The beaver that lives in trees
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Feb 13, 2017  |  Vote 0    0

The beaver that lives in trees

Arnprior Chronicle-Guide

I think it safe to say that everyone knows that beavers live in water, leaving its safety only to forage on land or to sleep inside a lodge. While they eat both aquatic and terrestrial herbaceous plants, through much of the year, especially in winter, much of their diet consists of the bark and twigs of trees, especially poplar.

Beavers aren’t alone in their fondness for poplar. In the rodent group, there resides another species that also eats bark, twigs, and opening leaves of poplar. Porcupines eat woody material and, like beavers, possess a long intestinal pouch full of bacteria to digest cellulose. Unlike beavers, however, porcupines don’t cut down trees to access meals. They climb trees using their impressive climbing gear: huge claws and rough-skinned feet.

Right now is a good time to see porcupines, for they will sleep in trees during the day (their dark bodies soaking up solar energy), with the lack of leaves making them easy to spot. Other times they sleep in dens situated in rock caverns or hollow trees, venturing out to forage at night. On cold days they conserve energy by lowering their body temperature by 5 degrees C.

Apart from starvation and falling out of trees, Porcupines face another challenge. Some are shot by humans because they damage trees; others die when they cross highways or stop to glean salt from the asphalt. Porcupines are slow moving animals built for climbing, not running, and thus are prone to being hit by cars. They need not run from predators because they own a powerful defence: modified hairs known as quills.

Around 30,000 quills adorn a porcupine’s body, with its lower back and tail particularly well endowed. Contrary to popular belief, porcupines cannot throw quills. An attacker must make contact with them before they get dislodged. When confronted, a porcupine turns its back to an attacker and swings its tail back and forth. Once embedded, overlapping scales allow quills to work their way through flesh when muscles contract and expand. Quills function just like plastic cable zip ties, allowing one-way movement only, which is why they’re so hard to remove from dogs that foolishly attack a porcupine.

Quills have another unusual feature. They have a greasy coating that contains antibiotics. This coating might prevent porcupines from getting infections when they impale themselves with their own weaponry after falling out of a tree, which apparently isn’t rare. It’s also possible that they are meant to hurt, not kill, attackers. Some predators teach their offspring how to hunt; by giving an attacker a memorable lesson, it might pass on its painfully attained knowledge to its young. This wouldn’t apply to fishers, however, for they regularly eat porcupines. They kill them by eventually flipping them over onto their back and attacking their quill-less belly.

Porcupine quills have another unusual feature. Their bases are white and they contain fluorescent compounds — features that make them highly visible at night. Just like the white stripes on a skunk, Porcupine quills provide visual warning.

Perhaps this column’s title might have been: “The Skunk That Lives in Trees!”

The Nature email is mruntz@start.ca

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