The Problem Of Tiny Allosaurs And Big Apatosaurs

Hello again, readers! This is where we get to the “dinosaurs” part of the blog title.

I was rereading Gregory S. Paul’s work Predatory Dinosaurs Of The World this afternoon. It is a lovely book published in the late 1980s, with first-rate illustrations and an excellent means of engagement with the reader. In it, he ellaborates on an interesting problem: The scale of hunting in the Jurassic period. I don’t doubt that many have arrived at my conclusion to this problem since this book was published when I was seven years old or so, but I thought I’d share it with everybody.

The primary predator for the Jurassic Period were various species of Allosaurus. The various subspecies ranged between two and five or so tons:

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While huge compared to contemporary land predators, this is rather small when you consider that the potential prey animals, particularly Apatosaurus, could outweigh even the largest Allosaur by a factor of ten:

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Worse yet, the extreme body length of Apatosaurus posed a particularly thorny problem: It is highly likely that sauropods used their tails for defense, and when 30 tons of muscle swings its tail at you, the injuries could likely be extreme, given the speeds the tail, and the tip in particular, could reach. Robert Bakker believes that sauropod’s tail-tips could exceed the speed of sound, which makes the sauropod tail an incredibly good and lethal defensive tool. Clearly charging a fresh sauropod, especially alone, would be near suicidal for any theropod to attempt. Likewise, lions don’t attack elephants except in cases of extreme hunger, and even then, don’t typically attack adults, which have almost the same size advantage against lions that sauropods enjoyed against allosaurs.

 

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Not featured: living dinosaurs.

Happily, we can look to another modern day predator, a pack hunter that can and does attack animals ten times (and bigger!) successfully.

african_wild_dog

This is the African hunting dog. It ranges between fifty and eighty pounds, which is fairly small for what is a big-game predator-they will attack anything up to Cape Buffalo in size, which is an insane size difference-adult buffalo can weigh 1500 pounds, nearly twenty times as large as even the largest African hunting dog. Obviously, a single dog would get destroyed directly attacking an adult buffalo, which are noted for aggressiveness towards predators and have the size and armament to match.

But, African hunting dogs are smarter than that. They are communal animals that live in packs of six to twenty individuals, and the basis of their approach to large game, I think, is perfect for our tiny, hungry allosaurs trying to eat gigantic sauropods:

They run them until they’re exhausted. Hunting dogs are excellent long-distance runners, able to maintain speeds of 35mph for miles. Even notably aggressive herbivores, such as cape buffalo, will run from predators if it’s available as an option, and hunting dogs exploit this to an extreme by simply having much better cardiovascular endurance than their prey.

Allosaurs, too, were probably good runners. They had similar cardiovascular systems to modern-day birds, including air sacs branching from the lungs to allow a much higher exercise rate, and it’s not an unreasonable assumption that such relatively small predators worked in packs, both to defend prey from other theropods and to make the probability of a kill much higher (our hunting dogs have remarkably high success rates compared to other African land predators). This strikes me as the only reasonable way Allosaurs could ever have feasibly hunted gigantic sauropods-by spooking them into a fairly slow, but ultimately exhausting, stampede, and then picking off a straggler that was simply too tired to fight anymore. Hunting dogs will also cripple prey instead of killing it outright, and it’s fairly reasonable that Allosaurus could have done this too-Allosaur teeth are “blades” to Tyrannosaur “spikes”, well suited for slashing and creating superficial wounds that become serious over time.

In my mind’s eye, this is an incredible scene: enormous, bird-like predators running even more gigantic prey to exhaustion before closing in for a final kill. The Age Of Reptiles was one terrifying place, but it’s also quite cool. 🙂

Dinosaur size figures courtesy of wolfram-alpha; hunting dog image courtesy http://blueplanetbiomes.org

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