Terrier-boy transformed into a velociraptor before my very eyes!
We were walking along, minding our own business, when a momentary ruffling of leaves on the side of the pavement captured Dash’s attention and instinct took over…
head periscopes right…
ears swivel forward, nostrils flare…
field of vision narrows, eyes become lasers…
muscles tense into compressed springs…
in the pause between two heartbeats the chase is on!
AND…ended just as quickly by that damned ever-present leash. Grrrr.
Initially, I assumed Dash’s prey response had been triggered by a mouse or vole, maybe a chipmunk. Holding him back by the harness, I leaned in for a closer look without really expecting to see anything but fern and wood violet leaves; small rodents usually dive for cover when a predator is on patrol. They don’t risk a backward glance.
So I was surprised and delighted to see small, dark-bright eyes staring back at me from beneath an impromptu stone roof. Not a rodent after all, but an insectivore. A northern short-tailed shrew (Blarina brevicauda) standing his ground against monsters (Dash and me) larger, in relative size, than a T-rex. Fearless!
Or maybe just hungry.
Thanks to an extremely high metabolic rate, the northern short-tailed shrew (let’s go with NSTS for the sake of brevity) has to eat every 2-3 hours to avoid starvation. That makes for a mighty motivated and efficient predator. I’ll bet you if an NSTS was invited to a screening of Jurassic Park, and saw how much time the velociraptors waste stalking kids in the kitchen, he’d be thinking, “Sheesh… amateurs!” Or maybe he doesn’t need to see the movie. According to the fossil record, shrew-like mammals arrived in time to observe real dinosaurs stomping around on planet Earth. Not this particular shrew of course, but it could be buried deep in his genetic memory.
Finding, catching, and eating earthworms, snails and slugs, spiders, insects, frogs and salamanders, mice and voles, along with some seeds and fungi, is a shrew’s full-time 24/7/365 job. Sometimes they even eat each other. All those meals add up to a daily grocery tab of three times the NSTS’s weight. Think of it this way: if Dash were a shrew, he’d need to eat nearly 65 lbs of food every 24 hours, and if I were a shrew I’d need to eat… well, it’s none of your business how much I’d need to eat.
This voracious consumer tips the scales, barely, at 15-30g (0.53-1.06 oz) but he and his kind are literally red in tooth (and only figuratively of claw). Unlike rodents, a shrew’s teeth do not grow continuously. One set of choppers has to last for their entire life, but red-toothed shrews (Soricinae) have helpful iron deposits that provide additional strength to the surfaces most subjected to wear and tear.
Insectivores are one of only three known living mammal Orders with member species that produce venom. The saliva of a NSTS can paralyze or kill prey, even some animals larger than itself. Nothing as large as a human or a dog, mind you, although the pain of a bite can last several days.
Toxic spit certainly comes in handy when it’s time to appease that insatiable hunger. But before you can bite your dinner, to immobilize or eat it, you have to find it. Often in low- or no-light conditions. Lucky for the NSTS, there’s this thing called echolocation. You would think, given how many terrestrial mammals live at least a partially subterranean life, echolocating would be a pretty common talent. You would be wrong. Only rats, the tenrecs of Madagascar, the solenodons, and three species of shrews, including the NSTS, are known to have this ability. Unlike bats (which, because they can fly, are not technically classified as terrestrial mammals), shrews use low-amplitude, multi-harmonic sounds rather than clicks. It appears these calls are used primarily to collect information about their habitat rather than to zero-in on a food source. Still, you can’t find your way to prey if you can’t find your way.
Even with venom and ultrasonic squeaks, life isn’t a picnic. NSTSs (and shrews in general) have a high mortality rate. Winter is particularly brutal, especially if the shrew in question doesn’t have enough cached food to carry it through the lean times, when mercury itself remains huddled in a bulb-burrow. Summer brings its own set of challenges; temperatures above 95°F (35°C) are deadly for shrews, causing the animals to shift their periods of above-ground activity, interfering with their ability to find their 8-12 square meals per day.
It goes without saying (but here I am saying it anyway) that even fierce predators are often prey as well. Shrews are no exception. Despite spending much of their lives hidden in subsurface tunnels, under leaves, leaf litter, and snow, NSTS become a meal, or part of a meal, for many species of fish, reptiles, birds, and mammals.
It’s a predator-eat-predator world out there and size isn’t everything. You’ve got to stay hungry. As the saying goes, it’s not the size of the dog in the fight that counts, it’s the size of the fight in the dog. Or the shrew. They’re still around, still hungry, and the only dinosaurs to be found are computer generated and animatronic.
I guess that settles any argument over who ruled on Isla Nublar, and who got voted off the island.
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© 2017 Next-Door Nature. Reprints welcomed with written permission from the author. Thanks to the following photographers for making their work available through the Creative Commons license: Gilles Gonthier, Goran tek-en, and snapp3r.