The fanged beast

The light from the full moon shines down, glimmering off the soft, brown, velvety fur. It’s rare for this creature to venture above ground. It moves clumsily in search of new food, but pauses. It sensed something. And from the shadows something came at terrifying speed. The creature slashed its giant claws at the predator as it attacked, missing feebly. Despite being more than three times its size, it was no match for the ferocious beast. The creature stepped back clumsily, scraping up dry dirt which hung in the air, glistening in the light of the moon like star dust. Sharp fanged teeth snapped violently at the creature. It’s claws slashed again, but it was no match for the speed for the predator. Retreating awkwardly, the creature felt a sharp pain: the fangs had driven deep inside the muscular arm, so deep they hit bone. The creature limped slowly backwards. The night became darker. The creature flopped down on its stomach. For an animal so used to spending its days living in darkness, it had never seen such pure blackness. The predator inched forward and began its feast.

This was a titanic battle. On a miniature scale. The poor creature whom sunk into darkness was in fact a mole. Our predator, a shrew.

This imaginary clash of the tiny titans sounds fanciful. Yet something like this actually happened. Amongst fossils of humans, hippos, and giant lions, one small bone of a mole humerus was found. The site of Sima del Elfeante, in Spain, has revealed a rich ecosystem long lost, in the very early Pleistocene site in Spain, some 2 million years ago.

For such a rich site in large species, it is amazing that this one bone was looked at. The humerus had bite marks on it, which matched the teeth of the extinct shrew Beremendia fissidens.

The thick mole humerus showing bite marks on the bone. (Image from Bennasar et al 2014)

A shrew biting into the arm of a mole? A bite so hard it went all the way down to the bone? This shrew maybe small, but it was a bad-ass.

Shrews are pretty small animals. All species would comfortably fit in the palm of my hand. There are shrews that are semi-aquatic. Shrews that live underground. Shrews that live in trees. In fact, shrews are one of the most diverse mammal species. Some species even use echolocation to hunt for prey! Their fossils are very abundant in Pleistocene cave sites, thanks to owls. These stealthy hunters feast on shrews and many other small vertebrates. They cannot digest the bones or fur, so they cough them up in balls and spit them out. In caves these can accumulate in their thousands, resulting in hundreds of thousands of tiny bones. These fossils give palaeontologists a rich understanding of past ecosystems.

I spent many months at the Natural History Museum, London, sieving and sorting the tiny bones from ancient owl sick. It might sound tedious, but to see the tiny teeth or vertebrae of little animals hundreds of thousands of years old was addictive. I always got more excited than I should have at seeing a shrew jaw: they are so beautiful and impossibly perfect. One would fit on my fingernail easily. They always made me smile and I would stare at them longer than perhaps I should have. My voyeurism was warranted. The cusps of the back teeth are a vibrant dark red colour. This is amazing: shrews add iron particles to their back teeth to make them stronger and more resistant to wear. So the little critters can enjoy crunching on the tough exoskeletons of beetles and grasshoppers without worrying about cavities.

But flesh eating shrews? With venomous fangs? This may not be as crazy as it sounds. Some shrews do eat dead carcasses if they stumble on them. Some even eat small rodents. The living relative of Beremendia fissidens, the northern-short tailed shrew (Blarina brevicauda), eats fish, amphibians and small mammals.

The gorgeous Northern Short-tailed Shrew, from Canada. (Image Giles Gonthier. Public Domain)

The upper canines of our ancient shrew had a c-shaped groove along the length of the tooth. This is seen in venomous animals, such as snakes, and is used to transport the venom from the venom sac to the animal it bites.  Some researchers don’t think that this ‘channel’ in the tooth signifies venom, but looking at other animals, it seems quite likely. Even more so as it’s living relative the northern short-tailed shrew is venomous. If it was venomous, then it would have been an active predator, not a scavenging animal.

The fangs of our beast, Beremendia fissidens. These fangs injected venom into its prey. (Image from Bennasar et al 2014)

This one small mole bone has given a glimpse into a fraction of time almost two million years ago. What’s more, our shrew must have had a pretty mighty chomp: it left tooth marks on the bone. Tooth marks not from gnawing on a dead carcass, but evidence of an extremely powerful bite.

Knowing there was once a fanged venomous shrew, (and now knowing that there is a venomous shrew alive today!), I for one have a new found respect for shrews. These may be little mammals, but they sure as hell are feisty.

Written by Jan Freedman (@JanFreedman)

Further reading:

Bennasar, M., et al. (2015). ‘Exceptional biting capacities of the Early Pleistocene fossil shrew Beremendia fissidens (Soricidae, Eulipotyphla, Mammalia): new taphonomic evidence.’ Historical Biology. 27(8). pp.978-986. [Full article]

Martin, I. G. (1981) ‘Venom of the short-tailed shrew (Blarina brevicauda) as an insect immobilising agent.’ Journal of Mammology. 62. pp.189-192. [Abstract only]

Masaki, M., et al. (2004) ‘Blarina toxin, a mammalian lethal venom from the short-tailed shrew Blarina brevicauda: isolation and charachterization.’PNAS. 101 (20). pp. 7542-7547. [Full article]

Tomasi, T. E. (1979) ‘Ecolocation by the short-tailed shrew Blarina brevicauda.’ Journal of Mammology. 60(4). Pp.751-759. [Abstract only]

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6 Responses to The fanged beast

  1. tabbyrenelle says:

    Gosh so why did shakespeare compare the woman to a shrew???
    ultimately i like your SCIENCE post but i gotta wonder.

  2. After reading this article, I’ve developed a new admiration for shrews both living and extinct. They are quite remarkable animals. The fossil teeth you wrote about reminds me a bit of Uatchitodon, a venomous Jurassic reptile from the Eastern United States known only from a few teeth with what appear to be venom ducts.

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