What's the difference between a leopard and a jaguar?

A large predator lurks in the brush, flashing a long tail and fur printed with telltale black and tan rosettes. It must surely be a leopard. Or … could it be a jaguar? With their stealthy hunting habits and similar builds, patterns and hues, the two large cats can be strikingly difficult to tell apart. What, in fact, is the difference between a leopard and a jaguar?

To begin with, they live in completely different parts of the world, with jaguars found in the Americas today, and leopards occurring across a large range spanning Africa, parts of the Middle East and Asia.

"They're on the opposite sides of the globe, but a long time ago they shared a common ancestor," Allison Devlin, jaguar program director for Panthera, the global wild cat conservation organization, told Live Science.

Jaguars and leopards are part of the Panthera genus, which also includes lions, tigers and snow leopards. Tigers and snow leopards form their own branch of the Panthera family tree, while leopards, jaguars and lions are grouped together on another branch because they descend from a separate common ancestor.

However, between 3.6 million and 2.5 million years ago, jaguars split from the common ancestor shared by their leopard and lion cousins. The origins of the Panthera genus are uncertain, but fossil evidence shows that jaguars dispersed across the Eurasian plateau about 2 million years ago, and from here they migrated across the Bering Land Bridge during the last ice age to North America, and eventually down into Mexico through South America, where this species occurs today. In fact jaguars are the only Panthera lineage that occurs in the Western Hemisphere, and exist as just one species across their entire range, Devlin said.

Meanwhile, leopards split off from their closer relatives, lions, about 2 million years ago, and spread into Africa, Southeast and Northeast Asia, where they occur as eight regional subspecies across this range today. This evolutionary history means that leopards and jaguars are different species that aren't even each other's closest relative, despite their striking similarities.

Most noticeable among these common features is their spots, but even these have subtle differences that can be used to tell the animals apart.

"The rosettes on the jaguar quite often have spots in the middle of them, whereas the leopard doesn't," Tara Pirie, a lecturer in ecology and conservation at the University of Surrey in the U.K., told Live Science. She shared another clue: "[Leopard] rosettes are tightly packed, whereas the jaguar, with the spot in the middle, their rosettes are quite large and not as tightly packed."

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Their shared ancestry might partly explain why these two remote species both have spots. But it could also be an adaptive response to the environments they live in, a phenomenon known as convergent evolution, Devlin explained.

Rosettes, spots and other light-and-dark mixed patterns are in fact quite common in felid predators that live in partly-shaded landscapes, where their spots help keep them camouflaged. Jaguars and leopards both occur in places with partial forest cover, and both animals also rely on ambush tactics to hunt. So their coats provide critical camouflage enabling them to sneak up and pounce on prey at close range, Devlin said.

There are, however, some key differences in their hunting styles that also reveal striking physiological distinctions between the two animals.

"The way I think of it is that a leopard is built more like your all-around athlete. They can climb trees, they can run, they can ambush," Devlin said. "For jaguars, they're built more like a bodybuilder, where they're heavier in the barrel, in the chest and in the head. And part of that is related to their hunting techniques."

Jaguars are real heavyweights that can reach up to 260 pounds (120 kilograms). Their generally stockier frames include a much bulkier head than leopards have, formed by larger bones that support bigger muscles and give this animal some of the strongest jaws in the cat family, Devlin said.

Whereas most cats kill their prey through strangulation or breaking the neck, the jaguar's powerful bite gives it the extraordinary ability to kill its prey by puncturing the skull. Their bite is so strong that they can crush through the upper shells of tortoises and sea turtles, both of which they target as prey, Devlin explained.

On the other hand, at a much lighter 176 pounds (80 kg), leopards kill prey through suffocation, by biting the throat. Their smaller frames allow them to spring up into trees — something that jaguars can also do, although in general they spend far less time in trees. The leopard's arboreal preferences, meanwhile, have given them the advantage of being able to store or "cache" prey away from others' prying eyes, Pirie said.

Up in the canopy, the leopard's nimble-footed ways are helped along by another key tell that separates them from jaguars: a lengthier tail. "Whereas in the leopard, it could be up to a meter [3.2 feet long], in the jaguar it is maybe 60 centimeters [1.9 feet]. So even just that 40 centimeters [1.3 feet] could bring a lot more balance," Pirie said.

With these features as a guide, it's just about possible to tell leopards and jaguars apart. But nature has one more trick up her sleeve: all-black leopards and jaguars. The satiny sable coats on these animals are caused by a genetic mutation, and while they might look like it, they are not a different species. In fact, they're what's known as the "melanistic phase" of the species in each case, according to Devlin.

Interestingly, in both leopards and jaguars, these darker cats appear more commonly in heavily-shaded habitats. Black jaguars occur more in the dimly-lit depths of the Amazon rainforest, Devlin said.

Meanwhile "you've got leopards over in [the Malaysian jungle], they tend to be melanistic … which would help blend them in with that dense habitat," Pirie said.

The rarity of melanistic leopards and jaguars makes them even more vulnerable than their regularly-spotted siblings, who are threatened by hunting, shrinking habitats and the illegal wildlife trade. As a result, jaguars and leopards share the unfortunate fact that their populations are both in decline, according to the International Union for the Conservation of Nature.

But we have the tools to change that, Devlin said. "If they have the habitat, the prey and the protection that they need, they can persist."