HYBRIDS BETWEEN TIGER SUBSPECIES
The classification and naming of tigers continues to change as classification based on range or appearance is overtaken by classification based on DNA. The nomenclature used on this site may reflect that used on specimens at the time they were documented rather than their current name.For convenience the following nomenclature is found in current and historical literature about tigers. Royal Bengal, Burmese and Indian all refer to the Bengal tiger (Panthera tigris tigris). The Manchurian, Siberian and North China tiger all refer to the Amur tiger (P t altaica). Amoy and Xiamen are alternate names for the South China tiger (P t amoyensis). The Indochinese is also known as Corbett's tiger (P t corbetti). The other living subspecies are the Malayan (P t jacksoni) and Sumatran (P t sumatran) tigers. Extinct subspecies are the Caspian (Persian) (P t virgata), Balinese (P t balica) and Javan (P t sondaica).
MANCHURIAN TIGER/BENGAL TIGER HYBRID
This is a hybrid between 2 subspecies of tiger. It is a museum specimen of a zoo-bred Manchurian (North China/Amur) x Bengal tiger hybrid showing traits intermediate between the pale fluffy Manchurian tiger and the smaller, darker Bengal. It has more prominent striping on the hindquarters and tail than on the forequarters. Now displayed in Natural History Museum, London.
Panthera tigris altaica (Amur/Siberian Tiger) x P tigris tigris (Bengal Tiger): Three hybrids were born in Birmingham, USA in 1965.
JM Dolan (1971) reported a single viable cub born to a pair of Siberian x Bengal hybrids. Other reports: DP Groves (1971), International Zoo Yearbook (1965, 1967, 1971)
Hybrids between Siberian/Amur and Bengal tigers are very common as the 2 subspecies have become extremely mongrelized in circus and menagerie populations, especially through breeding white tigers. Both the male and female hybrids between the subspecies are fertile among themselves and when bred to other tiger subspecies.
Until comparatively recently many of the tigers in zoos, safari parks and circuses were mongrels with a mix of Bengal and Siberian (Amur) blood. Recent emphasis on conserving gene pools has led to separate breeding of these species in reputable zoos and safari parks and the registration of tigers in studbooks. Because circuses have a different agenda – showy animals and entertainment rather than conservation – their tigers will more often be of mixed blood. Other collections – private collections, breeders for the exotic pet trade and non-conservation minded zoos – are also less concerned with bloodline purity.
The Messybeast webpage on white tigers details the mongrelisation between the 2 species in order to mass-produce white tigers as zoo attractions and circus acts. Some of the mongrel orange offspring from white tiger breeding programmes were bred with orange Bengal tigers, leading to the introduction of Siberian tiger genes into the captive Bengal tiger population. Some apparently pure Siberian tigers were probably hybrids that were registered as pure Siberian (e.g. a tiger described as an Amur and having descendents registered and bred as Amur tigers might have been described elsewhere as Amur/Bengal).
While a low level of alien genes is "genetic pollution" the damage may already have been done and may be so widespread as to be irreversible. It is not practical to replenish zoo stocks from the dwindling wild populations. After careful and repeated breeding back to known purebred stock, the percentage of alien genes is reduced to less than 1% and, for practical purposes, such animals may have to be regarded as "pure-bred".
BENGAL X SIBERIAN HYBRIDS IN DHUDHWA TIGER RESERVE, INDIA
In 1978, in an attempt to increase the genetic diversity of the tiger population in India, tigers from different populations were to be introduced into the Dhudhwa tiger reserve in India. A cub (Tara) from the UK's Twycross Zoo was to be released into the reserve. Prior to release into the wild, Tara was discovered to be a Bengal x Siberian hybrid. However, she escaped from her enclosure into the reserve where she probably bred. In the 1990s, some Dhudhwa tigers were observed which had the typical appearance of Siberian tigers: white complexion, pale fur, large head and wide stripes.
Mitochondrial analysis indicates that Indian (Bengal) and Siberian tiger species diverged around 80,000 to 100,000 years ago. Hair samples of some of the Dhudhwa tigers showed the mitochondria to be of the Bengal type. However, Tara may have had a Bengal mother and a Siberian father, in which case her mitochondria would be of the Bengal type, but her nuclear DNA would be a mix of Bengal and Siberian types. As her offspring bred together, they would inherit varying proportions of Bengal and Siberian genes with the result that some would be more Siberian in appearance.
OTHER TIGER SUBSPECIES HYBRIDS
A Siberian x Bengal hybrid mated with a Sumatran tiger (P t sumatrae) resulting in a triple hybrid in Zurich, Switzerland, 1963. A Siberian tiger mated with a Bengal x Sumatran hybrid in Kaunas, Lithuania (formerly USSR).
P t amoyensis (Amoy/Chinese Tiger) x P t tigris (Bengal Tiger): Three female hybrids were born at Rostov, Russia in 1967, one of which survived. International Zoo Yearbook (1969).
P t sumatrae (Sumatran Tiger) x P t tigris (Bengal Tiger): Four male hybrids and 3 female hybrids were born at Grodno, Belarus (formerly USSR) in 1969. Three of the females and one of the males died. A Sumatran x Bengal hybrid at Kaunas, Lithuania (formerly USSR) was mated to an Amur tiger resulting in 2 male and 1 female offspring. One of the males did not survive. International Zoo Yearbook (1971).
Hybrids between different tiger subspecies are relatively common and are regarded as mongrels because they don't contribute to conservation efforts. Some hybrids are bred accidentally.
Tiger Creek Wildlife Refuge in Tyler, Texas have some less common hybrid tigers. They have two Amur/Sumatran hybrids named China and Thai, turned over to the sanctuary by a private individual. They also have Indo-Chinese/Amur tigers named Gunther and Kiarra who were the result of an accidental breeding between Lexie (female) and Piffer (male), who had grown up together and shared a pen. Piffer was believed to be sexually immature at the time.
REFERENCES AND FURTHER READING
For more information on the genetics of colour and pattern:
Robinson's Genetics for Cat Breeders & Veterinarians 4th Ed (the current version)
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