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As a child I
was fortunate enough to spend many of my summers at a guest
ranch high in the San Juan Mountains. Near the ranch was a chain
of twenty-eight beaver ponds, one of which was quite large. The
pond was a major attraction for photographers looking for a
beautiful reflection shot, families watching the beavers work in
the evening, and of course, fishermen. From horseback on a ridge
above the biggest beaver pond, riders could occasionally see a
dark torpedo shape cruising near the shoreline. Rainbow trout in
the five to seven pound range thrived here! While I could catch
plenty of trout from the streams, small ponds, and reservoirs in
the area, try as I may, I could never catch one of the lunkers
in what was simply known as the Big Beaver Pond. I couldn't
consider myself an accomplished angler until I caught one of its
nice rainbows. The "big one" eluded me throughout my teenage
years, however, and then came college and a career. A number of
years had past before I found myself standing at the old
shoreline of the beaver pond, fly rod in hand.
The pond was all but gone. The beavers had long since
disappeared and the dam had given in to the erosive force of the
water. A stream narrow enough to straddle wound through the
green grass growing in soil that had once been several feet
under water. A small pool still existed near the dam and a few
small brookies were rising for their evening meal. It was on the
second cast to this pool that the rainbow hit. I could see right
away that this was the biggest rainbow I had ever hooked. After
a short fight (there was really nowhere else for him to go) I
gently eased him from the water. But when I lifted up the
rainbow the experience was bittersweet. A twenty-two and a half
inch rainbow ought to weigh five pounds. This fish was barely
two. As the beaver pond subsided over the years, the food supply
had dwindled, and this once-trophy fish had been starving to
death. Unable to find enough food energy to support a fish her
size, she had been slowly consuming her own body to stay alive.
In college I'm sure I studied beavers and beaver pond ecology. I
probably could have recalled any number of facts about Castor
canadensis and listed various ways beavers impact the
environment. But it wasn't until I caught that rainbow that I
really understood what I already knew. Beavers had changed a
small part of the world and as a result (one of many), fish grew
large. The beavers left the area and as a result (one of many),
large fish began to die. There is no other animal, besides man
of course, that alters the environment to the degree that
beavers do and, consequently, affects so many other kinds of
living things. More should come to mind when we think of beavers
than sticks and mud. The beaver, then, is certainly worthy of
our attention.
Beaver
Basics
Beavers are rodents. Their closest relatives in our area are
marmots and squirrels. They never stop growing during their
twelve-year average life span. Although a few beavers have
reached weights of over one hundred pounds, weights of forty to
sixty pounds are more typical (prehistoric beavers were much
larger--reaching weights of 700 pounds!). The beaver's incisors
are chisel-shaped and self-sharpening, and capable of cutting
through a six-inch aspen tree in about ten minutes. Beavers are
strictly herbivores, eating bark, small twigs, and aquatic
plants.
Living In A
Wet World
For animals that spend most of their lives in water, beavers are
able to stay remarkably dry. Their fur is coated with a
waterproof oil so moisture never actually reaches the skin. The
inside of their ears and nostrils can be closed to form a
watertight seal when diving. Skin folds behind their incisors
allowing them to cut and hold branches below the surface without
taking in water. Webbed hind feet and powerful rear legs provide
speed when swimming. A clear, third eyelid protects the eyes
while letting the beaver see under water. Beavers are certainly
well-adapted for their aquatic environment!
A Beaver's
Tail
The surest way to identify an animal as a beaver is by the tail.
The wide, flat, paddle-shaped tail serves several important
purposes. It is a very effective rudder, particularly when the
beaver swims with a heavy log being drug on one side. As a
diving plane, the tail allows the beaver to quickly change depth
underwater. The tail also acts as a prop to support the beaver
when feeding or cutting trees. When it perceives danger, the
beaver will slap the water's surface with its tail sending a
warning that can be heard half a mile away.
Why Build A
Dam?
Although beavers are well-adapted for an aquatic environment,
their preferred foods are found on dry land. With the exception
of river otters, which will sometimes prey on young beavers,
beavers do not need to worry about predators when in the water.
On dry land, though, they are easy prey for experienced
predators such as mountain lions, coyotes, and bears. When a
beaver builds a dam, the raised water level gives the beaver
access to the newly flooded food sources and decreases the
distance from trees to the safety of water. The depths of the
pond provide a safe and convenient cache for storing a winter's
supply of edible branches. Beavers seldom stop with just one
pond, though. A chain of ponds is often created to give beavers
safe access to an even larger food supply.
A Room At
The Lodge
The beaver
lodge, built of cut logs, branches, and mud, provides a safe
year-round home for beavers. All entrances to the lodge (there
are several) are under water. The living space of the lodge is
above water, however, and a bedding of soft, thin wood fibers
provides warmth and comfort. During the winter, the beaver can
retrieve a stored branch from the bottom of the pond, return to
the lodge, and feed without exposing itself to the world above
the ice.
New
Beginnings
In the
spring, the two-year-olds will be vigorously driven from the
lodge by both adults. These young beavers will usually head
downstream to start their own colonies elsewhere. As the time
for birth approaches, the female will temporarily chase the male
(beavers usually mate for life) and last year's kits out of the
lodge. She will give birth to three or four kits, which will
live with the family for two years.
When Beavers
Go
All beaver
ponds are temporary, limited by the amount of accessible food in
the area. When beavers do abandon a pond, the dam will
deteriorate from lack of maintenance. Stream-born silt will fill
the pond. As the water level drops new plants will begin to
emerge. In time, a careful eye will be needed to find any traces
of the pond in what appears to be a typical mountain meadow with
a small wandering stream.
Many living things are affected by the creation of beaver ponds.
Some animals find their once-dry homes submerged and must seek
shelter elsewhere. Other animals – ducks for example – are
attracted to new beaver ponds. Deer and elk may find their game
trails disrupted by beaver ponds while moose find a new place to
feed on aquatic plants. Beaver ponds affect people, too.
Photographers can find that perfect reflection shot. Families
can walk to a pond at sundown, spread a blanket on the ground,
and sit and wait for the beavers to come out of their lodge. And
fishermen, if they don't wait too long, just might catch that
trout of a lifetime
©
1997,
2006 Dirk Oden |
