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Journalism of Courage
Saber-toothed tigers must have been truly intimidating predators when they walked the Earth millions of years ago. But there is an important question that might determine the scale of how intimidating they would have been to us when humans coexisted with the big cats—do they roar or do they purr?
The answer to that is a little more complicated than you may think. A new study published Sunday in the Journal of Morphology sets out to explore the data behind both possibilities—that of the cats purring and that of the cats roaring.
Felidae is the name given to the family of carnivorous animals that we refer to as cats. Modern cats typically belong to two subfamilies—Pantherinae or the “big cats” who can roar, including lions, tigers and jaguars and Felinae or the “little cats” who can purr including cheetahs, cougars and domestic cats.
“Evolutionarily speaking, sabertooths split off the cat family tree before these other modern groups did. This means that lions are more closely related to housecats than either are to sabertooths,” said Adam Hartstone-Rose, corresponding author of the study, in a press statement. Hartstone-Rose is a professor of biological sciences at NC State.
The debate over whether sabretooth tigers used to roar or purr relies on a small group of tiny bones located in their throat, according to Hartstone-Rose. The size, shape and number of these bones are different between the modern roaring and purring cats.
The bones themselves do not really drive vocalisation, instead, the larynx and soft tissue in the throat play an important part there. But anatomists noticed that the bones responsible for anchoring those tissues, called the hyoid bones, differed in size and number between the two kinds of modern cats.
“Because sabertooth tigers only have seven bones in their hyoid structure, the argument has been that of course they roared. 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,” Hartstone-Rose added.
To explore that relationship, the researchers examined the hyoid structure of four roaring cat species: lions, tigers, leopards and jaguars, along with five purring cat species: cougars, cheetahs, caracals, servals and ocelots. They then compared this to 105 hyoid bones from the famous sabetrtooth tiger Smilodon fatalis.
“You can argue that since the sabertooths only have seven bones they roared, but that’s not the whole story. The anatomy is weird. 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,” explained Hartstone-Rose.
If the missing bones were the key to different vocalisations, the bones that are most closely connected to them should look different between the groups. But those bones look very similar in shape whether they came from purring or roaring cats, according to the researchers.
“We found that despite what history has told us about the number of bones in the hyoid structure, no one has validated the significance of that difference. If vocalisation 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,” added Hartstone-Ross.
According to Ashley Deutsch, lead author of the research, it is more likely that the size of the hyoids play a role in the pitzh of the vocalisation. Smilodon was not as large as the largest modern cats but its hyoid bones are substantially larger than those of any of their living relatives. So there is a chance that their vocalisations were deeper than that of tigers and lions.
