Two million years ago, a terrifying predator commonly known as the "American short-faced bear" lived in the northern part of the North American continent. Because their main prey is buffalo and bison, they are sometimes called "cattle bears." At that time, North American short-faced bears mainly included two species: Arctodus simus and Arctodus pristinus. The so-called giant short-faced bear refers to Arctodus simus. They were the largest carnivores in the vast area from Alaska to Yukon at that time.
Characteristics of the giant short-faced bear:
In addition to the large mouth full of sharp teeth, the most striking feature of the giant short-faced bear is its long limbs. When they usually walk When it was standing, its back was about 1.5 meters from the ground, and when it stood up on its hind limbs, it was more than 3.4 meters (the largest short-faced bear fossil found in North America so far stands up to 4.3 meters).
However, although the giant short-faced bear is much taller than the American ancient brown bear (Ursus arctos) of the same period, its weight is not as heavy as people think, because although their limbs are very long, they are Relatively "slender", paleontologists estimate that even in autumn, the weight of giant short-faced bears is only about 700 kilograms. Now Canada's largest polar bear weighs 660 kilograms, and the famous cave bear among bears ( Ursus spelaeus) exceeds a ton.
In terms of physical characteristics, the forehead of the giant short-faced bear is different from other bears. They have the same broad forehead as today’s African lions; the short-faced bear’s face is indeed short enough, and its width and length The ratio is 80% (while brown bears, black bears and Pleistocene cave bears are all less than 70%). With such short and wide jaws and well-developed muscle tissue, it is no wonder that the giant short-faced bear became the most powerful in North America at that time. apex predator.
Another "distinctive" thing about short-faced bears is that almost all late bears walk with their toes turned inward, so they always look "shambling" . This is not the case with short-faced bears. They have evolved a straight walking pace, which allows them to move easily and run quickly.
The origin of short-faced bears in America:
Like other bears, the short-faced bears of both subfamilies in North America originated from the dawn of Europe in the early Miocene. Bear (Ursavus), by the middle of the Pliocene Epoch, a branch of the Ursavus descendants came to North America. In order to better chase prey, they developed longer limbs and became the so-called running bears. There are two main evolutionary paths for running bears: one is the spectacled bears (Tremarctos) that still exist in the dense forests of South America. Their body structure is relatively close to their primitive ancestors and they eat plants as their staple food; radially developed, (although until today, we have not found the direct ancestor of the American short-faced bear), one of them evolved into the most dominant predator on the North American continent-the short-faced bear. (Short-faced bears even entered South America and successfully evolved into South American short-faced bears, including Arctodus bonariensis, a carnivorous beast with huge canine teeth, and Arctodus brasiliensis, a smaller, omnivorous animal.)
The development of short-faced bears in North America:
Among the two short-faced bears that have survived in the North American continent, the smaller Arctodus pristinus is not well-known, but its body The structure is relatively primitive, with a long and narrow skull and smaller teeth, so Arctodus pristinus short-faced bears are likely to be omnivorous. Since the early Pleistocene, they have lived in the Pacific coastal forests from Alaska to Mexico. Among them, due to their similar food and living environment, they are competing species with American black bears. By the late Pleistocene, ancient brown bears invaded the Americas from Asia in large numbers, which undoubtedly accelerated the decline of this species of short-faced bears.
Unlike Arctodus pristinus, which lived in the forest, the giant short-faced bear (Arctodus simus) roamed the vast North American savanna at that time, and they were found as far north as the Yukon Territory to Alaska. The body structure of the giant short-faced bear and its well-developed canine teeth indicate that it has strong explosive power and speed, which ensures that the giant short-faced bear can reach its prey (American bison, Oriole, caribou, three-toed horses, ground otters, etc.) The success rate when hunting, and successfully defeated other carnivorous beasts (including American Smilodon saber-toothed tigers, North American lions, ancient brown bears, dire wolves, mountain lions and other powerful opponents), becoming the largest and most terrifying predator on the North American continent in the Pleistocene.
Through fossil records, scientists have also discovered that giant short-faced bears usually lead a "lonely" life, with males and females only getting together during mating periods. During the period when the mother is nursing her young, she often has no time to hunt and becomes a scavenger in the grasslands or bushes.
The giant short-faced bears became extinct with the arrival of the last ice age in North America. There are different opinions on the reasons. The previous explanation was that the large herbivores in North America were extinct one after another at that time, resulting in a shortage of food for the short-faced bears.
But now it is discovered that this hypothesis has many doubts. Through systematic research on ancient brown bear fossils in the Yukon, scientists have discovered that the ancient brown bears that migrated under the pressure of giant short-faced bears quickly returned to North America after the short-faced bears became extinct. The northern part of the continent has successfully filled the ecological space left by the short-faced bears and has thrived to this day. This reminds us that the extinction of short-faced bears in North America has a deeper reason that we currently do not know.
Short-faced bears take large herbivores as their main food. Others should be expected to eat fish or plant food, but it will definitely be a fraction. The impact of Quaternary glaciers on our country is not great, but it has The influence of North America and Europe was very huge, especially in North America. During this period, a large number of large herbivores certainly disappeared, but not all of them were extinct. However, at the same time, the huge ground sloths, alpacas, ancient pronghorns, and North American deciduous animals Elephants are extinct, bison and other species must also be greatly reduced. Short-faced bears are directly restrained and their numbers are reduced. If we consider food, this statement is more reasonable. After the short-faced bears are greatly reduced, vacuum zones and some areas must have appeared. The mating and genetic exchange of short-faced bears were cut off, and "isolated islands" appeared. At this time, other bears invaded the North American continent for the second time and quickly occupied the vacuum zone. Moreover, these bears were still omnivorous and had more advantages in terms of food and adaptation. After all, the number of short-faced bears was reduced now. At this time, the short-faced bear not only faced challenges from nature, but also faced fierce competition. It also faced the embarrassing environment of being unable to mate or finding a mate. The combination of these three forces contributed to the faster decline of the short-faced bear. The invasion of humans into North America is another reason that restricts short-faced bears. Although we cannot say how big it is, it certainly plays a certain role.
American bison, red deer and other large herbivores were greatly reduced during the ice age. Later, due to the lack of predator threats, they quickly recovered, until the number of tens of millions in the 16th century? The number is abnormal. The reduction of vegetarian animals directly affects carnivores, especially during the Ice Age. The decrease in carnivorous animals has, to a certain extent, reduced the pressure on vegetarian animals to survive. Now the bison's main enemy is the wolf, not the bear! But in prehistory, bears were mortal enemies. Bears definitely prey on adult bison to control the number of bison, while modern wolves basically prey on larvae and immature individuals to suppress the number of bison. The only large grassland vegetarian animals in North America now include deer, pronghorn, and native bison. Wild horses and the like are all secondary introductions. There are few species but naturally large numbers. If there were as many species as in Africa, then a more complicated and prosperous situation would probably occur.