In the 2004 coming-of-age cult-classic movie Napoleon Dynamite, Napoleon is seen drawing a mystical, striped cat creature in his notebook. When asked what it is, he says “a liger... it's pretty much my favourite animal. It's a cross between a lion and a tiger, bred for its skills and magic.”
And yes, ligers do exist – though it's highly questionable whether they are bred for skills and magic. Ligers are the result of a mating between a male lion and a female tiger.
A tigon is the opposite: a male tiger and a female lion. There are even leopons: a result of male leopards breeding with female lions. And finally, there's the jagualep: when a male jaguar breeds with a female leopard.
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So yes, big cats - species in the Genus Panthera that include lions, tigers, leopards and jaguars - can crossbreed with each other but this has only ever occurred in captivity.
A key reason that big cat species do not interbreed in the wild is that their ranges seldom overlap. For instance, lions and tigers have enormous distributions in Africa and Asia respectively, but they only meet in the Gir Forest in India's Gujarat region and here their different habits and behaviours mean they stay well clear of each other.
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The leopard's range overlaps more with those of lions and tigers but if the larger species encounter leopards, their instinct is invariably to drive them away aggressively.
Jaguars live in South America where they do not encounter other Panthera species.
In addition to these ecological barriers, the species just aren't interested in each other, say big cat experts, in the same way that humans aren't drawn to chimps.
So it is captivity where crossbreeding occurs and is even encouraged. Ligers are the most common of these hybrids and are generally much larger than either parent species weighing up to 400kg compared to a tiger's 300kg and 250kg for a male lion. Ligers can be sociable like lions but also display tiger behaviour such as swimming. Their vocalisations contain elements of both parents.
Such a massive, unusual animal provides a 'wow' factor for some zoos and can attract big and lucrative crowds. Many more big-cat hybrids are bred for private animal collections that are hidden from the public, primarily in the US, Russia and China – and the number may be growing.
Big cat scientists disapprove of such 'designer hybrid' cross-breeding, calling it unethical. “With hybrids there’s a much greater chance of the genetics being messed up,” said Luke Hunter head of Panthera an organisation that works to conserve big cats. In an article for National Geographic Magazine, Hunter explained that this can lead to a higher likelihood of infertility and other defects.
Conservation scientist Luke Dollar has said that any crossbreeding between big cat species is unethical and is the result of greed or irresponsible breeding.
“I can think of no legit excuse for a liger or tigon to exist,” said the program director for National Geographic Society’s Big Cats Initiative. “If we want to recognize and honour big cats, why would we possibly experiment in these completely unnatural and not biologically founded practices?”
Smaller cat species can and do interbreed in the wild. In the UK, for example, the Scottish wildcat (Felis silvestris) has become critically endangered partly due to interbreeding with domestic cats (Felis catus), which has seen a plethora of fertile hybrid cats replacing the pure wildcat across most of its range.
And dog species also seem to interbreed more readily in the wild, especially when it is hard to find others of the same species to reproduce with. In North America, coywolves are common where habitat loss and hunting has put pressure on wild populations of wolves and coyotes. The resulting animals have genes from both species and often those of domestic dogs as well.
Meanwhile as climate change means that grizzly bear and polar bear ranges now overlap, hybrids are increasingly seen and known as grolars (the result of a male grizzly mating with a female polar) or pizzlies (male polar with female grizzly).
