Colours of Wildlife: Hero Shrew
Created | Updated Jun 28, 2015
Hero Shrew
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Some time ago I told you about the Hero Rats; now let me tell you about another kind of heroic critter! Thia is a Hero Shrew, Scutisorex somereni. It is sometimes also called an Armoured Shrew. We'll get to the reason for its name in just a minute. But first …
The Story of the Shrews
Shrews are perhaps one of the most underrated mammalian groups. Most of them are tiny and rarely seen. They resemble mice, but are something completely different. They are classified in the order Insectivora, which used to include a large number of insectivorous mammalian groups but which have been recently understood to not all be closely related to each other, with the result that several distinct groups have been split off from the old Insectivora. But shrews are still in it, as are moles. Shrews are mammals that can be called 'primitive' since they still resemble in most ways the very first mammals that came into existence about 200 million years ago. That was even before the dinosaurs came into their legacy of world domination which would last up to about 65 million years ago. For most of the reign of the dinosaurs, most mammals remained small and shrew-like – although there were several exceptions; a few mammals grew large enough even to catch and feed on small dinosaurs!
Shrews, like the first mammals, have small bodies with a conservative build: five clawed toes on the front and back feet, a well-developed tail, small eyes, pointed snouts adorned with sensitive whiskers, dense, soft fur, relatively unspecialized teeth. Most shrews look very similar. They are greyish, brownish or blackish in colour, with no conspicuous adornments.
But just because shrews appear primitive, doesn't mean they have not evolved. They are as modern as any other existing group of animals. Their smallness hides many very interesting features. For instance, they are one of only a very few mammalian families that have developed venom. Some shrews have salivary glands secreting a venomous substance that is powerful enough to kill animals as large as themselves. Another interesting feature is that some shrews might use echolocation … their squeaks are so high that they're inaudible to humans, but like bats, the shrews use the echoes of these ultrasonic sounds to locate their prey. All shrews have extremely fast metabolisms, and have to eat constantly – sometimes as much as their own bodyweight each day. They die if they don't eat for several hours. Their hearts beat more than ten times a second … they breathe in and out at a similar rate. Even in cold regions, shrews stay constantly active. They don't sleep during the night as other animals, instead apparently functioning in several daily active-and-resting cycles, these typically lasting three hours or so. Shrews are predacious, hunting invertebrates as well as vertebrates up to, or sometimes exceeding, their own size. They include some of the smallest mammals in the world. They're found in Europe, Asia, Africa and North America.
Heroes among the Shrews
So I hope you understand that shrews are actually rather amazing little critters. And among them the hero shrew stands out! Not so much for its behaviour as for a unique physical gift. This was first demonstrated for Europeans when the naturalists Herbert Lang and James Chapin met up with the Mangbetu tribe of the Congo. The westerners were astounded when these tribesmen produced a small shrew and put it on the ground. Not so much that, but what happened next: one of the men, weighing about 72 kg/160 lbs, stepped on the little shrew. He trod on it with his entire weight, balancing on one foot on top of the shrew, it is said for a few minutes. He then took his foot off. The little shrew shrugged it off and scurried away as if it was nothing!
The hero shrews, it turns out, have absolutely unique backbones. These are much thicker than those of any other shrew. Also, the vertebrae are locked together by a kind of basketwork of lengthened struts growing from their outer margins. All in all this makes the spine of the hero shrew proportionately the strongest in the animal kingdom! When stepped on, the strength as well as the curvature of the spine helps to protect the shrew's inner organs.
Because of this, the local people revere these shrews. They are considered talismans what will protect warriors in battle – even the ashes of a burnt shrew are considered to impart invincibility. Medicine made from the shrews are also believed to give warriors great courage. It is from this esteem that the hero shrew derives its name.
But apart from what people believe about these shrews, and their unique spines, they are much like other shrews. They live in forests, ranging from lowland to mountain forests, in the eastern DRC and Uganda, Rwanda and Burundi. They are fairly large for shrews, reaching 25 cm/10" in total length and a weight of just over 100 g/3.5 ounces. They're greyish in colour. Their spines, in addition to being thicker and stronger, are also proportionately longer than those of other shrews. They usually move around with a hunched back and a trotting rather than a scampering gait. They too actively seek prey all day long: worms, caterpillars, snails, insects, small frogs. Their habitat is moist and life-sustaining year round. They, too, appear to have a venomous saliva, which paralyzes but does not kill their prey. They have scent glands that give them a very pungent smell (especially the males), this probably protecting them against many predators. It tends to stain their sides and chest yellow. It probably also helps the shrews to mark their territories. The smell of one shrew, if strong enough, will repel others.
We don't really know why these shrews have such unique backbones. They seem to be overbuilt for anything they're likely to encounter in the normal course of their lives … getting stepped on by people is certainly not something that happens to them so much that they're evolved especially to counter it! Rather, they may use their strong spines when grubbing around the undergrowth and pushing themselves in underneath rocks and tree stumps or worming into crevices. Their spines are inflexible for side-to-side bending, but can bend upward and downward. The shrews also have very strong muscles for flexing their spines. They also have unusually thick ribs.
A New Hero
We still don't quite know why these shrews have such spines. No other shrew is known with anything approaching the degree of reinforcement that the hero shrew has … at least, none was known until recently. In the early Tweny-First Century, another unusual shrew was found in the Congo. It had a spine that was similar to that of the Hero Shrew, but not quite as massively developed. It had the same pattern of interlocking vertebrae, and consequently is being classified with the Hero Shrew in the genus Scutisorex. It was described in 2013 and named Thor's Hero Shrew. It is remarkable for showing a condition intermediate between the Hero Shrew and other shrews, showing that the armoured spine could have evolved from a more normal kind of backbone.
Not much else is known about hero shrews. They live in a remote and densely forested region. As long as their habitat remains untouched, they are not in danger of extinction.
