In the eyes of the public, the sabre-toothed cat Smilodon ranks alongside Tyrannosaurus rex as the ultimate killing machine of all time. Powerfully built, with upper canines like knives, Smilodon has been portrayed as a fearsome predator of Ice-Age mammals such as mammoth, bison, and elk.
And while most scientists agree that the sabrecat was able to kill these animals thanks to its ferocious fangs, there has been plenty of debate about how it actually used them.
Now a new study, using a computer based technique called Finite Element Analysis (FEA), has tested some of the previous ideas about killing behaviour in Smilodon.
FEA is used by engineers to help design trains, planes, and cars, and allows them to digitally 'crash test' their designs to make sure they will work as intended. But biologists can use it to reverse engineer Nature's designs to find out what sort of forces a structure like a sabrecat skull was able to handle.
Skulls are much more complex then most man-made structures, and to apply the technique to a fossil big cat requires some tricks engineers don't usually have to handle, but an Australian team based at the University of Newcastle and the University of New South Wales have been working on a method to do just that and the results give scientists new insights into the behaviour of this iconic predator.
Compared to a modern day lion, the sabrecat had a relatively weak bite: for a ~230kg Smilodon the computer models predict a force of about 1000N (~100 kg) at the canines, about the same as the bite force of a 80 kg jaguar and a third of the bite force of ~250 kg lion.
In a Smilodon skull, the available area for jaw muscles is small compared to a lion, but to see if the sabrecat was somehow packing some extra bite in its cheek the team artificially increased the bite force to that of a 230 kg modern big cat.
The result: high stresses in the sabrecat's jaw (shown as greens, yellows, reds, and white in the model), far higher than in the lion. But if the extra bite force was supplied by the neck muscles instead (so that the sabrecat was driving its whole head - including the teeth - towards the prey) then it handles the forces much better. This suggests that the neck muscles played an important role in generating bite force in Smilodon.
But the real difference between the sabrecat and a modern lion is revealed when the models are subjected to the kind of forces that result from tackling struggling prey - prey that is still on its feet. Lions do this all the time, but when the Smilodon model was exposed to these forces it lit up like a Christmas tree. If there was one thing Smilodon was not doing, it was tackling unrestrained prey.
Sabrecats were well built for wrestling large prey to the ground, and the models show that it needed to do this before trying a bite. Moreover, the killing bite was most likely applied to the prey's throat, because it is easier to restrain the prey this way. It had to be made with care, but once the bite was done the prey was would have died almost instantly - a handy trick, when the predator needs to keep clear of angry herd-mates and hungry competitors.
A lion can take more than 10 minutes to kill a Cape buffalo - plenty of time for its mates to charge you, or the hyenas to arrive. On the other hand, lions can catch a wide range of different prey, including agile antelope and gazelle.
The sabrecat may have been a highly efficient hunter of large prey, but it was not built to catch smaller, faster animals and when the American megafauna went extinct at the end of the last Ice-Age the specialist predator went with them. This may explain why today we still have lions, tigers, and bears but no sabrecats.
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