Looking at a hero shrew, you might think hero is a bit of an overstatement, but these tiny mammals have near-super powers. A recent study published in the journal Proceedings of the Royal Society B: Biological Sciences, details the bizarre and amazing spines of hero shrews, which enable them to withstand immense weight.
These small, grayish-brown mammals are related to moles and hedgehogs as part of the order Eulipotyphla, though the shrew’s appearance is more similar to that of a rat. While not the most remarkable mammals on the surface, beneath their fur hero shrews are hiding one of the strangest skeletons in the animal kingdom.
"Hero shrews have crazy-looking spines – their vertebrae are squished flat like a pancake, and they have a bunch of extra places where they touch the vertebrae next to them,” said Stephanie Smith, a postdoctoral researcher at the Field Museum and the University of Chicago and the lead author on the paper in a statement. “It makes a really long stiff column along their back, and there aren't good field reports as to what this structure might be useful for. So, we wanted to look at those vertebrae and figure out how they might be using them."
While hero shrews only weigh a quarter of a pound (about 4 ounces), their interlocking vertebrae mean their spines can withstand an enormous weight compared to the animal’s body size. There are even stories (though potentially apocryphal) of hero shrews surviving being stood on by a full-grown human according to the Mangbetu people of the Congo Basin, where Western scientists first met the hero shrew around 100 years ago.
A 2013 study into these animals found that the hero shrew wasn’t alone, as a second species was discovered. Its spine complexity was somewhere between that of the hero shrew and regular shrews. They hypothesized that the strong backbones enabled the hero shrew to ball up and extend as a way of breaking apart logs to find food, though this behavior has never been observed in the wild. Exactly why these small mammals have such strong spines isn’t clear, but Smith and her team decided to look at CT scans of shrew spines from museum collections to try and understand how they evolved.
"Bones contain a record, to some degree, of the forces that are acting on them during life. There are special cells in the bone that detect when pressure is put on it. They send out signals to reorganize the bone to be better at handling the forces they're under, so you have bones responding throughout an animal's life to habitual forces," Smith explained in a statement. "My absolute favorite example of this was a paper where they put sheep in tall shoes, like high heels, and the different angle of pressure changed the inner structure of their leg bones."
Their results indicated that hero shrew spines are able to withstand immense pressure even when “scrunched up like an inchworm”. This was due to their spines not just being tough on the outside but also dense on the inside, giving a clue to the pressures withstood by the hero shrew’s backbones while it was alive. While it can’t confirm the 2013 study’s hypothesis that hero shrews scrunch up and then extend their spines to tear apart wood in search of food, the finding does indicate such behavior is possible.
To the uninitiated it might seem like a lot of fuss over a shrew, but the researchers highlight that understanding the evolution of these small animals could answer big questions about the evolution of mammals. “Shrews are really interesting ecologically, and they're so small they have almost secret powers,” said Smith. "They're incredibly diverse, and I think they're beautiful. They're dope as hell."