Their large size and highly carnivorous dentition supports the proposal that the dire wolf was a predator that fed on large prey. Dire wolves were absent north of 42°N latitude in the Late Pleistocene; therefore, this region would have been available for Beringian wolves to expand south along the glacier line. These cycles would have caused increased temperature and aridity, and at La Brea would have caused ecological stress and therefore food stress. G. K. Warren, U. S. Top. Because the rules of nomenclature stipulated that the name of a species should be the oldest name ever applied to it, Merriam therefore selected the name of Leidy's 1858 specimen, C. :149 Over 200,000 specimens (mostly fragments) have been recovered from the tar pits, with the remains ranging from Smilodon to squirrels, invertebrates, and plants. The most commonly broken teeth are the canines, followed by the premolars, carnassial molars, and incisors.  In 1918, after studying these fossils, Merriam proposed consolidating their names under the separate genus Aenocyon (from Aenos, terrible and cyon, wolf) to become Aenocyon dirus, but not everyone agreed with this extinct wolf being placed in a new genus separate from the genus Canis. These plant communities suggest a winter rainfall similar to that of modern coastal southern California, but the presence of coast redwood now found 600 kilometres (370 mi) to the north indicates a cooler, moister, and less seasonal climate than today. The fossil evidence from the Americas points to the extinction mainly of large animals, termed Pleistocene megafauna, near the end of the last glaciation. dirus. It can be assumed that dire wolves lived in packs of relatives that were led by an alpha pair.  In 1908 the paleontologist John Campbell Merriam began retrieving numerous fossilized bone fragments of a large wolf from the Rancho La Brea tar pits.  A study of nine modern carnivores found that one in four adults had suffered tooth breakage and that half of these breakages were of the canine teeth. Wolf-like species of Canis apparently originated there, and then returned to North America. The dire wolf (Canis dirus, "fearsome dog") is an extinct species of the genus Canis. Fossil specimens of C. dirus discovered at four sites in the Hay Springs area of Sheridan County, Nebraska, were named Aenocyon dirus nebrascensis (Frick 1930, undescribed), but Frick did not publish a description of them. For over 20 years, Yukon-Charley Rivers National Preserve has monitored up to twelve wolf packs that routinely utilize Preserve lands. , The results of a study of dental microwear on tooth enamel for specimens of the carnivore species from La Brea pits, including dire wolves, suggest that these carnivores were not food-stressed just before their extinction. , C. d. guildayi is estimated to have weighed on average 60 kg (130 lb), and C. d. dirus weighed on average 68 kg (150 lb) with some specimens being larger, but these could not have exceeded 110 kg (240 lb) due to skeletal limits. These characteristics are thought to be adaptations for preying on Late Pleistocene megaherbivores, and in North America its prey are known to have included horses, ground sloths, mastodons, bison, and camels. The Yukon government implemented the Yukon Wolf Conservation and Management Plan in 1983 in response to a decline in caribou numbers in the Ross River region. The dire wolf probably evolved from Armbruster's wolf (Canis armbrusteri) in North America. Like the gray wolf today, the dire wolf probably used its post-carnassial molars to gain access to marrow, but the dire wolf's larger size enabled it to crack larger bones. Two subspecies are recognized: Canis dirus guildayi and Canis dirus dirus. Canines are the teeth most likely to break because of their shape and function, which subjects them to bending stresses that are unpredictable in both direction and magnitude. The solitary hunter depends on a powerful bite at the canine teeth to subdue their prey, and thus exhibits a strong mandibular symphysis. As with other large Canis hypercarnivores today, the dire wolf is thought to have been a pack hunter.  The finds at San Josecito Cave and El Cedazo have the greatest number of individuals from a single locality. In Alaska in 2009, the Department of Fish and Game allowed the aerial hunting of wolves in order to reduce the population by 200. The Santa Monica Mountains supported a chaparral community on its slopes and isolated coast redwood and dogwood in its protected canyons, along with river communities that included willow, red cedar, and sycamore. This beast was reported to be 230 pounds and was killed in Canada, Drayton Valley. It is considered a subspecies, called Canis lupus pambasileus, and also goes by the names Alaskan black wolf, Interior Alaskan wolf and Alaskan wolf. Thus, researchers can use the strength of the mandibular symphysis in fossil carnivore specimens to determine what kind of hunter it was – a pack hunter or a solitary hunter – and even how it consumed its prey.  The majority of fossils from the eastern C. d. dirus have been dated 125,000–75,000 YBP, but the western C. d. guildayi fossils are not only smaller in size but more recent; thus it has been proposed that C. d. guildayi derived from C. d.  As their prey became extinct around 10,000 years ago, so did these Pleistocene carnivores, except for the coyote (which is an omnivore). Arctic GraylingArctic Ground SquirrelBear (Black)Bear (Grizzly)BeaverCanada GooseCanada LynxCaribou (Woodland)CoyoteDall SheepElkFox (Arctic)Golden EagleMooseMountain GoatMule DeerMuskoxenNorthern GoshawkNorthern PikeOspreyPeregrine FalconPine MartinPorcupinePtarmiganRavenSnowshoe HareSnowy OwlSwallowTrumpeter SwanWolfWolverineWood BisonYukon's Arctic Char. Eng., by Dr. F. V. Hayden, Geologist to the Expedition, Proceedings", "Notice of some fossil bones discovered by Mr. Francis A. Lincke, in the banks of the Ohio River, Indiana", "The extinct mammalian fauna of Dakota and Nebraska, including an account of some allied forms from other localities, together with a synopsis of the mammalian remains of North America", "Description of some remains of an extinct species of wolf and an extinct species of deer from the lead region of the upper Mississippi", "Human remains and associated fossils from the Pleistocene of Florida", "Note on the systematic position of the wolves of the Canis dirus group", "The Code online (refer Chapter 6, article 23.1)", "The fauna of Rancho La Brea, Part II. :148 The following year, a study yielded evidence that led to the conclusion that C. dirus and C. nehringi were the same species and thus that C. dirus had migrated from North America into South America, making it a late participant in the Great American Interchange. Feeding upon a wide variety of animal species such as deer or elk, Northwestern wolves control the numbers of their populations, thus benefiting different animal and plant species of their range. These also became extinct at the end of the Late Pleistocene, as did the dire wolf. R. Knight.  The Ice Age reached its peak during the Last Glacial Maximum, when ice sheets began advancing from 33,000 YBP and reached their maximum limits 26,500 YBP. The dire wolf broke its incisors more often when compared to the modern gray wolf; thus, it has been proposed that the dire wolf used its incisors more closely to the bone when feeding.  Both the dire wolf and the Beringian wolf went extinct in North America, leaving only the less carnivorous and more gracile form of the wolf to thrive, which may have outcompeted the dire wolf. areas of the Yukon, wolves are territorial strongly defending their area from other wolves. How widely they were then distributed is not known. The risk of tooth fracture is also higher when killing large prey. :243 The early wolf from China, Canis chihliensis, may have been the ancestor of both C. armbrusteri and the gray wolf C.