Monday, July 11, 2011

dangerous wolves & dangerous wolves mammals

The gray wolf or grey wolf (Canis lupus), often known simply as the wolf, is the largest extant wild member of the Canidae family. Though once abundant over much of Eurasia, North Africa and North America, the gray wolf inhabits a reduced portion of its former range due to widespread destruction of its territory, human encroachment, and the resulting human-wolf encounters that sparked broad extirpation. Even so, the gray wolf is regarded as being of least concern for extinction by the International Union for Conservation of Nature, when the entire gray wolf population is considered as a whole. Today, wolves are protected in some areas, hunted for sport in others, or may be subject to population control or extermination as threats to livestock, people, and pets.
dangerous wolvesGray wolves are social predators that live in nuclear families consisting of a mated pair, their offspring and, occasionally, adopted immature wolves. They primarily feed on ungulates, which they hunt by wearing them down in short chases. Gray wolves are typically apex predators throughout their range, with only humans and tigers posing significant threats to them.

Genetic studies reaffirm that the gray wolf is the ancestor of the domestic dog. A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion.

In areas where human cultures and wolves both occur, wolves frequently feature in the folklore and mythology of those cultures, both positively and negatively.
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dangerous wolves imagesCanis lepophagus, a small, narrow skulled North American canid of the Miocene era, which may have also given rise to coyotes. Some larger, broader skulled C. lepophagus fossils found in northern Texas may represent the ancestral stock from which true wolves derive. The first true wolves began to appear at the end of the Blancan North American Stage and the onset of the early Irvingtonian. Among them was Canis priscolatrans, a small species closely resembling the red wolf, which colonised Eurasia by crossing the Bering land bridge. The new Eurasian C. priscolatrans population evolved into Canis etruscus, then Canis mosbachensis.

This primitive wolf closely resembled the modern southern wolf populations of the Arabian Peninsula and South Asia, which were once distributed in Europe in the early Quaternary glaciation until about 500,000 years ago (see Subspecies).[4] C. mosbachensis evolved in the direction of Canis lupus, and recolonised North America in the late Rancholabrean era. There, a larger canid species called Canis dirus was already established, but it became extinct 8,000 years ago after the large prey it relied on was wiped out. Competition with the newly arrived gray wolves for the smaller and swifter prey that survived may have contributed to its decline. With the extinction of dire wolves, gray wolves became the only large and widespread canid species left.

The North American recolonisation likely occurred in several waves, with the most distinctive populations occurring in the periphery of the range. These populations (C. l. arctos on the high arctic islands, C. l. lycaon in the eastern forests, C. l. baileyi in the far south and C. l. rufus at the continental corner opposite the point of invasion) may represent survivors of early migrations from Eurasia. C. l. baileyi, C. l. lycaon and C. l. rufus display some primitive traits and systematic affinity to one another. Fossil remains from the late Pleistocene of large bodied wolves similar to C. l. arctos and C. l. albus occur in coastal southern California, indicating that large North American gray wolf subspecies were once widespread, and may have been driven southward by glaciation, though wolves no longer reside there. Fossils of small bodied wolves similar to C. l. baileyi have been found in a range encompassing Kansas and southern California. This indicates a late Pleistocene population flux, in which large, Arctic forms of wolf moved farther south, with smaller, warmth adapted wolves expanding as the climate moderated.
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Studies on the genetic distance for mitochondrial DNA on dogs and Eurasian wolves confirmed that wolves are the exclusive ancestral species to dogs. Domestic dogs possess four mtDNA lineages, suggesting four independent domestication events. A later study identified mtDNA evidence suggesting a common origin from a single East Asian gene pool for all dog populations, while another, using a much larger data set of nuclear markers, points to the Middle East as the source of most of the genetic diversity in the domestic dog and a more likely origin of domestication events. A study by the Kunming Institute of Zoology found that the domestic dog is descended from wolves tamed less than 16,300 years ago south of the Yangtse river in China. Morphological comparisons have narrowed the likely ancestral subspecies of gray wolf to wolves of the Middle Eastern and South Asian variety.

The actual domestication process is a source of debate. Although it is popularly assumed that dogs are the result of artificial selection, the general intractability of adult wolves to human handling has led certain experts to theorise that the domestication process occurred through natural selection when Mesolithic human communities began building permanent settlements in which a new ecological niche (middens and landfills) was opened to wolves. These wolves would have formed a commensal relationship with humans, feeding on their waste over many generations, with natural selection favouring assertive wolves with shorter flight distances in human presence, and causing physical changes related to the redundancy of features adapted for hunting big game.

Although dogs are the most closely related canids to gray wolves (the sequence divergence between gray wolves and dogs is only 1.8%, as opposed to over 4% between gray wolves, Ethiopian wolves and coyotes),[22] there are a number of physical and behavioural differences. Comparative studies on dog and wolf behaviour and anatomy have shown that dog physiology and most dog behaviours are comparable to those of young wolves, an example of neoteny and pedomorphism.
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