When Snow Leopards Reached Portugal

While the various species of "roaring cat" all share a great many points of similarity, most are easily distinguished from each other. Arguably, one of the most distinctive is the snow leopard (Panthera uncia). Not only does this have unusually thick fur for a wild cat, but it also has a longer tail than we would expect, and the face is shorter and wider than that of other roaring cats.

The snow leopard was first scientifically described by Johann Schreber in 1775 as a member of the genus Felis. The differences from other cats were sufficient that, in 1854, John Edward Gray proposed that it be given its own genus, Uncia. His original definition of the genus did not stand (it also included at least one species of "purring cat"), but it was resurrected again in the early 20th century, and used solely for snow leopards up until 2006. In that year genetic evidence placed it alongside the other "roaring cats" in Panthera, something that has been amply confirmed since.

Snow leopards have thick fur because they live in a particularly cold environment. They are found only in central Asia, from the Himalayas in the south to southern Siberia in the north, a region that takes in many countries. Significantly, however, they are found almost exclusively in mountain ranges above 3,000 metres (9,800 feet) elevation, where it is typically too cold for trees to grow. In the northern parts of their range, where even the lowland climate becomes cold, they can be found as far downslope as 600 metres (2,000 feet) but this is very much an exception. 

As one might expect, this limits their ability to move further afield; for them, the mountains of Central Asia might as well be a large island, with the lowlands as much a barrier as a sea. This makes climate change a particular problem, as suitable habitat retreats further and further up the mountainside and, given the shape of mountains, shrinks in the process. 

In addition to the fur, it seems reasonable to assume that the other points of difference between snow leopards and other big cats are also due to their unusual habitat. For example, the short, wide face with its domed forehead resembles that of a cheetah (a "purring cat") more than it does that of its close relatives, and, just like a cheetah, the skull has a large frontal sinus. In the case of cheetahs, this sinus is thought to help improve respiratory efficiency, dissipating heat when the animal is running fast. Snow leopards are not fast runners, even compared with lions, let alone cheetahs, but for them, the sinuses may help to warm the air they breathe in. Equally, a general improvement in respiratory efficiency may well be helpful for an animal that habitually lives at high altitudes where the air is thin.

It has also been suggested that the cheek teeth of snow leopards are adapted to chewing tough, partially frozen meat, since they tend to stay with the carcasses of their prey for longer than other big cats (presumably because finding anything to eat where they live is a bigger achievement than it is for predators in, say, the Serengeti). The shorter jaw and the arrangement and size of the relevant muscles probably gives snow leopards a stronger canine bite than regular leopards have, which may help in biting down on the relatively thick bones of their favoured goat prey rather than the slender bones of gazelles. The shape of the face would also give them better stereo vision than other "roaring cats" which may help in picking out goats from the open rocky background - apart from fast-running cheetahs, similarly strong binocular vision is seen in some small cats that live in open environments, such as manuls.

Away from the head, the long tail of snow leopards likely gives them better balance, something that's also going to be useful on steep, craggy, mountainsides. An unusually flexible lower back and elongated lower limbs enhance the snow leopard's ability to pounce, which, again, may help on rugged terrain.

Some of these differences are subtle, and many of the interpretations of their purpose given above are speculative rather than definitively proven - snow leopards have not been so well studied in the wild as lions or tigers. But they do exist, and this raises the question of when and how they first evolved, something that might also give us some idea of how accurate those interpretations are.

We now know, from genetic evidence, that the closest living relative of the snow leopard is the tiger. The same genetic studies also tell us that the last common ancestor of tigers and snow leopards probably lived around 2 million years ago. That's about the time that the Ice Ages started. Which, let's face it, doesn't sound like a coincidence when we're talking about an animal that likes cold, treeless, terrain.

Proposed tree - note that many others
place the leopard closer to the lion

Trying to identify exactly what happened during those two million years is a daunting task. Very few fossils have been specifically identified as belonging to snow leopards, and those that have are mostly very recent. In 2014, a 4 million-year-old fossil from Tibet was identified as a possible snow leopard ancestor, but, not only does this seem rather too far back, but more recent analysis has confirmed that it doesn't belong to Panthera at all, but to a now-vanished genus of pantherine cats.

A few weeks ago, however, researchers published a study in which they examined five fossils that could potentially be connected to snow leopards. They concluded that all five belonged to animals more closely related to the snow leopard than to anything else alive today and, moreover, that they showed a neat stepwise progression towards the modern form, with each fossil being closer than the next oldest one.

The most recent, from Niuyan cave in China, had already been identified as a snow leopard, and the new study confirms that it's essentially indistinguishable from the modern animal. Niuyan is less than 1,000 metres (3,300 feet) above sea level and so too low for snow leopards today, but, not only do we know that the animals can venture to lower altitudes in cold climates, but the fossil does date from towards the end of the Last Ice Age when that would have been easier than it is now.

The next oldest fossil, which doesn't date back much further, is not from Central Asia at all. Rather, it comes from central Portugal, about 90 km (55 miles) north of Lisbon. Originally supposed to belong to a leopard, the new analysis of the nearly complete skull describes it as belonging to a previously unknown subspecies that the researchers have christened the Portuguese snow leopard (Panthera uncia lusitana). It's the only fossil subspecies known, and, for that matter, debate continues today as to whether there are two, three, or no living subspecies of the animal.

The other three fossils are, however, different enough that the authors conclude they represent now vanished species. One of the three, found in a cave near Perpignan in southern France, had previously been identified as a snow leopard subspecies, although the new study argues that the differences are sufficient to raise it to species level as the Pyrenean leopard (Panthera pyrenaica). It's about 600,000 years old, making it the second oldest of the five fossils examined and more closely resembles a regular leopard, lacking the enlarged cheek teeth and unusually short face of living snow leopards.

The remaining two fossils don't have species names yet and conceivably never will if later researchers conclude that they aren't as different from other specimens as this study suggests. The oldest is another leopard-like animal, dating back over 2 million years to almost the point that the lineage is thought to have diverged from that of tigers. Significantly, it's not European, but Chinese.

Taken together, this implies that the earliest ancestors of snow leopards (as distinct from their common ancestor with tigers) evolved in the general area of present-day Tibet, and that they probably already fed on goats, which themselves originated in Tibet around this time. As the Ice Ages came and went, opportunities developed for these early goat-eating predators to follow their prey across the rugged highlands to the west, ultimately reaching the Pyrenees.

A remarkably rapid burst of evolution then followed, developing almost all the unique features of the modern snow leopard in less than half a million years. A later burst of icy climate saw the now literal snow leopards reach as far as the snowy hills of Portugal before the arrival of the modern Mediterranean climate forced them to retreat back to their original homeland. 

[Photo by Eric Kilby, from Wikimedia Commons. Cladogram adapted from Jiangzuo et al. 2025.]