Can fossil skulls tell us if sabretooth cats purred or roared?

A team of researchers has set out to work out if sabretooth cats roared like lions or purred like domestic cats.

Fossils give tantalising clues as to how animals that lived thousands or millions of years ago might have looked, but is often subject to debate.

Even more difficult to say is how prehistoric creatures sounded. Some clues about ancient animal vocalisations can be found in their fossilised remains.

Modern cats are split into two groups.

Pantherine, “big cats,” roar – lions, tigers, leopards and jaguars.

Felinae, “little cats,” purr – lynxes, cougars, ocelots and domestic cats, and even some larger cats, such as cheetahs, cannot roar.

While they can produce a variety of different vocalisations including meows, yowls, snarls, cries and “chuffs” which are non-threatening sounds unique to tigers, today’s cats are found in one of these two main groups: roarers or purrers.

But what about extinct cats? In particular, what about the most famous extinct cat, the sabretooth cat?

This animal, also called Smilodon and incorrectly referred to as a sabre-toothed “tiger,” was a large, powerful and fearsome hunter. It lived in the Americas from 2.5 million years ago to as recently as about 10,000 years ago.

Smilodon populator was the largest species of the genus and lived in South America. It is estimated that it could grow to 220–440 kg, making it heavier on average than lions and tigers today. It’s trademark incisors could grow to be more than 25 cm in length.

One might imagine that such an imposing creature must have roared. But an analysis of Smilodon skull fossils by North Carolina State University researchers has shown that it may be more nuanced.

The research is published in the Journal of Morphology.

“Evolutionarily speaking, sabertooths split off the cat family tree before these other modern groups did,” says corresponding author Professor Adam Hartstone-Rose. “This means that lions are more closely related to housecats than either are to sabertooths.”

“That’s important because the debate over the kind of vocalization a sabertooth would have made relies upon analyzing the anatomy of a handful of tiny bones located in the throat,” Hartstone-Rose says. “And the size, shape and number of those bones differ between modern roaring and purring cats.”

While it is soft tissues (which don’t usually fossilise) in the throat that drive vocalisation, anatomists have noticed that the hyoid bones which anchor those tissues in place differ between purring and roaring cats.

“Because sabertooth tigers only have seven bones in their hyoid structure, the argument has been that of course they roared,” Hartstone-Rose says. “But when we looked at the anatomy of modern cats, we realized that there isn’t really hard evidence to support this idea, since the bones themselves aren’t responsible for the vocalisation. That relationship between the number of bones and the sound produced hasn’t ever really been proven.”

The researchers compared the hyoid structures of 4 modern roaring cat species, 9 living purring cats and 105 fossil hyoid bones from Smilodon.

Smilodon hyoid anatomy is “weird,” Hartstone-Rose says. “They’re missing extra bones that purring cats have, but the shape and size of the hyoid bones are distinct. Some of them are shaped more like those of purring cats, but much bigger.”

Because sabretooths had much larger hyoids, they may have had a deeper vocalisation than even lions and tigers.

“If vocalization is about the number of bones in the hyoid structure, then sabertooths roared. If it’s about shape, they might have purred. Due to the fact that the sabertooths have things in common with both groups, there could even be a completely different vocalization.”