its nerve supply by the Sympathetic nervous system, sympathetic division of the autonomic nervous system. The internal sphincter is present both in males and females. Structure The urethra is a fibrous and muscular tube which connects the urinary bladder to the external urethral meatus. Its length differs between the sexes, because it passes through the penis in males. Male In the human male, the urethra is on average long and opens at the end of the external urethral meatus. The urethra is divided into four parts in men, named after the lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Territory (animal)
In ethology, territory is the sociographical area that an animal consistently defends against conspecificity, conspecific competition (biology), competition (or, occasionally, against animals of other species) using agonistic behaviors or (less commonly) real physical aggression. Animals that actively defend territories in this way are referred to as being territorial or displaying territorialism. Territoriality is only shown by a minority of species. More commonly, an individual or a group of animals occupies an area that it habitually uses but does not necessarily defend; this is called its home range. The home ranges of different groups of animals often overlap, and in these overlap areas the groups tend to avoid each other rather than seeking to confront and expel each other. Within the home range there may be a ''core area'' that no other individual group uses, but, again, this is as a result of avoidance. Function The ultimate function of animals inhabiting and defendin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquatic Plants
Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquatic animals such as fish, amphibians and aquatic insects, create substrate for benthic invertebrates, produce oxygen via photosynthesis, and serve as food for some herbivorous wildlife. Familiar examples of aquatic plants include waterlily, lotus, duckweeds, mosquito fern, floating heart, water milfoils, mare's tail, water lettuce, water hyacinth, and algae. Aquatic plants require special adaptations for prolonged inundation in water, and for floating at the water surface. The most common adaptation is the presence of lightweight internal packing cells, aerenchyma, but floating leaves and finely dissected leaves are also common.Sculthorpe, C. D. 1967. The Biology of Aquatic Vascular Plants. Reprinted 1985 Edward Arnold, by London.Hu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
