Ancient Predator's Painful Secret — Saber-Toothed Cats Were Falling Apart Before Extinction

HEADLINE: Inbreeding and Spinal Tumors Plagued Saber-Toothed Cats Before They Vanished ---

A Mighty Predator Brought Low From Within

They were among the most fearsome hunters the world has ever seen — apex predators armed with 20-centimeter serrated fangs and jaws that could open twice as wide as a modern lion's. But new research reveals that in their final millennia, saber-toothed cats were suffering from the inside out, their powerful bodies riddled with painful spinal deformities that may have sealed their fate.

A new study of more than 3,700 vertebrae from *Smilodon fatalis* found at Los Angeles' La Brea Tar Pits documents high rates of congenital spinal deformities and rare nerve tumors — conditions researchers link to sustained inbreeding as populations shrank near the end of the last ice age. The study was published on July 27 in *Frontiers in Veterinary Science*.

Tumors at a Staggering Rate

A spinal nerve tumor is rare enough that many doctors may go their entire careers without diagnosing one. It often causes pain first and, if left untreated, can slowly reduce function in the limb controlled by the affected nerve. In humans, it appears in an estimated 0.22 to 0.38 cases per 100,000 people and results from a genetic mutation, either inherited or spontaneous.

The rate was 1,000 times higher in the saber-toothed cat sample — at 353 per 100,000 individuals — and two of the three fossils bearing evidence of tumors date to 12,000 and 13,000 years ago, not long before the species went extinct. The abnormalities likely made movement painful and hunting difficult, pushing the giant predators to rely on easy meals like animals already mired in tar. In other words, the very reason so many of these cats ended up preserved in the tar pits may have been their deteriorating health — they were desperate, not bold.

The Genetic Downward Spiral

Scientists think that as the saber-toothed cat population shrank, fewer potential mates were available and pathogenic genes became more common. Similar spinal deformities are found in inbred gray wolf populations today, and skeletons and DNA dated to right before the disappearance of some now-extinct mammals — such as mammoths, woolly rhinos, and giant deer — also showed signs of inbreeding. In 2023, the same research team had already described high rates of bone disease in saber-toothed cat limbs, which may have also been caused by inbreeding.

*Smilodon fatalis* was slightly smaller than a modern African lion, weighing up to 280 kilograms, and roamed the grasslands, woodlands, and forests of North and South America during the Pleistocene epoch, which lasted from 2.58 million to 11,700 years ago. Lead study author Hugo Schmökel, a veterinary spine surgeon at the IVC Evidensia Academy in Stockholm, put it plainly: "Smilodon enjoys the reputation of mighty hunter. But the discovery of the tumor shows that it was an animal with weaknesses and feelings, not just a predator."

A Warning for Today's Wildlife

Schmökel is clear that inbreeding is not the root cause of a population's collapse — it is a medical consequence. Loss of habitat, pollution, hunting or poaching, and climate change are the cause of falling numbers of wild cats, and "we can assume that the same happened to Smilodon at the end of the Pleistocene."

The findings illustrate how shrinking populations can enter a cycle of genetic decline. "This might be how extinction happens," said researcher Balisi. The saber-toothed cat's story is not just a paleontological curiosity — it's a blueprint for what happens when a species is pushed to the genetic brink. With today's large predators facing mounting habitat loss and fragmentation, the bones locked in the La Brea tar carry an unmistakable message: by the time the physical damage becomes visible, it may already be too late.