The jaguar, Panthera onca, is the New World equivilent of the leopard. At first glance jaguars and leopards look very similar, but a more detailed comparison reveals several differences. The jaguar has a large head and is very stockily built with short legs, which make it look almost clumsy compared to the graceful leopard. The jaguar's 'spots' are also different, being larger, broken edged rosettes.
Albino jaguars have occasionally been reported (Seymour 1989) and melanism is frequent (Deutsch 1975, Dittrich 1979).
The fact that melanism is extremely frequent in the jaguar is explained by the fact that, unlike in the leopard, melanism is dominant over normal colouring in the leopard. This dominant melanism is also found in jungle cats and may be similar to the dominant 'sombre' mutation in mice, while the recessive melanism seen in leopards would be similar to the recessive 'non-agouti' mutation.
The following information is from von Dittrich's article 'Die vererbung des melanismus bein jaguar (Panthera onca'
I'm afraid my German isn't up to translating it, but luckily there is a summary in English:
Inheritance of Melanism in the Jaguar (Panther onca)
Melanism is frequently observed among the Felidae (Table 1). According to the crossing results of paired normal coloured and black jaguars (Panthera onca) and black jaguars between each other bred in several zoos (Table 2), melanism proves to be inherited as monogenic dominant to the normal coloured form, contrary to the rezessive (sic) inheritance of melanism in the leopard (Panthera pardus). A normal coloured cub besides black offspring of a pair of black Jungles cats (Felis chaus), bred in Cincinnati Zoo means dominant inheritance, like in the Jaguar, and black besides normal coloured cubs from a pair of normal coloured Pampas cats (Felis colocolo), bred in the same zoo, rezessive (sic) inheritance of melanism like in the leopard.
Table 1 lists the following species where melanism has been reported with references (Many in German)
Asiatic Golden cat
African Golden cat
and finally the Puma with reports from 1892, 1989 and 1946.
Table two lists the crosses
A Black jaguar male x black jaguar female:
9 litter, 17 young, 12 black and 5 normal
B Black jaguar male x normal female
24 liters; 47 young, 26 black, 21 normal
C normal jaguar male x black female
9 litters, 17 young, 5 black, 12 normal.
It is interesting to note that melanism in the Jungle cat is also dominant, as the possible contribution of Jungle cat genes the wildcats has already been discussed.
The paper also appears to mention a viable dominant melanistic mutation, "sombre", from the mouse, which I was unaware of, so dominant melanistic mutations may be more widespread than we suspected.
Deutsch, L.A. (1975) Contribuiçao paro o conhecimento da Panthera onca (Linne) - onça pintada (Mammalia Carnivora). Cruzamento de exemplares pintadas con melanicos. (In Portugese: Contributions to the knowledge of the jaguar: cross-breeding of spotted and melanistic forms.) Ciencias Biol. Secao 5, Zoologica 5: 369 - 370.
von Dittrich,L. (1979) Die vererbung des melanismus bein jaguar (Panthera onca). (In German: Heredity of melanism in jaguars (Panthera onca)) Zool. Garten. 49: 9 - 23.
Nowell, K. and Jackson, P. (Eds) (1993) Wild Cats. Status Survey and Conservation Action Plan. IUCN, Gland, Switzerland.
Seymour, K.L., (1989) Panthera onca. Mammalian Species. 340: 1 - 9.
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