In my previous post I commented on how it could take you months to make sense of what you observed during just a few days out in the African bush. Well, that was an understatement. It can be years before something you saw in the wild finally seems to click in your “scheme of things”. Or may be it is just that I am a slow learner.
A few years ago I was awed to watch a cheetah killing a gezelle in the Ndutu area of Tanzania. I had seen this drama many times in documentaries, but seeing it in front of my eyes not only was breathtaking: it confirmed the strange sensation that these cats are a bit awkward about handling their prey. Of course there was nothing awkward about the way this amazing cheetah mother caught the gazelle in the blink of an eye, dispatched it in a few minutes, and provided a most welcome meal for its hungry cubs. And yet…
Back home I compared the footage of the cheetah kill with that of a leopard kill I had witnessed the previous year in Samburu reserve, Kenya. Still something felt un-catlike in the way the cheetah killed, but what could it be? In fact, the cheetah’s killing bite is extremely efficient and takes the adaptation of felines for strength and precision one step further. A short muzzle and extremely powerful jaw-closing muscles imply that the cat can sustain its bite for many minutes until the prey dies of asphyxiation. Actually the leopard kill I saw was less orthodox in that the cat was biting at the muzzle, not the throat of its prey. And yet…

Early pencil strokes of my sketch of the Ndutu cheetah with its gazelle prey. Something un-catlike was afoot, but I couldn’t put my finger on it…
killing bite sektch 1 a

More recently I went through the footage again, and suddenly I realized what was bothering me. The way the cheetah was holding its prey made it look like it didn´t know what to do with its paws. In fact it was just resting its front paws on top of the prey, much as a dog will do when possessively chewing a large bone. In contrast, the leopard I filmed at Samburu held its prey’s head firmly between its paws, a fitting embrace for such a “kiss of death”. Actually, this difference made a lot of sense from an anatomical point of view -and gives me further insights into sabretooth behaviour.

My sketch of the cheetah with the gazelle takes shape. Here the combination of cat-like bite and dog-like hold is evident
killing bite sektch 1 c

“What do sabretooths have to do with this?”, you may ask. Let me explain. The key difference between the cheetah and the other big cats in terms of how they handle their prey is the morphology of their forelimb bones, especially the elbow and wrist. A few million years ago, the cheetah’s ancestors had paws more like those of a leopard or a cougar. But as the cheetah lineage became more adapted for speed, the elbow lost part of its ability to rotate the forearm, and the wrist and hand became more narrow and less flexible. The forelimb of the cheetah was becoming better adapted to move exclusively in the vertical plane, while losing extra weight in the form of muscles that rotate the paw… in other words, it was becoming more similar to that of a dog than to that of its own feline relatives. As a result, the cheetah can’t use its paws as efficiently as the leopard for holding its prey during the killing bite. That is one more reason why the cheetah sticks to relatively small prey. And that is one reason why the cheetah is a much poorer climber than the leopard is!

In this “X-ray sketch” I show the position of the bones inside the cheetah’s body as it holds its prey. The front paw rests on the prey much as a dog’s would do
killing bite sektch 1 d

In contrast, the paws of the leopard supinate freely in order to hold the impala’s head firmly for the “kiss of death”
samburu leopard impala 1 c

Concerning the sabretooths, there was also a diversity of forelimb morphologies among them. Robust smilodontins like Smilodon or Megantereon had powerful and well-muscled fore-paws with fearsome retractable claws, well able to rotate in any direction and to hold large prey immobilized in any position. But members of the genus Homotherium had lost part of those adaptations in order to become more efficient runners. The wrist of Homotherium was much narrower than those of smilodontins, more restricted to rotation in the vertical plane, and its claws were smaller and less fully retractable, except for the huge dewclaw -something not unlike what we see in the cheetah.
Of course Homotherium was no cheetah. It was a lion-sized sabretooth cat with enormously strong forelimbs, whose mere body weight could help it control prey animals the size of a horse. But still the way it handled its prey would be somehow different to how the hyperrobust Smilodon did. Careful observation of the behaviour of modern big cats can still throw new light on how to reconstruct their extinct relatives.

In this illustration from my book “Sabretooth” you can see Homotherium using its body weight to pin down its horse prey, but still not quite “embracing” its neck for the killing bite

Posted on 14/10/2015, in Uncategorized. Bookmark the permalink. 2 Comments.

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