12:12pm

Fri April 20, 2012
Krulwich Wonders...

Monster-Sized Rabbits Discovered; Sadly, They Can't Hop

Originally published on Thu April 26, 2012 9:41 am

What if, one day, an ordinary cockroach scuttling across my kitchen floor gets hit by gamma rays from deep space that trigger a gene that triggers more genes, so that suddenly, my little cockroach is a thousand times bigger, and a thousand times hungrier. So when it turns up, 100 feet tall, knocking down trees, salivating and gazing hungrily at Coach Pelligrew's lacrosse team at Riverdelle High, not only do the girls all start screaming, not only are helicopters summoned, not only does the president reach for the Just In Case Red Button — the one reserved for enormous cockroaches — not only .... What? What do you mean, this can't happen?

Dang. Creatures, when they get bigger, change shape. They don't just swell up. Limbs, necks, torsos change. They stretch, shrink, fatten; they look different. Monster cockroaches wouldn't resemble little cockroaches. I know this because of Brian Switek's recent story about monster bunny rabbits.

I'm not talking here about big movie rabbits, like Jimmy Stewart's friend Harvey. No, I'm talking real rabbits. This is a tale of science. It's true. Even a recent discovery. Paleontologists Josep Quintana, Meike Kohler and Salvador Moya-Sola were digging on the island of Minorca, off Spain, and they found fossil evidence of enormous rabbits in a wedge of red sandstone.

Called Nuralagus rex ("King of the Rabbits"), these animals migrated from Europe, but 3 million to 5 million years ago on Minorca, they faced no competition from predators, had lots of food, and so, over time, they grew to weigh, on average, 26 pounds. That's six times bigger than ordinary, wild modern rabbits.

Quintana and colleagues were able to recover an almost complete skeleton from the surrounding rock, so we now know what a very enlarged wild rabbit would look like, and the changes are, well, surprising.

Think of a modern rabbit. What do they do? They hop, they scamper, they have ridiculously big ears.

Here's what Quintana, Kohler and Mova-Sola discovered about their Minorcan giant:

It didn't hop much. (Or so it seems.) When you compare them, the bigger rabbit's lower spine is relatively stiff — and that, say the scientists, "reduced leaping capabilities."

Plus, notice the feet. As the drawings show, a modern rabbit (in the foreground) has padded fore- and hind feet that soften the shock of a landing. Not so the ancient giant. It's feet lack pads, and, says Brian Switek, "the rabbit's whole forefoot would have contacted the ground, rather than just the tips of the toes as in other rabbits," making big leaps more dangerous. So what we have, then, is perhaps a nonleaping (or warily leaping) rabbit. But that's not all.

Check out the ears.

Modern rabbits have huge ears. They have to, to be alert. They are being hunted by foxes, wolves, owls, coyotes. But that was not a problem 3 million years ago on Minorca, says Brian.

"For a giant rabbit, Nuralagus had a relatively small head with small eyes, and the ear holes on the outside of the skull are no larger than they are in European rabbits. Small brain, small eyes, small ears and a husky body — this was not a rabbit that was well-suited to quickly detecting and escaping danger."

So getting Hollywoodish for a moment, Brian says his favorite big rabbit movie is a 1972 horror flick Night of the Lepus, about an Arizona town invaded by giant rabbits. They did it the old-fashioned way, taking a bunch of real rabbits, surrounding them with teeny props, itsy-bitsy houses, miniaturized cacti, trees (and the occasional actor in a rabbit costume) to create the monster effect. But for all these changes, they still look exactly like bunny rabbits, only bigger. The film was a huge flop, because no matter how much the actors screamed, no matter how much blood was thrown about, nobody got scared. There is something about a bunny that wants to be cuddled.

Had the filmmakers consulted a scientist, they could have — with total propriety — given those rabbits scarier bodies. Because, as we've said, bigger critters can and do change form. If, however, the scientists had been our three Minorcan paleontologists, their horror film would have featured big rabbits that are slow to leap, fearful of landing on sharp pebbles and hard of hearing. I'm not sure that's a scarier movie ... unless they find an audience that's frightened by loss of balance and broken limbs. Give me and my friends another decade or so, and this idea could be an incredible nail-biter.


I found Brian Switek's meditations on rabbit fossils on his blog, called "Laelaps." The underlying science paper can be found here. It was published in the Journal of Vertebrate Paleontology.

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