Liger
From Wikipedia, the free encyclopedia
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The liger, is a hybrid cross between a male lion and a female tiger (i.e, Panthera leo × Panthera tigris[1]). A liger resembles a tiger with diffused stripes. They are the largest cats in the world, although the Siberian Tiger is the largest "pure" taxon. Ligers and tigers enjoy swimming, whereas lions do not. A similar hybrid, the offspring of a male tiger and a female lion is called a tigon.
Rare reports have been made of tigresses mating with lions in the wild.[2] Such mating may have occurred when, in uncommon circumstances, tigers were forced into ranges inhabited by the Asiatic Lion, Panthera leo persica. However, since the present-day ranges of wild lions and tigers no longer overlap,[3] it is generally held that such a combination of species would occur very rarely.[4]
History
Documentation of ligers dates to at least the early 19th century in Asia. A painting of two liger cubs was made by Étienne Geoffroy Saint-Hilaire (1772−1844). In 1825, G.B. Whittaker made an engraving of liger cubs born in 1824. The parents and their three liger offspring are also depicted with their trainer in a 19th Century painting in the naïve style.
Two liger cubs born in 1837, were exhibited to William IV and to his successor Victoria. On 14 December 1900 and on 31 May 1901, Carl Hagenbeck wrote to zoologist James Cossar Ewart with details and photographs of ligers born at the Hagenbeck's Tierpark in Hamburg in 1897.
In Animal Life and the World of Nature (1902–1903), A.H. Bryden described Hagenbeck's "lion-tiger" hybrids:
It has remained for one of the most enterprising collectors and naturalists of our time, Mr Carl Hagenbeck, not only to breed, but to bring successfully to a healthy maturity, specimens of this rare alliance between those two great and formidable felidae, the lion and tiger. The illustrations will indicate sufficiently how fortunate Mr Hagenbeck has been in his efforts to produce these hybrids. The oldest and biggest of the animals shown is a hybrid born on the 11th May, 1897. This fine beast, now more than five years old, equals and even excels in his proportions a well-grown lion, measuring as he does from nose tip to tail 10 ft 2 inches in length, and standing only three inches less than 4 ft at the shoulder. A good big lion will weigh about 400 lb [...] the hybrid in question, weighing as it does no less than 467 lb, is certainly the superior of the most well-grown lions, whether wild-bred or born in a menagerie. This animal shows faint striping and mottling, and, in its characteristics, exhibits strong traces of both its parents. It has a somewhat lion-like head, and the tail is more like that of a lion than of a tiger. On the other hand, it has no trace of mane. It is a huge and very powerful beast.[5]
In 1935, four ligers from two litters were reared in the Zoological Gardens of Bloemfontein, South Africa. Three of them, a male and two females, were still living in 1953. The male weighed 750 lb. and stood a foot and a half taller than a full grown male lion at the shoulder.
Although ligers are more commonly found than tigons today, in At Home In The Zoo (1961), Gerald Iles wrote "For the record I must say that I have never seen a liger, a hybrid obtained by crossing a lion with a tigress. They seem to be even rarer than tigons."[6]
[edit] Size and growth
Imprinted genes may be a factor contributing to liger size.[7] These are genes that may or may not be expressed on the parent they are inherited from, and that occasionally play a role in issues of hybrid growth. For example, in some dog breed crosses, genes that are expressed only when maternally-inherited cause the young to grow larger than is typical for either parent breed. This growth is not seen in the paternal breeds, as such genes are normally "counteracted" by genes inherited from the female of the appropriate breed.[8]
The tiger produces a hormone that sets the fetal liger on a pattern of growth that does not end throughout its life. The hormonal hypothesis is that the cause of the male liger's growth is its sterility — essentially, the male liger remains in the pre-pubertal growth phase. Male ligers also have the same levels of testosterone on average as an adult male lion. In addition, female ligers also attain great size, weighing approximately 700 lb (320 kg) and reaching 10 feet (3.05 m) long on average, and are often fertile.
[edit] Hercules and Sinbad
Jungle Island in Miami is home to a liger named Hercules, the largest non-obese liger, said to weigh over 1,100 lbs, over twice the size of a male lion. Hercules was also featured on the Today Show, Good Morning America, Anderson Cooper 360, Inside Edition and in a Maxim magazine article in 2005, when he was only 3 years old and already weighed 408.25 kg (900 lb) at the time.[citation needed] The liger is the largest animal in the cat family (feline family Felidae);[9][10] and Hercules was in the Book of World Records as the largest cat. Hercules seems completely healthy and is expected to live a long life. The cat's breeding is said to have been a complete accident. Sinbad, another Liger, was shown on the National Geographic Channel. Sinbad was reported to have the exact weight of Hercules.
[edit] Longevity
Shasta, a ligress (female liger) was born at the Hogle Zoo in Salt Lake City on May 14, 1948 and died in 1972 at age 24. The 1973 Guinness world records reported an 18-year-old, 798-kg (1,756 lb) male liger living at Bloemfontein zoological gardens, South Africa, in 1888. Valley of the Kings animal sanctuary in Wisconsin had a male liger named Nook who weighed around 550 kg (1,210 lb), and passed away in 2007, at 21 years old.
[edit] Fertility
While male ligers are sterile, female ligers can usually reproduce. Because only female ligers and tigons are fertile, a liger cannot reproduce with another liger or with a tigon. The offspring from a coupling of a female liger and a male tiger is referred to as a ti-liger, while the offspring produced from a female liger and a male lion is referred to as a li-liger.
The fertility of hybrid big cat females is well-documented across a number of different hybrids. This is in accordance with Haldane's rule: in hybrids of animals whose gender is determined by sex chromosomes, if one gender is absent, rare or sterile, it is the heterogametic sex (the one with two different sex chromosomes e.g. X and Y).
According to Wild Cats of the World (1975) by C. A. W. Guggisberg, ligers and tigons were long thought to be sterile: In 1943, however, a fifteen-year-old hybrid between a lion and an 'Island' tiger was successfully mated with a lion at the Munich Hellabrunn Zoo. The female cub, although of delicate health, was raised to adulthood.[11]
[edit] Colors
Ligers have a tiger-like striping pattern on a lion-like tawny background. In addition they may inherit rosettes from the lion parent (lion cubs are rosetted and some adults retain faint markings). These markings may be black, dark brown or sandy. The background color may be correspondingly tawny, sandy or golden. In common with tigers, their underparts are pale. The actual pattern and color depends on which subspecies the parents were and on the way in which the genes interact in the offspring.
White tigers have been crossed with lions to produce "white" (actually pale golden) ligers. In theory white tigers could be crossed with white lions to produce white, very pale or even stripeless ligers. A black liger would require both a melanistic tiger and a melanistic lion as parents. Very few melanistic tigers have ever been recorded, most being due to excessive markings (pseudo-melanism or abundism) rather than true melanism. No reports of black lions have ever been substantiated. A hypothetical procedure to breed black ligers is explained here. The blue or Maltese Tiger is now unlikely to exist, making gray or blue ligers an impossibility. It is not impossible for a liger to be white, but it is very rare.
[edit] Zoo policies
According to the Association of Zoos and Aquariums, accredited zoos frown on the practice of mixing two different species and have never bred ligers. Keeping the two species separate has always been standard procedure.[12] However they have admitted that ligers have occurred by accident. Several AZA zoos are reported to have ligers.
Wolf Dogs
Wolf-dog hybrid
From Wikipedia, the free encyclopedia
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 wolf-dog hybrid that has malamute ancestry | ||||
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A wolf-dog hybrid (also called a wolf hybrid or wolfdog) is a canid hybrid resulting from the mating of a wolf (Canis lupus) and a dog (Canis lupus familiaris). The term "wolfdog" is preferred by most wolfdog proponents and breeders since the domestic dog was recently taxonomically recategorized as a subspecies of wolf. Professional organizations such as the American Veterinary Medical Association and government agencies such as the United States Department of Agriculture refer to the animals as wolf-dog hybrids.[1] Rescue organizations consider any animal with wolf heritage within the last five generations to be a wolfdog, including some established wolfdog breeds.[2]
In 1998, the USDA estimated an approximate population of 300,000 wolfdogs in the United States (the highest of any country world-wide), with some other sources giving a population possibly as high as 500,000.[1] In first generation hybrids, gray wolves are most often crossed with wolf-like dogs (such as German Shepherd Dogs, Siberian Huskies, and Alaskan Malamutes) for an appearance most appealing to owners desiring to own an exotic pet.[3] Since wolf hybrids are genetic mixtures of wolves and dogs, their physical and behaviorial characteristics cannot be predicted with any certainty.[1]
History
[edit] Origins
Evidence for prehistoric domesticated wolfdogs in the Americas dates back at least 10,000 years[4] while fossil evidence in Europe points to their use in hunting mammoths.[5] Noted historic cases (such as the Cevennes, France wolf-attack incidents of 1764-1767) of large wolves that were abnormally aggressive toward humans, may be attributable to wolf-dog mating.[1] In terms of intentional breeding efforts, the first documented wolfdog breed, the Saarlooswolfhond, did not begin to be developed until the 1920's. Hybrids were used as experimental attack dogs in South Africa under apartheid.[6]
[edit] Breed-specific legislation
The wolfdog hybrid has been the center of much controversy for much of its history, and most breed-specific legislation is either the result of the animal's perceived danger or a categorization as protected native wildlife.[7] The Humane Society of the United States, the RSPCA, local Canadian Humane Societies, the National Canine Defense League and the Wolf Specialist Group of the IUCN Species Survival Commission consider wolfdogs to be wild animals and therefore unsuitable as pets, and support an international ban on the private possession, breeding and sales of wolf-dog hybrids.[8] [9] [10] According to the National Wolfdog Alliance, 40 U.S. states effectively forbid the ownership, breeding and importation of wolfdogs, while others impose some form of regulation upon ownership.[11] Most European nations, as well as many U.S. states and municipalities, also either outlaw the animal entirely or put restrictions on ownership.[12][13].
[edit] Wolf-dog hybrids and threatened wolf populations
Hybridization in the wild usually occurs near human habitations where wolf density is low and dogs are common.[14] However, there were several reported cases of wolf-dogs in areas with normal wolf densities in the former Soviet Union. [15] In Europe, unintentional matings of dogs and wild wolves has been confirmed in some populations through genetic testing. As the survival of some Continental European wolf packs is severely threatened, scientists fear that the creation of wolf-dog hybrid populations in the wild is a threat to the continued existence of European wolf populations.[16] However, extensive wolf-dog hybridization is not supported by morphological evidence, and analyses of mtDNA sequences have revealed that such matings are rare.[14] However, since mtDNA is mainly maternally inherited and most cases of hybridization in the wild seem to occur between a female wolf and a male domestic dog, these results may not be reliable.
[edit] Description
The physical characteristics of an animal created by breeding a wolf to a dog are not predictable, similar to that of mixed-breed dogs. Genetic research shows that wolf and dog populations initially diverged approximately 10,000 years ago and have interbred only occasionally since; thus imbuing the dissimilarity between dogs and wolves in behavior and appearance.[17] In many cases the resulting adult wolfdog may be larger than either of its parents due to the genetic phenomenon of heterosis (known to laypersons as hybrid vigor).[1] Hybrids display a wide variety of appearances, ranging from a resemblance to dogs without wolf blood to animals that are often mistaken for full-blooded wolves. A lengthy study by DEFRA and the RSPCA found several examples of misrepresentation by breeders and indeterminate levels of actual wolf pedigree in many animals sold as wolfdogs. The report noted that uneducated citizens misidentify dogs with wolf-like appearance as wolfdogs.[18] In some cases, the presence of dewclaws is considered a useful, but not absolute indicator of dog gene contamination in wild wolves. Dewclaws are the vestigial fifth toes of the hind legs common in domestic dogs but thought absent from pure wolves, which only have four hind toes.[16] Observations on wild wolf hybrids in the former Soviet Union indicate that wolf hybrids in a wild state may form larger packs than pure wolves, and have greater endurance when chasing prey.[19] High content hybrids typically have longer canine teeth than dogs of comparable size, with some officers in the South African Defence Force commenting that the animals are capable of biting through the toughest padding "like a knife through butter".[6]
[edit] Health
Wolf-dog hybrids are generally said to be naturally healthy animals, and are affected by less inherited diseases than most breeds of dog. Wolfdogs are usually healthier than either parent due to heterosis.[1] Some of the established breeds of wolfdog that exist today were bred specifically to improve the health and vigor of working dogs.
There is some controversy over the effectiveness of the standard dog/cat rabies vaccine on a wolfdog. The USDA has not to date approved any rabies vaccine for use in wolf-dog hybrids, though they do recommend an extra-label use of the vaccine.[20] Wolfdog owners and breeders purport that the lack of official approval is a political move to prevent condoning wolfdog ownership.[21]
[edit] Temperament and behavior
Wolf-dog hybrids are a mixture of genetic traits, which results in less predictable behavior patterns compared to either the wolf or dog.[1] This is not to say that the behavior of any specific hybrid is erratic. It would, however, be unlikely that someone unfamiliar with an individual animal would be able to predict that animal's behavior with reasonable certainty. The adult behavior of hybrid pups also cannot be predicted with comparable certainty to dog pups, even in third-generation pups produced by wolfdog matings with dogs or from the behavior of the parent animals.[1] Thus, though the behavior of an individual wolf hybrid may be predictable, the behavior of the type as a whole is not.[1]
According to the CDC and the Humane Society of the United States, the wolfdog ranks sixth in the number of dog attack fatalities in the U.S.; with 14 hybrid-related fatalities between 1979 and 1998 in the United States.[22] [23] In 2000, DEFRA and the Royal Society for the Prevention of Cruelty to Animals released a lengthy study that attributed much of the reported aggressiveness of wolfdogs to the characteristics of the breeds of dogs the wolves are bred with. With both wolves' and dog's social habits revolving around a pack structure, wolfdogs may not show the dog's natural acceptance of humans as the dominant pack members, possibly resulting in physical confrontations.[1] Some purport that attacks may not even be caused by typical behavior patterns of aggression and dominance present in either parent species, but instead may be related to predatory instincts, as the majority of attacks involve small children.[1] Between 1981 and 1999, there have been 38 severe attacks and 13 fatalities caused by wolf hybrids in North America, with all victims being children.[24] An officer in the South African Defence Force once commented that it was very difficult to dissuade wolf hybrids from pressing an assault once an attack was initiated.[6]
Most wolf and wolfdog rescue organizations maintain wolfdogs retain many of the traits and requirements of their wild relatives and therefore may be inappropriate as domestic pets.[25][26] The view that aggressive characteristics are inherently a part of wolfdog temperament has been contested in recent years by wolfdog breeders and other advocates of wolfdogs as pets.[27][28] Proponents of wolfdogs as pets say that the animals are naturally timid and fearful of humans, but that with proper training and responsible ownership wolfdogs can become good pets.[29] [30] Even in cases of wolfdogs displaying consistently dog-like behavior, they often retain the wolf's natural curiosity; driving them to dig ferociously, chew up household items such as furniture and display extreme difficulty in housebreaking.[1] [31]
[edit] Breeds
Today, four breeds of dog exist that utilized a significant amount of recent wolf-dog hybridization in their creation. All of the breeds were the result of intentional crosses with German Shepherd Dogs, and have distinguishing characteristics of appearance that may reflect the varying subspecies of wolf that contributed to their foundation stock. The intention in creating the breeds was manifold; ranging from the desire for a recognizable companion wolfdog, to military working dogs. The eldest breed, the Saarlooswolfhond, traces its origins to the efforts of a Dutch breeder in 1921. This first attempt at sustained wolf-dog crossing was to improve Shepherd breeding stock and prevent canine distemper. Though this effort failed, today the FCI and the Dutch Kennel Club both recognize the breed. In the 1950's, the Kunming Wolf-dog was created, as a working military dog. In the 1950's the Czechoslovakian Wolfdog was also created to work on border patrol in the countries now known as Slovakia and the Czech Republic. It is recognized by the Foundation Stock Service of the American Kennel Club AKC, the United Kennel Club UKC, and the FCI, and today is used in agility, obedience, search and rescue, police work, therapy work, and herding in Europe and the United States.
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