By Jake Buehler
At first glance, hero shrews don’t appear to live up to their name. But these fuzzy, molelike animals are the Clark Kents of the shrew world, with superpowers hidden beneath their humble exteriors. Their backbones are like nothing else in the animal kingdom: the vertebrae interlock, making the spine extremely strong and rigid when compressed.
Now a 3-D analysis of the bone structure reveals that the vertebrae are exceptionally dense, with neatly reinforcing struts that lend toughness too. That structure may provide insight into how these unique backbones may benefit the animals in nature, researchers report April 28 in Proceedings of the Royal Society B.
Two hero shrew species (Scutisorex) can be found in the palm forests of the Democratic Republic of the Congo. Their strength astonished American and European explorers in the 1910s, when Congo’s local Mangbetu people reportedly demonstrated that an adult man could step on the animal — only the heft of a deck of cards — without causing any harm.
“That story may or may not be apocryphal,” says Stephanie Smith, a vertebrate functional morphologist at the Field Museum of Natural History in Chicago. That particular demonstration “certainly has not been reproduced.”
The shrew’s backbone is flat on top and underneath, featuring broad side flanges with lots of fingerlike projections. To probe its strength, Smith and museum colleague Kenneth Angielczyk used a 3-D X-ray technique to scan the internal structure of vertebrae from 20 skeletal museum specimens. The skeletons were from both hero shrews and the goliath shrew (Crocidura goliath), which is similar in size to the hero shrew, but with a more standard backbone. The researchers hoped that studying the density and orientation of holes and struts in the spongey interior of the bones would reveal the magnitude and direction of forces the animals might have experienced during their lives.
Compared with goliath shrews, hero shrews had more, and wider, vertebrae. Internally, the hero shrews’ vertebrae also featured many reinforcing rodlike structures that made the spongey bone very dense. These struts were mostly oriented in the head-to-tail direction, while the goliath shrews’ struts were less aligned with any given direction, the team reports.