Origins of....Species (Life Sciences)

[Mick Harper]

They are trained only to attack egregiously wicked people. Repeatedly, every day.

[Rocky]

[Hatty]

[Chad]

[DPCrisp]

To remind you of an earlier exchange in this thread:

[DPCrisp]

Despite being more powerfully built than other large cats, Smilodon actually had a weaker bite. Modern big cats have more pronounced zygomatic arches, while Smilodon had smaller zygomatic arches which restricted the thickness and therefore power of the temporalis muscles, and thus reduced Smilodon's bite force. Analysis of its narrow jaws indicates that it could produce a bite only a third as strong as that of a lion. There seems to a be a general rule that the saber-toothed cats with the largest canines had proportionally weaker bites.

So why the comparison with big cats and big prey? Since when do megafauna not take a lot of chewing?

{I think I thought of this when Madagascar was on: where the sabre-tooth had the usual cartoon feline cheekbones.}

In addition, Smilodon could open its jaws 120 degrees, whereas the lion can only open its jaws to 65 degrees. It has been suggested that Smilodon's smaller temporalis muscles (controlling much of the bite force) was not used in the killing of prey, but rather, the immense strength of the neck of Smilodon allowed it to stretch its jaws around the throat and press its canines into the prey with the usage of such immense neck and forelimb muscles rather than an actual bite

That's alright if you must persist in the big game analogy, but the evidence for it appears to be scant.

The social pattern of this cat is unknown. It has been suggested, based on the abundance of S. fatalis fossils in proportion to prey animals trapped in the La Brea tar-pits, that they were packs of scavengers, lured in by the distress calls of trapped prey.

Big game you have to wrestle and drag out of the tar? That's a perfect match for the sabre-tooth's physique. They must have evolved there. Except, that doesn't explain their presence throughout the Americas. Let's not get too bogged down in just the most famous site...

If the skeletons in the tar are not representative of the expected hunter-to-prey ratio, they must mean the sabre-tooths were disproportionately stupid: they had to be attracted in from extra far away, even though they routinely died in the process.

If they didn't hafta come extra far, the tar-pits must have contained the mix of sabre-tooths and other megafauna in the area. If the proportion is too high, isn't that evidence that they were not big game hunters? Never occurred to anyone that the sabre-tooths went in the water -- I mean the tar -- for exactly the same reason as everyone else: to drink, to find something to eat.

This possibility was tested in 2008 by Chris Carbone (of the Zoological Society of London), who documented the responses of African predators of the Serengeti and Kruger National Park to recorded distress calls of prey species; it was determined that playbacks of prey sounds attract social carnivores, but not solitary hunters.

Well, duh.

Additionally, some fossils show healed injuries or diseases that would have crippled the animal. Some palaeontologists see this as evidence that saber-toothed cats were social animals, living and hunting in packs that provided food for old and sick members

Is any other social hunter known to look after "unwanted"/unproductive members of the group like this? Quite the opposite, surely.

But being crippled is only a problem for an athlete. But how athletic do you have to be to forage, and maybe stand your ground against the odd predator, using your powerfully built adductor muscles?

[DPCrisp]

Smilodon probably preyed on a wide variety of large game including bison, deer, American camels, horses and ground sloths. As it is known for the saber-toothed cat Homotherium, Smilodon might have killed also juvenile mastodons and mammoths.

[Cut to Homotherium]

Friesenhahn cave in Texas contained the remains of over 30 H. serum individuals, which were discovered along with the remains of between 300 and 400 juvenile Columbian Mammoths. Besides mammoth, very few other potential prey species were found in the cave - it is therefore unlikely that Homotherium carried scavenged carcasses of already dead animals to the cave. Such specialization on prey of a particular species and age structure is not covenant with a scavenging lifestyle. For the same reason it is also unlikely that the dire wolves carried the mammoths into the cave.

Doesn't say what else there was that they discount as potential prey. Doesn't say how we know Homotherium wasn't there for the very same reason as the mammoths. Doesn't say why so many cats were expected to die at the dinner table. Doesn't say how we know dire wolves (or humans or...?) didn't carry all the carcasses into the cave.

Lo and behold:

The worldwide association of Homotherium species with proboscidean (elephant and mastodon) and rhinoceros remains, mainly those of juveniles, suggests that Homotherium preyed selectively on these tough-skinned animals

Or that they were eating much the same things or in much the same way or in much the same places!?

In North America fossil remains of Homotherium are less abundant than those of its contemporary Smilodon... Reduced claws, relatively slender limbs and the sloping back indicate adaptations for endurance running in open habitats.

Hmm. OK, maybe we're seeing dry/land/other-adaptations coming in.

[DPCrisp]

[Back to Smilodon]

Modern big cats kill mainly by crushing the windpipe of their victims, which may take a few minutes. Smilodon's jaw muscles were probably too weak for this and its long canines and fragile skull would have been vulnerable to snapping in a prolonged struggle or when biting a running prey.

Fragile skull? So much for powerful neck muscles driving the canines home. Tell you what though: you get a strong neck from hanging your head to dig and grub about all day.

Research in 2007 concluded that Smilodon more probably used its great upper-body strength to wrestle prey to the ground, where its long canines could deliver a deep stabbing bite to the throat which would generally cut through the jugular vein and / or the trachea and thus kill the prey very quickly.

So how many had their teeth snapped off by kicking, butting, struggling prey?

The leaders of this study also commented to scientific journalists that this technique may have made Smilodon a more efficient killer of large prey than modern lions or tigers, but also made it more dependent on the supply of large animals. This highly-specialized hunting style may have contributed to its extinction, as Smilodon's cumbersome build and over-sized canines would have made it less efficient at killing smaller, faster prey if the ecosystem changed for any reason.

Yes, yes. Paradigm buttressing.

Smilodon became extinct around 10,000 BC... North America began to dry out...

So the evidence is that there was no shortage of wetlands when the sabre-tooths lived there? Thank you very much.

[Chad]

I really like this idea... even more than my own (previously undisclosed) notion that sabertooths must have been hematophagic.

Take a look at this lion skull:



After killing its prey the lion then has to remove the flesh... Those side teeth provide the perfect scissor action for this, while the canines are not too intrusive to prevent effective butchery.

Now compare the Smilodon skull:



(Don't forget that it was supposed to be devouring bigger tougher prey than the lion.)

Dan has already told us that Smilodon had a more fragile skull than the lion and a less powerful bite... and just take a look at its dentition... totally unsuited to cutting flesh from a carcass.

[Ishmael]

So what did it eat? I'm not following. Insects? Salmon? Rudabegas?

[Chad]

Well, felids require a higher proportion of their diet to consist of animal protein than any other carnivore... and in the absence of any evidence of a specialised digestive system; we must assume this applied inclusively to Smilodon (which rules out a diet of rudabagas).

But a highly specialised dentition usually indicates a highly specialised diet (I haven't yet totally given up on the idea of a hematophagic diet)... but I really don't think those teeth were well suited to chomping up megafauna, despite what orthodoxy would have us believe.

Those sabre teeth and all that upper body strength would make short work of termite mounds or rotting logs... or maybe they had a similar diet to the equally toothy walrus (which would fit with Dan's observations):

[Ishmael]

What about thick skinned prey? Would you not need long teeth?

[Chad]

If you were part of a lineage of generalised, big game hunting cats which had decided to specialize in killing and devouring very large, thick skinned megafauna... and you made up a wish-list of improvements to the tools of your trade, it may look something like this:

1) Longer canines: to penetrate thick skin of prey. (But not so long as to hinder butchery.)
2) More efficient shearing teeth: to remove thick skin and flesh from carcass.
3) More powerful bite: to cope with extra demands of devouring megafauna.
4) More robust skull: to cope with increased risk of trauma.

Poor old Smilodon unfortunately didn't get many of his wishes... His canines may be longer, but are rather cumbersome when it comes to actually eating large prey... his shearing teeth, rather than being more efficient, are fewer in number... his bite is weaker rather than more powerful... and his skull is more fragile rather than more robust.

Back to the drawing board... (Or choose a different diet.)

[Ishmael]

[Chad]

Personally, I'm simply arguing what it wasn't rather than what it was... but I don't think it was a vegetarian any more than I think it was a big game hunter.

I would like to hear more of Dan's thoughts on the matter.