|Panthera tigris × Panthera leo
The liger is a hybrid cross between a male Panthera leo (lion), and a female Panthera tigris (tiger) and is denoted scientifically as Panthera tigris × Panthera leo (Milne 1927). A liger resembles a giant lion with diffused stripes. While the Siberian tiger is the largest pure sub-species, ligers are the largest cats in the world. A similar hybrid, the offspring of a male tiger and a female lion is called a tigon.
While there is a great deal of diversity in nature, the rarity of ligers reflects that this diversity normally does not extend to mating between species. Rather, there tends to be a clear-cut boundary between species, reflecting a fundamental order in nature. Although lions and tigers are similar animals, belonging to the same genus, pairings between them are rare. Furthermore, male ligers (and male tigons) are sterile, so ligers themselves cannot mate and have offspring.
Ligers share physical and behavioral qualities of both parent species, forming spots and stripes on a sandy background. It is held that because the lion sire passes on a growth-promoting gene, but the corresponding growth-inhibiting gene from the female lion is absent, ligers grow far larger than either parent. Males have about a 50 percent chance of having a mane, but if they grow one, the mane will be modest, around 50 percent again of a pure lion mane.
In Animal Life and the World of Nature, A. H. Bryden (1906) 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 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 little or no trace of mane. It is a huge and very powerful beast.
Ligers have a tiger-like striping pattern on a lion-like tawny background. In addition, they may inherit rosettes (rose-like markings or formations, which are found in clusters and patches on the fur) from the lion parent, as 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 stripe-less ligers.
A black liger would require both a melanistic tiger and a melanistic lion as parents. (Melanism refers to increased amount of black or nearly black pigmentation.) 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.
The blue or Maltese tiger is now unlikely to exist, making grey or blue ligers an impossibility.
Imprinted genes may be a factor contributing to liger size. These are genes that may or may not be expressed depending on the parent they are inherited from, and that occasionally play a role in issues of hybrid growth. For example, in some mice species crosses, genes that are expressed only when maternally-inherited cause the young to grow larger than is typical for either parent species. This growth is not seen in the paternal species, as such genes are normally "counteracted" by genes inherited from the female of the appropriate species (HHMI 2000).
Another proposed hypothesis is that the growth dysplasia results from the interaction between lion genes and tiger womb environment. 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. This is not upheld by behavioral evidence—despite being sterile, many male ligers become sexually mature and mate with females. 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 pounds (320 kilograms) and reaching 10 feet (3.05 meters) long on average, but are often fertile.
Male ligers are sterile, but female ligers are often fertile.
According to Wild Cats of the World (1975) by C. A. W. Guggisberg, both male and female ligers and tigons were long thought to be sterile. In 1943, however, a 15-year-old hybrid between a lion and an 'Island' tigress was successfully mated with a lion at the Munich Hellabrunn Zoo. The female cub, even though very delicate, was raised to adulthood (Guggisberg 1975).
Because only female ligers and female tigons are fertile, a liger cannot reproduce with a tigon (offspring of male tiger and a lioness). This fertility is exhibited 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). Thus, the male liger and male tigon are sterile.
The fertility of hybrid big cat females is well-documented across a number of different hybrids and follows Haldane's rule.
If a liger were to reproduce with a tiger, it would be called a ti-liger, and if it were to reproduce with a lion, it would be called a li-liger.
Rare reports have been made of tigresses mating with lions in the wild (Courtney 1980). Under exceptional circumstances, it has been known for a tiger, Panthera tigris, to be forced into ranges inhabited by the Asiatic lion, Panthera leo persica. According to Ronald Tilson, the director of conservation at the Minnesota Zoo, this crossbreeding may have occurred in the Gir Forest in India where the ranges of Asiatic lions and Bengal tigers overlap. This combination of species in the wild, however, is considered highly unlikely.
According to the Association of Zoos and Aquariums (AZA), 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 (Mott 2005). However, they have admitted that ligers have occurred by accident. Several AZA zoos are reported to have ligers.
To follow are some of the reports of ligers:
This article incorporates text from messybeast.com, which is released under the GFDL.
All links retrieved August 6, 2014.
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