This Shrew Can Survive You Standing on It (Maybe. Please Don’t Try)

In 1910, a pair of scientists exploring what is now the Democratic Republic of Congo came across a shrew of improbable furriness and size (though it still weighed in at just a tenth of a pound). Locals identified it as the hero shrew, whose bones, pelt, and even ashes granted invincibility when carried into battle.

To prove the shrew’s powers, a grown man grabbed one, placed it on the ground, and stood on it for several minutes — a performance I’ve unremorsefully decided to dub The Maiming of the Shrew. When the man stepped off, the creature hesitated briefly with “a few shivering movements” before scurrying away, “none the worse for this mad experience and apparently in no need of the wild applause and exhortations” of the gathered crowd.

Yeah, spines aren’t supposed to look like this. Unless you’re a hero shrew. Then it’s normal.

This account, which appeared in the Bulletin of the American Museum of Natural History, raises a few questions, foremost of course being, what kind of scoundrel would be the first to see if he could stand on this animal for several minutes without killing it? And how many different critters did he try this on before finding success with the hero shrew? A perhaps more important and more answerable question might be, how on Earth could a 6-inch-long creature survive such trauma?

Also known as the armored shrew, the hero shrew derives its powers from an absolutely incredible backbone, which is so wildly different from any other vertebrate’s that it looks like the prankish creation of some bored scientist, à la the fantastical “specimens” of the jackalope or the Fiji mermaid. And while no respectable researcher would recreate the aforementioned test of the backbone’s strength, we can say with confidence that this is the animal kingdom’s most remarkable spine.

Feel the back of your neck. Notice the bump at the base? It’s called a process, and it’s the part of your vertebrae that muscles and ligaments attach to. Most vertebrates, including us, have that single process at the top of each vertebra and a few others on either side.

But the hero shrew has an astounding 10 to 20 processes per vertebra, according to William Stanley, collection manager of mammals at Chicago’s Field Museum, “and they interlock with the processes to the front and to the back of each vertebra so that you have this very ornate, intricately digitated series of backbones that give these animals incredible strength.”

According to Stanley, its spine is, relative to body size, four times more robust than that of any other vertebrate, which poses quite the evolutionary conundrum: This is a singular species whose backbone is miles away from its shrew cousins. There’s a more typical shrew at one extreme and then the hero shrew at the other, with no species in between. This might suggest that the evolution of the robust spine was supremely rapid and dramatic, an evolutionary principle known as punctuated equilibrium, because there are no intermediate forms between the two to indicate a more gradual development.

But then Stanley traveled to the Congo in 2012 to study disease transmission in rodents and found his own shrew. It wasn’t until he brought the specimen back to the Field Museum and analyzed its DNA that he discovered that it was in fact a hero shrew — only a bit different. A dissection revealed a somewhat less robust spine, and it became clear that Stanley may have discovered an intermediate species.

Shrew spines from left to right: Scutisorex somereni (original hero shrew), Scutisorex thori (Thor’s hero shrew), and Crocidura olivieri (a more “normal” African giant shrew). Please note that those numbers do not appear naturally on shrew skeletons. They were added by a human with a permanent pen.

The new form has seven or eight vertebrae in its lumbar region to the original hero shrew’s 10 or 11 (and our five), with about half the processes sticking out of the sides of each. And while they also interlock, they’re a bit broader. Stanley named it Thor’s hero shrew after the man who inspired his work in mammalogy, Cal State Humboldt’s Thor Holmes, who just so happens to share his name and magnificent beard with the Norse god of strength.

“This new species exhibits features that could be intermediate,” said Stanley. “That’s not to say that they are. One possibility is that there was a punctuated equilibrium event where there was the standard shrew backbone and then suddenly the first discovered hero shrew evolved out of that. And this form that we just found subsequently evolved from that.”

So now we know of at least two species of hero shrews with freakishly robust spines, but then we inevitably come to the why. Why evolve such an impressive backbone? (After all, it “certainly wouldn’t serve to just carry people around,” said Stanley.)

After discovering Thor’s hero shrew, Stanley recalled a conversation he’d had 15 years earlier with a colleague, Lynn Robbins, who had not only come in contact with the original hero shrew during his time in Africa, but had formulated a theory for the purpose of its spine.

Robbins had watched locals yank dead palm leaves off trees in search of hidden beetle grubs, and it was in these palm forests where hero shrews seemed to proliferate. He theorized that the shrews hunt the same grubs in much the same manner, squeezing themselves between the leaves and the trunk of the tree and literally putting their backs into it to leverage the fronds and get at the quarry.

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