Yellowstone Park bison herd
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The Yellowstone Park bison herd in Yellowstone National Park is probably the oldest and largest public bison herd in the United States. Yellowstone is known for its geothermal activity and large mammals, especially elk, wolves, American bison, bears, pronghorns, moose and bighorn sheep. The Yellowstone Park bison herd is estimated at approximately 3,700 individuals (2011) in two major sub-herds. The bison in the Yellowstone Park bison herd are American bison, and of the Plains bison subspecies. Yellowstone National Park may be the only location in the United States where free ranging bison were never extirpated, since they continued to exist in the wild and were not re-introduced as has been done in most other bison herd areas. Other large free ranging, publicly controlled herds of Bison in the United States include the Wind Cave bison herd (approximately 350 animals), the Antelope Island bison herd (approximately 550 to 700 animals), the Henry Mountains bison herd in Utah (400 to 500 animals), and the National Bison Range herd near Flathead Lake, Montana (400 animals).
The Yellowstone Park bison herd is actually divided into two sub-herds that are mostly isolated from each other. The Northern Range herd which numbers approximately 2300 individuals ranges from the northern entrance near Gardiner, Montana through the Blacktail Plateau and into the Lamar Valley. The Central Interior herd which numbers approximately 1400 individuals ranges from the Madison River valley into the Hayden Valley and Upper and Lower Geyser Basins.
"Bison" in Yellowstone Park are perhaps more frequently called "Buffalo" by park visitors. The term "buffalo" is sometimes considered to be a misnomer for this animal, as it is only distantly related to either of the two "true buffalo", the Asian water buffalo and the African buffalo. However, "bison" is a Greek word meaning ox-like animal, while "buffalo" originated with the French fur trappers who called these massive beasts bœufs, meaning ox or bullock—so both names, "bison" and "buffalo", have a similar meaning. Though the name "Bison" might be considered to be more scientifically correct, as a result of standard usage the name "buffalo" is also considered correct and is listed in many dictionaries as an acceptable name for American Buffalo or bison. In reference to this animal, the term "buffalo", dates to 1635 in North American usage when the term was first recorded for the American mammal. It thus has a much longer history than the term "bison", which was first recorded in 1774. The American bison is very closely related to the wisent or European bison.
American Bison once numbered in the millions, perhaps between 25 million and 60 million by some estimates, and they were possibly the most numerous large land animal on earth. However by the late 1880s, they had been hunted to near extinction throughout North America. It appears that the Yellowstone Park Bison Herd was the last free ranging bison herd in the United States and the only place where bison were not extirpated in the United States. The Yellowstone Park Bison Herd is descended from a remnant population of 23 individual bison that survived the mass slaughter of the 19th century by hiding out in the Pelican Valley of Yellowstone Park. In 1902, a captive herd of 21 Goodnight plains bison was introduced to the park and then moved to the Lamar Valley and managed as livestock until the 1960s, when a policy of natural regulation was adopted by the park.
American Bison live in river valleys, and on prairies and plains. Typical habitat is open or semi-open grasslands, as well as sagebrush, semi-arid lands and scrublands. Some lightly wooded areas are also known historically to have supported bison. Bison will also graze in hilly or mountainous areas where the slopes are not steep. Though not particularly known as high altitude animals, bison in the Yellowstone Park Bison Herd are frequently found at elevations above 8,000 feet and a herd started with founder animals from Yellowstone, the Henry Mountains bison herd, is found on the plains around the Henry Mountains, Utah, as well as in mountain valleys of the Henry Mountains to an altitude of 10,000 feet.
Bison are large herd animals that defend their young vigorously. American bison can run up to 35 miles per hour and are surprising agile, in addition to their notable strength and irritable temperament. Significant apex predators that are found in Yellowstone National Park including American black bears, Grizzly bears and wolves. Other large mammals found in Yellowstone include elk, moose, coyotes, bobcats, deer, pronghorn, and bighorn sheep. Wolves and bears are clearly successful predators of bison, but bison does not comprise the major portion of their diet. Competitive pressure from the other large grazing mammals in Yellowstone Park may also help limit the number of bison in the herd, but this is not considered to have a significant effect on bison numbers. Disease, including various viruses, parasites and brucellosis have a greater effect on bison population. However, a common cause of death for these bison continues to be hunting by human beings. This occurs when many of the bison leave the park during the winter, heading up into Montana, especially through the Lamar Valley. At such times, the State of Montana has authorized large buffalo hunts, to eliminate the animals, because of concerns about spreading brucellosis to local domestic cattle.
The Yellowstone Park bison herd is considered to be genetically pure, meaning that there is no evidence of significant hybridization between these bison and cattle.
Officially, the "American Buffalo" is classified by the United States Government as a type of cattle, and the government allows private herds to be managed as such. This is a reflection of the characteristics that bison share with cattle. Though the American bison (Species: Bison bison) is not only a separate species, but actually in a separate genus from domestic cattle (Bos primigenius), they clearly have a lot of genetic compatibility and American Bison can interbreed freely with cattle. Moreover, when they do interbreed, the crossbreeds tend to look very much like purebred bison, so appearance is completely unreliable as a means of determining what is a purebred bison and what is a crossbred cow. Many ranchers have deliberately cross bred their cattle with bison, and it would also be expected that there could be some natural hybridization in areas where cattle and bison occur in the same range. Since cattle and bison eat similar food and tolerate similar conditions, they have often been in the same range together in the past, and opportunity for cross breeding may sometimes have been common.
In recent decades tests were developed to determine the source of mitochondrial DNA in cattle and bison, and it was found that most private 'buffalo' herds were actually cross bred with cattle, and even most state and federal buffalo herds had some cattle DNA. With the advent of nuclear microsatellite DNA testing, the number of herds that contained cattle genes has increased. Though approximately 500,000 bison exist on private ranches and in public herds, some people estimate that perhaps only 15,000 to 25,000 of these bison are pure and are not actually bison-cattle hybrids. "DNA from domestic cattle (Bos taurus) has been detected in nearly all bison herds examined to date." Significant public bison herds that do not appear to have hybridized domestic cattle genes are the Yellowstone Park bison herd, the Henry Mountains bison herd which was started with bison taken from Yellowstone Park, the Wind Cave bison herd and the Wood Buffalo National Park bison herd and subsidiary herds descended from it, in Canada.
A landmark study of bison genetics that was performed by James Derr of the Texas A&M University corroborated this. The Derr study was undertaken in an attempt to determine what genetic problems bison might face as they repopulate former areas, and it noted that bison were faring well, despite their apparent genetic bottleneck. One possible explanation for this might be the small amount of domestic cattle genes that are now in most bison populations, though this is not the only possible explanation for bison success.
In the study cattle genes were also found in small amounts throughout most herds. "The hybridization experiments conducted by some of the owners of the five foundation herds of the late 1800s, have left a legacy of a small amount of cattle genetics in many of our existing bison herds." He also said, "All of the state owned bison herds tested (except for possibly one) contain animals with domestic cattle mtDNA." It appears that the one state herd that had no cattle genes was the Henry Mountains bison herd in the Henry Mountains of Utah, which were descended from transplanted animals from Yellowstone Park. It is unknown if the Book Cliffs extension of this herd in Central Utah is also free of hybridization; the extension involved mixing the founders with additional bison from another source.
There is currently no evidence of hybridization in the Yellowston herd, however, some geneticists speculate that as genetic testing improves, it may be discovered that almost all bison have some genetic inheritance from domestic cattle.
A separate study by Wilson and Strobeck, published in Genome, was done to define the relationships between different herds of bison in the United States and Canada, and to determine whether the bison at Wood Buffalo National Park in Canada and the Yellowstone Park bison herd were possibly separate subspecies, and not Plains bison. Some people had suggested that the Yellowstone Park bison were actually either of the 'athabascae' (wood buffalo) subspecies, or else that they were of an unspecified 'mountain' subspecies. In the study, it was determined that the wood buffalo park bison were actually cross breeds between plains bison and wood bison, but that their predominant genetic makeup was truly that of the expected "wood buffalo" (Bison bison athabascae). However, the Yellowstone Park bison herd were pure plains bison (Bison bison bison), and not any of the other previously suggested subspecies.
There remain various questions and concerns regarding future management of the Yellowstone Park Bison Herd. Current US National Park Service policy is to let the herd take a natural course, as much as possible, and no definitive attempt is made to control or eliminate disease, most notably brucellosis. This is analogous to the policy of the park service to let natural wildfires burn themselves out, except in areas where they cause a threat to structures or habitation. However, there are many people who advocate a vigorous attempt to eliminate brucellosis from the herd. This would require rounding all the animals up for vaccination and culling, or a new form of vaccination would need to be developed that could be applied without capturing all the animals. In addition, even if brucellosis were eliminated from the herd, there is a question whether the bison herd might become re-infected from other potential natural sources, such as elk.
Hunting is not allowed inside Yellowstone National Park but bison, wolves, elk and other animals that leave the park are not necessarily protected. There continues to be public controversy over the hunting of the animals in Montana when the bison leave the park. Some groups have proposed that all hunting must stop, but that is currently under the control of the State of Montana.
The bison at Yellowstone National Park have become the foundation animals for many other bison herds throughout the United States, such as the Henry Mountains bison herd and (partially) the Wind Cave bison herd, and many groups in the United States and Canada are making efforts to return Bison to much of their previous natural range. If there are large tracts of open range and natural habitat that become available for bison, then some private groups have actually purchased these lands and some lands are in the process of being prepared for bison introduction. Currently, some state and national parks have habitat for bison, but most of these already have bison present. In moving bison to new locations, great care should be taken to maintain their genetic diversity, to ensure that valuable genes are not irrevocably lost. Care should also be taken when dealing with any already existing herd, to try to minimize the introduction of domestic cattle genes, which appear to be carried by many bison, into herds where such genes are not currently present.
|Images of Yellowstone bison|
|Wikimedia Commons has media related to Bison in Yellowstone.|
- "Yellowstone bison population estimated to be smaller than last year's". Bozeman Chronicle. Retrieved 2011-08-29.
- The American Heritage Dictionary of the English Language, Fourth Edition
- National Park Service 
- Texas Parks and Wildlife Magazine