Mutants are natural variations resulting from spontaneous genetic changes or the expression of recessive (hidden) genes due to inbreeding. Albinism (pure white), melanism (black) and unusual marking patterns are the commonest mutations. Such mutations occur in domestic cats so why are they less common in big cats? Wild cats displaying these traits may be less likely to survive to pass on the traits. In captivity, humans control which traits are bred, hence the multitude of domestic cat colours and types. In the wild, nature selects against any trait which does not enhance the animal's survival chances.
In the past, the obvious reaction to any unusual big cat was to shoot it for the trophy room. As a result, many interesting mutations may have been wiped out before the genes were passed on. Some colour mutations which would disadvantage a wild big cat are bred in captivity and are not viable in the wild. It is questionable whether these mutants should be perpetuated for the sake of curiosity or aesthetics alone.
The black jaguar is a relatively well known mutation. Black jaguars have been reported from Esmeralda, Venezuala and the junction of the Casiquiare and Orinoco rivers, also from south-eastern Brazil and from Paraguay (where Rengger (1830) reported black and chestnut skins). Jaguars also produce a variety of other colour and pattern oddities. The upper picture is Hemmer's pseudo-melanistic jaguar in which the markings have coalesced (merged) to give a blotched appearance. This is called abundism because markings are more abundant than normal. Some pseudo-melanistic jaguars have been reported as being black with tan or buff underparts, chest and throat (like a black-and-tan dog). On rare occasions, the black spots coalesce to produce a jet plack individual.
Below is a normal jaguar. The black jaguars spots still show up as the spot colour is denser than the background colour. Interestingly, melanism in jaguars is the result of a dominant gene (the gene is incompletely dominant and cats with 2 copies of the gene are darker than those with only one copy). In most other cat species it is a recessive (normally hidden) mutation. Black jaguars do not seem in any way disadvantaged by their mutation.
Black jaguar Kon (named for the Incan god of rain and wind) at Philadelphia Zoo
According to the “Illustrated Natural History” by the Rev JG Wood (1853, 1874): Sometimes, a black variety of the Jaguar is found, its colour being precisely similar to that of the Black Leopard, mentioned on page 169. The whole fur seems to take the tint of the dark spots, while the spots themselves are just marked by a still deeper hue. Probably, the cause of this curious difference in tint may he, that in the blood of the individual Jaguar there exists a larger quantity than usual of iron, which metal, as is well known, is found to form one of the constituents of blood. It can be extracted in the metallic form, and resembles very fine sand. In the human blood, late researches have discovered that the blood of the negro is peculiarly rich in iron, and it seems but reasonable that a similar cause will account for the very great variation in the leopard’s and Jaguar’s fur.
In Harmsworth Natural History (1910), WH Hudson " The jaguar is a beautiful creature, the ground-colour of the fur a rich golden-red tan, abundantly marked with black rings, enclosing one or two small spots within. This is the typical colouring, and it varies little in the temperate regions; in the hot region the Indians recognise three strongly marked varieties, which they regard as distinct species - the one described; the smaller jaguar, less aquatic in his habits and marked with spots, not rings; and, thirdly, the black variety. They scout the notion that their terrible ‘black tiger” is a mere melanic “ variation, like the black leopard of the Old World and the wild black rabbit. They regard it as wholly distinct, and affirm that it is larger and much more dangerous than the spotted jaguar ; that they recognise it by its cry; that it belongs to the terra firma rather than to the water-side; finally, that black pairs with black, and that the cubs are invariably black. Nevertheless, naturalists have been obliged to make it specifically one with Felis onca, the familiar spotted jaguar, since, when stripped of its hide, it is found to be anatomically as much like that beast as the black is like the spotted leopard. "
"Ghost jaguars" are sometimes reported. They have greyish white fur with faint markings on the flanks and have been reported in Paraguay. Albino jaguars with almost invisible markings have also been reported. Albino and partially albino jaguars have been reported from Paraguay. Spanish soldier-naturalist Don Felix de Azara described a jaguar so pale that its rosettes were only visible in certain lights. Rengger described a greyish white skin with faint shades of markings on the belly and flanks, the claws had been white according to the hunter who shot the animal.
In March 2012, a pair of white jaguar cubs were born at the Aschersleben Zoo in the state of Saxony-Anhalt, Germany. The parents were a 17-year-old spotted male named Mescal and 13-year-old black female named Molly (Molly was jet black rather than black-on-charcoal, indicating she was homozygous for melanism). The cubs have pale grey markings on a white background. Because there are two white cubs, and because ghost jaguars have occurred in the wild, it is likely the parents both carry a recessive gene for the colour. It is also possible that one or other parent has a novel dominant mutation in the germ cells (the eggs or sperm) - this would show up in the offspring, but not in the parents. It would be necessary to mate the cubs back to the parents, and to unrelated jaguars, to determine whether the mutation is dominant or recessive. There is a risk that this novel colour will become pupular in the same way that white tigers are popular, resulting in inbreeding to fix and perpetuate the trait.
There is also the possibility of red (erythristic) jaguars resulting from the non-extension gene although I am not aware of any reports (the red mutation has been seen on several occasions in leopards). Leopard-spotted jaguars are reported sporadically from Peruvian rainforest.
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For more information on the genetics of colour and pattern:
Robinson's Genetics for Cat Breeders & Veterinarians 4th Ed (the current version)
Genetics for Cat Breeders, 3rd Ed by Roy Robinson (earlier version showing some of the historical misunderstandings)
Cat Genetics by A C Jude (1950s cat genetics text; demonstrates the early confusion that chinchilla was a form of albinism)
For more information on genetics, inheritance and gene pools see:
The Pros and Cons of Inbreeding
The Pros and Cons of Cloning
For more information on anomalous colour and pattern forms in big cats see
Karl Shuker's "Mystery Cats of the World" (Robert Hale: London, 1989 - some of the genetics content is outdated)
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