Inbreeding and Mobility Issues Doomed Saber-Toothed Cats Before Extinction
Saber-toothed cats became inbred–and struggled to move–before they went extinct
New research on Smilodon fatalis fossils from the La Brea Tar Pits reveals that population decline led to severe inbreeding. This genetic bottleneck caused a spike in spinal deformities and rare nerve tumors, crippling the cats' mobility. These physical ailments likely forced them to rely on trapped prey, accelerating their demise just before the end of the last ice age.
Your population's decreasing, and that leads to inbreeding, which makes you less able to respond to any kind of perturbation because you're losing that genetic diversity that evolution can play with.