Recent studies reveal that saber-toothed cats from the La Brea Tar Pits exhibited an unusually high number of spinal deformities, including rare spinal nerve tumors. These findings suggest that inbreeding may have contributed to the species’ vulnerability and eventual extinction.
Researchers have uncovered significant evidence of spinal nerve tumors within the fossilized remains of saber-toothed cats, suggesting a link to inbreeding as the species faced extinction. These tumors, linked to a specific genetic mutation, are known to cause severe pain and dysfunction, potentially driving the animals to seek easier prey.
Dr. Hugo Schmökel from the Evidensia Academy Sweden and the University of Zürich explained the predator’s plight: “A trapped prey animal is very attractive for a predator in pain. A wounded or sick predator must rely on carcasses for surviving, so they’ll take bigger risks to get to them.”
A Natural Trap
The La Brea Tar Pits in California, known for its pools of thick tar that ensnared numerous animals, became a death trap for many during the Pleistocene, including the saber-toothed cats, Smilodon fatalis. These predators, drawn by the cries of trapped prey, often met the same sticky fate.
Schmökel described the hunting behavior of these cats: “Smilodon was an ambush hunter, hiding in the lush vegetation of the late Californian Pleistocene, jumping on prey and wrestling it down, until a fatal stab ended the hunt. But scavenging certainly also happened.”
The preserved remains at the La Brea Tar Pits Museum provided ample evidence for scientists to examine the vertebrae of Smilodon. Out of 3,722 vertebrae from at least 849 adults, researchers noted numerous developmental abnormalities.
The analysis revealed 32 vertebrae with underdeveloped arches, 48 fused vertebrae, and 226 transitional vertebrae, where incorrect formation occurred. More notably, three vertebrae showed widened foramina, indicative of pressure from spinal nerve tumors.
Schmökel noted the implications of spinal tumors: “Dogs which are brought to my clinic with a spinal nerve tumor mainly have signs of pain, and many human patients with a spinal nerve tumor complain of pain. This was probably also the case in Smilodon. In advanced cases without treatment the nerve and the affected limb eventually lose function, making hunting very difficult.”
While spinal nerve tumors are exceedingly rare in both humans and modern animals, they were surprisingly prevalent among these ancient cats. The presence of three affected vertebrae suggests a rate of 353 cases per 100,000 Smilodons, starkly contrasting the human rate of 0.22-0.38 per 100,000.
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Genetic Bottleneck
The researchers propose that the high incidence of spinal abnormalities points to inbreeding, likely as the species’ numbers dwindled. This genetic bottleneck could have increased the prevalence of harmful mutations, akin to modern inbred populations of grey wolves.
Schmökel emphasized the broader implications: “Reduced fitness and smaller litters don’t help a population under stress. But inbreeding is not the cause of the crash of populations, it is a medical consequence. Loss of habitat, pollution, hunting or poaching, and in some areas today climate change, are the cause of the fall in numbers of wild cats. We can assume that the same happened to Smilodon at the end of the Pleistocene.
“We must take care of living wild animals. We humans reduce their living space, hunt them, pollute them. And when there are only a few left, we start, maybe, to act. But by then these animals are probably affected by inbreeding and saving them is more difficult.”
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