Thursday, July 18, 2013

Giant theropods will NIBBLE YOU TO DEATH

Sorry for the lack of updates for a while, everyone! I've been keeping busy with summer class and work, but now I finally have a bit of free time and will start writing again.

More often than not, the fossils of truly gigantic sauropods are found in the same formations as equally gargantuan theropods. There is no doubt that these predators fed on sauropods once in a while but, being extinct and all, it's extremely difficult to determine just how they fed. Most depictions show allosaurs and carcharodontosaurs leaping onto the backs of unsuspecting saurpods, or clamping their toothy jaws around the herbivore's neck.

When the sizes of contemporary sauropods and theropods are compared, we notice something: sauropods were friggin' HUGE. Even those theropods which are theorized to have been pack-hunters would struggle with taking down an adult super-sauropod. Of course, this doesn't mean that the carnivores were forced to starve; there were plenty of smaller, more easily-subdued critters to eat. Facing an animal which weighed as much as an entire herd of elephants could not only fail, it poses a serious risk of injury and even death to the hunters. How, then, could a predator get a taste of sauropod without risking fatal injuries?

The contemporary giants Tyrannosaurus rex and Alamosaurus sanjuanensis. You can see that, as big as T. rex was, the sauropod is tremendously bigger.

Welcome to the wonderful world of flesh-grazing!
The cookiecutter shark is a species of shark which barely reaches 2ft in length. However, its main prey includes animals which are monumentally larger than it is, including, among other things, whales, seals, dolphins, tuna, and other large sharks. How does such a tiny creature eat such big meals?

It manages to do so because it doesn't prey upon the entire animal. The cookiecutter shark rasps small plugs of skin from its prey, which not only provides it with a meal, but also leaves the rest of the animal alive for repetetive feedings. If you think about it, killing an animal which is much larger than yourself is not only dangerous, it is wasteful: if an allosaur was to take down a giant sauropod by itself, there is no way it could eat the entire animal. Even a pack would leave remains, which would be picked up by other carnivores or simply left to rot.

Even the modestly-sized (for a sauropod) Camarasaurus may have been a bit too much to handle for an adult Allosaurus.

Recent analyses of theropod skull biomechanics show that even large predators had relatively fragile skulls. In a recent post, I summarized a study of Allosaurus feeding mechanics which showed that the animal fed with rapid, jerking motions of its head like a modern falcon. A previous study, concerning Allosaurus' "hatchet" method of feeding, showed that running agape directly at the side of a giant sauropod would not only inflict minimal damage to the sauropod, it would break the jaw and possibly the neck of the Allosaurus.  The hatchet-like hunting method would be much more effective on smaller animals.

Even Tyrannosaurus displays certain features of its skull which indicate rapid, birdlike head motions. Perhaps, as these giants ran alongside titantic sauropods, they could quickly strip morsels of meat from the sides of their prey and run off unnoticed. This would not only leave the prey alive for future feedings, it would greatly reduce the possibility of risk or failed attacked by the predators.

The Case of the Leaping Acrocanthosaurus
Fossilized footprints from the carcharodontosaur Acrocanthosaurus atokensis are particularly well-known throughout Texas, where it once dwelled beside the super-sauropod Sauroposeidon proteles. One preserved trackway shows the footprints of the predator trailing a dozen or so of these sauropods, and in one segment of the track, the Acrocanthosaurus appears to have leaped onto the side of one of them. However, the tracks of the sauropod do not appear to change in speed or direction, suggesting that the predator did not hang onto the herbivore for very long, if at all.

As if the Tyrannosaurus/Alamosaurus comparison wasn't startling enough, there's a snowball's chance in Hell that a lone Acrocanthosaurus could ever take down an adult Sauroposeidon. The possible "attack" footprints are shown below the skeletals.
Perhaps this is evidence of Acrocanthosaurus not viciously attacking Sauroposeidon, but simply snagging a strip of meat from its side before parting from the herd. It is certainly much more plausible than an Acrocanthosaurus actually bringing down one of the giants, especially when the sizes of both animals are compared...

Being an apex predator means that you have the size and tenacity to eat basically every bit of flesh in your environment. None of these giant theropods would have had trouble finding something to eat. The question at hand is whether or not they were bold enough to tackle such monumental prey as the biggest of the sauropods, or whether their main quarry were smaller animals. And, while sauropods could certainly fend for themselves, it is very possible that unnoticed bits of muscle and skin could be torn off once in a while.

1 comment:

  1. Meat grazing is a suicidal attempt IMO, because it will make the theropod to come close to the sauropod's body and ensure the sauropod to attack (tail/neck swipe, kick) it