The Outstanding Beaver Engineer – Castor
Castor fiber, also known as the beaver, is a member of the rodent family Castoridae. Beavers are semi-aquatic mammals with a distinctive body shape, characterized by a large, rounded body, a large, flat tail, and powerful hind limbs. Their fur is thick and water-resistant, and they possess large, orange incisors that they use for gnawing wood.
Beavers are primarily nocturnal animals, spending most of the day in their lodges. They are excellent swimmers and divers, capable of holding their breath for several minutes. Unlike many other animals, they do not hibernate, instead maintaining a constant body temperature. Beavers have a poor self-defense ability and are timid, readily retreating into the water when startled.
The beaver has been listed as endangered by the International Union for Conservation of Nature (IUCN) in its 2008 Red List.
The beaver's large, rounded body is a key adaptation to its semi-aquatic lifestyle. Its head is short and blunt, with small eyes and a short neck. The forelimbs are short and have small feet with strong claws, while the hind limbs are powerfully built. The tail is large and flat, covered in horny scales and sparse fur. They have short ears with waterproof membranes.
Beaver skulls are adapted for gnawing wood, with exceptionally robust bone ridges and prominent sagittal and zygomatic crests. Their incisors are large and chisel-shaped, ideal for breaking off branches and trunks. Tooth formula: 20.
Beavers are primarily nocturnal, spending the day in their lodges. They are excellent swimmers and divers, capable of holding their breath for several minutes. Unlike many other animals, they do not hibernate, instead maintaining a constant body temperature. Beavers have a poor self-defense ability and are timid, readily retreating into the water when startled.
Beavers are primarily nocturnal, spending the day in their lodges. They are excellent swimmers and divers, capable of holding their breath for several minutes. Unlike many other animals, they do not hibernate, instead maintaining a constant body temperature. Beavers have a poor self-defense ability and are timid, readily retreating into the water when startled.
Beavers typically build their nests near water, with nest chambers constructed from twigs and mud, 0.8-1.9m above the ground. Beaver habitats can be broadly classified into three categories: denning, nesting, and combined den-nesting. Denning refers to permanent or temporary shelters. During the spring thaws, some beaver dams are flooded, forcing these beavers to relocate to temporary shelters on creeks or islands. Permanent dens are used for breeding and hibernation, and are structurally more complex. Den systems are generally found in higher riverbanks (above the ice line at 1.5m), while combined den-nesting systems are more common on mid-level riverbanks (1.5m below the ice line). Simple nests are built in marshes or shallow-water islands. These dens and nests are typically located in slow-flowing, deep water (generally 2m+ deep, 15m wide) in river bends. The entrances to the dens are usually 2-4 in number, often with submerged willow branches, and the tunnels are approximately 50cm high, 56cm wide, and can be up to 10m long. The enlarged chambers are typically 90cm high and 85cm wide.
Beavers primarily feed on a variety of vegetation, including tender branches, bark, and roots. They also consume aquatic plants such as willow, birch, and reeds. In summer, beavers forage for herbs such as,, water celery and grasses. In autumn, beavers often break off branches up to 1 meter long and carry them to the deep water near their dens to store as food for the winter.
Beaver predators include wolves, bears, and foxes. Cows also frequently knock down beaver dams during the winter, resulting in the beavers' death due to a lack of shelter.
Beavers typically breed once a year, with mating occurring in January-February, followed by birth in April-May, with litters of 1-6 pups. The gestation period is approximately 106 days, and the lactation period is about 2 months. Young beavers reach sexual maturity by their third year.
Beaver populations are not scattered. After 1900, the global beaver population decreased to approximately 1200 individuals; due to the implementation of conservation measures, in 1998, the global population was estimated to be 430,000, reaching 593,000 by 2002, and the lowest estimate in 2006 was 639,000. However, the number of beavers in Asia is very small. In 2002, the number of beavers in Mongolia was approximately 150, and in China, it was about 700. This population is showing an upward trend.
In China, due to ecological destruction and human factors, its distribution area has rapidly shrunk, and it is on the brink of extinction. As of 2012, the number of beavers in the Burlein River system in Xinjiang's Altay region fluctuates between 500-800, with 35 families in the Burlein River, 2 in the Chang River, and about 130 families in the Burlein River to the Urengu River confluence. In Mongolia, beaver protection is good, and the number is abundant. The Burlein River has approximately 40km of river on either side of the border, and some other rivers in Mongolia have been artificially transplanted with beavers. In China, the first and only beaver natural reserve in China was established in 1981 in the Burlein River valley in Xinjiang's Altay region.
The Burlein River Beaver Reserve is located in Xinjiang's Altay region, in the Burlein River valley on the Urengu River's 50km stretch, and protects the beaver habitat along the Burlein River, including the world's rare beaver species. The Burlein River flows eastward from Mongolia into China for 50km, and the area within 1km of the riverbanks on either side is included in the beaver reserve.
