The history of ligers dates Essay

The history of ligers dates to at least the early 19th century in India. In 1798, Étienne Geoffroy Saint-Hilaire (1772–1844) made a colour plate of the offspring of a lion and a tiger. In 1825, G. B. Whittaker made an engraving of liger cubs born in 1824.[3] The parents and their three liger offspring are also depicted with their trainer in a 19th-century painting in the naà ¯ve style. Two liger cubs born in 1837 were exhibited to King William IV and to his successor Queen 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 â€Å"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.[4] 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 340 kg (750 lb) and stood a foot and a half (45 cm) 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 â€Å"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.† Size and growth The liger is often believed to represent the largest known cat in the world.[1] Males reach a total length of 3 to 3.5 m,[6][7] meaning they are the size of large Siberian tiger males.[8] Imprinted genes may be a factor contributing to huge liger size.[9] 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 â€Å"counteracted† by genes inherited from the female of the appropriate breed.[10] Other big cat hybrids can reach similar sizes; the litigon, a rare hybrid of a male lion and a female tiglon, is roughly the same size as the liger, with a male named Cubanacan (at the Alipore Zoo in India) reaching 363 kg (800 lb).[11] The extreme rarity of these second-generation hybrids may make it difficult to ascertain whether they are larger or smaller, on average, than the liger. It is wrongly believed that ligers continue to grow throughout their lives due to hormonal issues.[citation needed] It may be that they simply grow far more during their growing years and take longer to reach their full adult size. Further growth in shoulder height and body length is not seen in ligers over 6 years old, same as both lions and tigers. Male ligers also have the same levels of testosterone on average as an adult male lion, yet areazoospermic in accordance with Haldane’s rule. In addition, female ligers may also attain great size, weighing approximately 320 kg (705 lb) and reaching 3.05 m (10 ft) long on average, and are often fertile. In contrast,pumapards (hybrids between pumas and leopards) tend to exhibit dwarfism. Hercules and Sinbad[ Jungle Island, an interactive animal theme park in Miami, is home to a liger named Hercules, the largest non-obese liger, who is recognised by the Guinness Book of World Records as the largest living cat on Earth, weighing over 410 kg (904 lb).[12] Hercules was featured on the Today Show, Good Morning America, Anderson Cooper 360, Inside Edition and in a Maxim article in 2005, when he was only three years old and already weighed 408.25 kg (900 lb). Hercules is 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 reportedly similar in weight to Hercules. Longevity[Shasta, a ligress (female liger) was born at the Hogle Zoo in Salt Lake City on 14 May 1948 and died in 1972 at age 24.[citation needed] Valley of the Kings animal sanctuary in Wisconsin had a male liger named Nook who weighed around 550 kg (1,213 lb), and died in 2007, at 21 years old. Hobbs, a male liger at the Sierra Safari Zoo in Reno, Nevada, lived to almost 15 years of age before succumbing to liver failure and weighed in at 410 kilograms (900 lb). Fertility 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 sex is determined by sex chromosomes, if one sex 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, 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, though of delicate health, was raised to adulthood.[13] In September 2012, the Russian Novosibirsk Zoo announced the birth of a â€Å"liliger†, which is the offspring of a liger mother and a lion father. The cub was named Kiara. Appearance Colour plate of the offspring of a lion and tiger, Étienne Geoffroy Saint-Hilaire Ligers have a tiger-like striped pattern that is very faint upon a lionesque 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 colour may be correspondingly tawny, sandy or golden. In common with tigers, their underparts are pale. The actual pattern and colour depends on which subspecies the parents were and on how the genes interact in the offspring. White tigers have been crossed with lions to produce â€Å"white† (actually pale golden) ligers. In theory, white tigers could be crossed with white lions to produce white, very pale or even stripeless ligers. There are no black ligers. 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. As blue or Maltese Tigers probably no longer exist, grey or blue ligers are exceedingly improbable. It is not impossible for a liger to be white, but it is very rare Ligers in the wild: It is unlikely a mating of this type would ever occur in the wild, for a number of reasons. Firstly, lion and tiger habitats do not meet, though you’ll often hear claims that they overlap in one area of the world, this being the Gir National Park and Lion Sanctuary in Bangladesh. The truth is tigers are not found within 100 miles of Gir Forest. Within the sanctuary itself is the only lion subspecies found outside of Africa. This is the very rare Asiatic lion (only a few hundred remain and they face extinction). The lion rules in Gir Forest and no tigers are found there. Tigers are not found in Africa, and are restricted to Asia. Though it is conceivable that a tiger may cross into lion territory, both species are so rare that it is highly unlikely the two would ever meet. On top of this, the Gir Forest is surrounded by farming and agriculture. The lions within the sanctuary are effectively captive in the wild and tigers do not like to cross large stretches of open ground. What would happen if the two species did meet? The very solitary tiger would be little inclined to join in with the more social pride of lions. Apart from periods of mating, tigers even go out of their way to avoid their own species. The Tigon is a hybrid cross between a male Tiger and a female Lion WHY ARE LIGERS SO MUCH BIGGER THAN TIGONS? The large size of the liger and small size of the tigon is due to â€Å"genomic imprinting† – the unequal expression of genes depending on parent of origin i.e. whether certain growth genes are inherited from the male or the female. This is linked to the species’ lifestyle and breeding strategy – whether the female mates with only one male while in heat (non-competitive) or whether she mates with many males (competitive). This results in â€Å"growth dysplasia†. The following explanation is greatly simplified as a number of other genes are contributed unequally by the male and female parents and also affect the general health and longevity of the offspring. Lions live in prides led by several adult males. The lionesses mate with each of those males. Each male wants his offspring to be the ones to survive, but the female’s genes want multiple offspring to survive. The father’s genes promote size of the offspring to ensure that his offspring out-compete any other offspring in the womb at the same time. Genes from the female inhibit growth to ensure that as many offspring as possible survive and that they all have an equal chance. By contrast, tigers are largely solitary and a female on heat normally only mates with one male. There is no competition for space in the womb so the male tiger’s genes do not need to promote larger offspring. There is therefore no need for the female to compensate, so the offspring’s growth goes uninhibited. When a male lion mates with a tigress, his genes promote large offspring because lions are adapted to a competitive breeding strategy. The tigress does not inhibit the growth because she is adapted to a non-competitive strategy. Therefore the offspring (liger) grows larger and stronger than either parent because the effects do not cancel each other out. Ligers take several years to reach full adult size, but it is a myth that ligers never stop growing. When a male tiger mates with a lioness, his genes are not promoting large growth of the offspring because he is adapted to a non-competitive breeding strategy. However, the lioness is adapted to a competitive strategy and her genes inhibit the growth of the offspring. This uneven match means that the offspring (tigons) are often smaller and less robust than either parent. Growth dysplasia has other effects: the size of the placenta may be affected (causing miscarriage), the embryo may be aborted at an early stage due to abnormal growth, the cub may be stillborn or may only survive a few days. In some rodents, mating Species A males with Species B females produces offspring half normal size, but mating Species B males with Species A females cause the offspring to be aborted as they try to grow to several times the normal size. Because of the impossibility of a gene being inherited from only females, there is a competing hypothesis. This hypothesis (allthough not tested) is that the Lion’s sperm is damaged somehow during fertilization and that a growth inhibiting gene is typically destroyed. It is impossible for a gene carried on a chromosomes to be passed along only from the mother. The reason for this is there are no chromosomes that only a female can have. Female Tigons and Female Ligers both possess a tiger X chromosme and a lion X chromosome, yet only the female Ligers will grow large, this means something must happen to either alter the genes or that the cause of the growth dysplasia lies at least partially outside of the genes. Another possible hypothesis is that the growth dysplasia results from the interaction between lion genes and tiger womb enviroment. The tiger produces a hormone that sets the fetal Liger on a pattern of growth that does not end throughout his life. The hormonal hypothesis is that the cause of the male Liger’s growth is his sterility – essentially, the male liger remains in the pre-pubertal growth phase. This is not upheld by behavioural evidence – despite being sterile, many male ligers become sexually mature and mate with females. In addition, female ligers also attain great size but are fertile.