Question: How long have Bison been kept at Golden Gate Park?
About the article "Golden Gate Park", section "Bison paddock".

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Bison ("Bison bison") have been kept in Golden Gate Park since 1891, when a small herd was purchased by the park commission.
At the time, the animal's population in North America had dwindled to an all-time low, and San Francisco made a successful effort to breed them in captivity.
In 1899, the paddock in the western section of the park was created.
At its peak and through a successful captive breeding program, more than 100 calves were produced at Golden Gate Park, helping preserve the iconic bison population numbers in North America, which has been critical to the culture and livelihood of Native Americans.
In 1984, Mayor Dianne Feinstein's husband, Richard C. Blum, purchased a new herd as a birthday present for his wife.
The older bison in the paddock today are descendants of those animals.
In December 2011, after the number of bison in the paddock had dwindled to three, Assemblywoman Fiona Ma’s office led another preservation effort.
With donations from the Theodore Rosen Charitable Foundation, Richard C. Blum, and the Garen Wimer Ranch, Assemblywoman Ma’s office worked with the San Francisco Zoo and SF Recreation and Parks to add seven new bison to the existing herd.
The Paddock is currently open to the public for viewing.
The Wind Cave bison herd is considered to be genetically pure, meaning that there is no evidence of significant hybridization between these bison and cattle.
Most private and public bison herds in the United States are not genetically pure.
Genetic testing shows that there now appear to be some cattle genes present in approximately 95% of the bison surveyed in other areas.
Though the American bison (Species: "Bison bison") is not only a separate species, but a member of a separate genus from domestic cattle ("Bos primigenius"), they are genetically compatibile and American bison can interbreed freely with cattle.
Crossbreeds tend to look very much like purebred bison, so appearance is unreliable as a means of determining what is a purebred bison and what is a crossbred cow.
Many ranchers deliberately crossbred their bison with cattle, 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 have been common.
Most bison today are descendants of five herds that were conserved during the near-extinction event of the late 19th century.
These herds were subject to cattle crossbreeding experiments and as a result cattle genes are found throughout most bison populations.
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 crossbred 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, perhaps only 15,000 to 25,000 of these bison are pure and are not actually bison-cattle hybrids.
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 in Canada and herds derived from it.
A landmark study of bison genetics was undertaken by James Derr of Texas A&M University in an attempt to determine what genetic problems bison might face as they repopulate former areas.
It concluded that bison seem to be doing quite well, despite their apparent genetic bottleneck.
All of the state-owned bison herds tested contained animals with domestic cattle mitochondrial DNA, with the possible exception of the Henry Mountains bison herd of Utah.
Most national herds, except Wind Cave and Yellowstone, also appear to be hybridized.
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.
This is significant for the Wind Cave bison herd, since this herd was founded, in part, with animals from the Yellowstone Park bison herd.
The bison in Wind Cave National park were also plains bison, as expected. 
Antelope Island in Great Salt Lake, Utah, is part of Antelope Island State Park.
On the island, a semi–free-ranging population of American bison ("Bison bison, "buffalo) has been in existence since 1893.
Though the island was named for the pronghorn antelope that John C. Frémont and Kit Carson found there when they explored the Great Salt Lake, bison were later introduced and the island is now perhaps most famous for its bison herd.
The Antelope Island bison herd is significant because it is one of the largest and oldest publicly owned bison herds in the nation.
It is one of the two bison herds managed by the State of Utah, the other being the Henry Mountains bison herd.
The Antelope Island bison herd currently numbers between 550 and 700 individuals.
Other large free-ranging, publicly controlled herds of bison in the United States include the Yellowstone Park bison herd (3,500 bison), the herd in Custer State Park, South Dakota (1,300 bison), the Henry Mountains bison herd in south-central Utah (300 to 500 animals), the herd at Wind Cave National Park in South Dakota (350 bison), and the 400-strong National Bison Range Herd near Flathead Lake, Montana.
In addition, though the bison on Antelope Island are Prairie bison, which was the most common bison subspecies in North America, the bison have a distinct genetic heritage from many of the other bison herds in the United States and they are considered to be desirable as part of the breeding and foundation stock for other bison herds, because of their separate genetic heritage and some of the distinct genetic markers that are found in the population.
Buffalo watching is one of the most popular activities on Antelope Island.
In fact, the island is perhaps best known for the bison that inhabit it, and the bison are generally easily found and observed. 
The Henry Mountain bison herd is considered to be genetically pure, meaning that there is no evidence of significant hybridization between these bison and cattle.
This genetic purity appears to be different from the Antelope Island bison herd, also managed by the State of Utah.
In the Antelope Island bison herd, there now appear to be some cattle genes present.
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 ("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 started 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 seem to be doing quite 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 isn't 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.
It was originally founded with bison from the Yellowstone Park Bison Herd.
However, the extension of this herd into the Book Cliffs of Central Utah involved mixing the founders with additional bison from another source, so it is not known if the Book Cliff extension of the herd is also free of cattle hybridization.
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 scientists had previously suggested that the Yellowstone bison were either of the "athabascae" (Wood bison) subspecies, or that they were a type of 'Mountain bison' subspecies.
It was determined by the study 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.
Since the Yellowstone Park herd are Plains bison, that would indicate that the Henry Mountain herd are also Plains bison. 
Two of the major problems that bison face today are the genetic bottleneck and lack of genetic diversity that has been caused by the very small number of bison that survived their near extinction event.
A second genetic problem is the entry of genes from domestic cattle into the bison population, through hybridization.
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 ("Bison bison") is not only a separate species, but is usually regarded as being in a separate genus from domestic cattle ("Bos primigenius"), they clearly have a lot of genetic compatibility and American bison can interbreed with cattle, although only the female offspring are fertile in the first generation.
These female hybrids can be bred back to either bison or domestic bulls, resulting in either 1/4 or 3/4 bison young.
Female offspring from this cross are also fertile, but males are not reliably fertile unless they are either bison or domestic.
Moreover, when they do interbreed, crossbreed animals in the first generation 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 known to contain 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 started 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 seem to be doing quite 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 national, state and private 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.
It is also notable that the Henry Mountain herd was started initially with transplanted animals from Yellowstone Park.
However, the extension of this herd into the Book Cliffs of central Utah involved mixing the founders with additional bison from another source, so it is not known if the Book Cliffs extension of the herd is also free of cattle hybridization.
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.
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".
However, the Yellowstone Park bison herd were pure plains bison, and not any of the other previously suggested subspecies.
Another interesting finding was that the bison in the Antelope Island bison herd in Utah appeared to be more distantly related to other plains bison in general than any other plains bison group that was tested, though this might be due to genetic drift caused by the small size of only 12 individuals in the founder population.
A side finding of this was that the Antelope Island bison herd appears to be most closely related to the Wood Buffalo National Park bison herd, though the Antelope Island bison are actually plains bison.