Cats are known for being elusive and stealthy, but the southern tigrina takes those qualities to a new level. For decades, this South American feline has been hiding in plain sight, mistaken for a close relative called the tigrina or oncilla.

Physically, the two species are almost indistinguishable—both look like domestic cats with leopard-like spots. There southern tigrina is slightly darker than its north-eastern cousin, its spots are slightly larger, its tail is slightly shorter, and its ears are slightly rounder. But there’s more physical variation within each species than between them.

It’s their DNA that reveals the gulf between them. By analysing the genes of 115 “tigrinas” from all over Brazil, Tatiane Trigo showed those in the north-east are genetically distinct from those in the south and south-east, and the genetic differences between them are as large as those between other cat species. Although both tigrinas are found in central Brazil, some unknown barrier stops them from mating and they have not bred for some time.

Thanks to its genes, a second tigrina species has blinked into view, like a reverse Cheshire cat.

Trigo is assigning the classic name—tigrina (Leopardus tigrinus)—to the north-eastern cats, and she has named the others southern tigrinas (Leopardus guttulus).

These felines are the latest examples of cryptic species, where a single animal actually turns out to be two or more, largely thanks to genetic studies. There are two species of African elephants, two Nile crocodiles, and possibly many species of killer whales and giraffes.

Things get even more complicated when you consider two other small cats that live in South America. Geoffroy’s cat (Leopardus geoffroyi) is larger and stockier than the tigrinas, and its spots are solid dots rather than open rosettes. The pampas cat (Leopardus colocolo) is even more distinctive—it has stripes on its legs, pointed ears, and a shorter tail.

View Images Geoffroy’s cat. Credit: Charles Barilleaux.

Trigo showed that some of the genes in the tigrinas (but not the southern ones) came from the pampas cats. Although the two species don’t mate any more, they must have hybridised at some point in their history. This may have been important for the tigrinas. Unlike their forest-dwelling southern cousins, they live in open plains… and so do the pampas cats. Maybe they gained important adaptations for life in the open after their ancestors bred with plains specialists. “This is an intriguing possibility in this case, and we plan to further investigate it,” says Trigo.

The team also found that Geoffroy’s cat is still hybridising with the southern tigrinas! Southern Brazil, where the two species overlap, is effectively a “hybrid swarm”—a zone where almost all southern tigrinas and Geoffroy’s cats are partial hybrids of the two.

So, do they still count as separate species? Trigo thinks so. Their genes tell a story of separation and reunion. The two cats did properly split off from each other some time ago. But after the last Ice Age, the southern tigrinas experienced a population boom, and started expanding into southern Brazil where they met up with their long-separated Geoffroy’s cat cousins. They bred, and their offspring are clearly fertile. But there are still strong genetic differences between the two cats in parts of their range outside the contact zone. They’re not going to merge back into a single species.

Trigo’s priority now is to find out more about the north-eastern tigrinas, which have been poorly studied compared to their southern kin. How does it live? How many are there? Is it in need of protection? “There are still many secrets to be learned from biodiversity, including cryptic species in groups that are thought to be well-known, such as wild cats,” she says.

The team are now planning to study other South American cats, like the ocelot and margay. They’ve already found some interesting genetic divisions within both species throughout their range, although nothing definitive yet. On the flipside, they’ve found some evidence that the pampas cat is not, as others have suggested, two or three distinct species.

Reference: Trigo, Schneider, Oliveira, Lehugeur, Silveira, Freitas & Eizirik. 2013. Molecular Data Reveal Complex Hybridization and a Cryptic Species of Neotropical Wild Cat. Current Biology http://dx.doi.org/10.1016/j.cub.2013.10.046