58 Nebraskaland • August-September 2019
MIXED BAG
Anyone who has watched a North
American beaver (Castor canadensis)
gnaw through a tree trunk has surely
been in awe of its proficiency. Using
teeth to whittle on wood, after all, is
a task neither appealing to humans
nor something the American Dental
Association advises us to do.
Those four orange incisors that
protrude as much as one inch from the
top and bottom of a beaver's mouth
comprise just one remarkable feature
of North America's largest rodent,
and perhaps its most important tool.
They allow the beavers to not only cut
timber for building lodges and dams,
but also allow them to eat some of
their favorite foods – tree bark and the
thin layer of growing tissue beneath it,
known as cambium.
Remarkably, the beaver's incisors
continue to grow throughout their life
span, which is typically 10-15 years. In
fact, the beaver's front teeth can grow
as much as four feet per year – a figure
greater than its body length.
If a beaver would not chew, his teeth
would surely become too long to be
useful. The incisors are designed to
abrade and are self-sharpening. With
strong enamel in front and softer
dentin in the back, they are honed to
a sharp edge with each bite. A set of
16 molars distributed evenly toward
the rear of their mouths complete the
chewing process.
One would think the incisors might
be pearly white, considering that
they are constantly being replaced by
new material. However, the orange
coloration of the front teeth is not
directly from food stains, but rather
is indicative of enamel rich with
iron – the same mineral that makes
blood red. That iron, as opposed to
the magnesium found in the enamel
of most animal teeth, makes beaver
teeth especially strong, hinders decay
by resisting acid and bolsters strength.
The beaver is certainly worthy
of awe, not only for its increasingly
appreciated value to wetlands but also
for its four orange tools.
THOSE TOOL-SHARPENING DAM BUILDERS
By Justin Haag
A close-up of a beaver's orange
incisors.
A camera trap image shows a beaver swimming near a felled tree on Little Bordeaux Creek near Chadron.
PHOTOS
BY
JUSTIN
HAAG
