community
june6
2019
Beavers are Eager to Help Restore Watersheds continued from front page
Beavers are considered a key- ence coho salmon recovery in Oregon’s confining hillslopes that will easily cre-
stone species – a plant or animal that Coast Range.
ate a floodplain and develop into a pond
plays a critical role in how an ecosystem
The BDAs Trask and his crew behind the dam.
functions – a species which would dras- constructed in the Tillamook Forest in-
Because this is a pilot project,
tically change that ecosystem if it were volved pounding in a row of vertical, the hope is to answer several questions:
removed. Beavers tend to live
• Will beavers naturally colo-
where they have good access
nize an area if a BDA is in-
to their preferred foods, which
stalled?
include the bark and twigs of
• How effective will different
willows, alder, and other de-
BDA designs be?
ciduous trees, as well as ferns,
• Will human installed BDAs
grasses, blackberries, aquatic
provide winter habitat for
plants, and agricultural crops,
salmon even if beaver don’t
but they’re also pretty adapt-
colonize a BDA site?
able. They live along rivers
• Does the installation of
and small streams, in ponds,
BDAs improve the survival
marshes, and lakes, and even
rate of salmon?
ditches that have a year-round
Trask led us to several
water flow. If they don’t have
BDAs on one creek, took us
deep enough water avail-
to see a large natural beaver
able, beavers will build dams
dam at another location for
across a water flow to create
comparison, and then took us
their own water impound-
to see several more installa-
ment, using nearby trees.
tions on a different stream.
Beavers build lodges
The results of this BDA
in their ponds – mounds of
project are mixed, but after
branches and logs plastered
just nine months and one win-
with mud that have underwa-
ter, it’s still too early to tell
ter entrances. They also dig
just how effective they will
dens into stream banks, and
be.
under logs or stumps.
Beaver Believers!
Beavers breed be-
Interest in beavers and
tween January and March
their impacts on ecosystems
and litters of between one and
BDAs are constructed by pounding in a row of vertical Douglas has been growing during the
eight kits are born between
fir posts across a stream, which are then interwoven with
last several decades, and has
April and June. Kits gener-
vine maple or Doug fir limbs. Ideally the BDA will provide
really accelerated in the last
a prime location for beavers to naturally colonize.
ally live with the adults for
several years, particularly in
two years and then head off to
the Pacific Northwest. The
mate and start their own colonies. Colo- nine-foot lengths of Douglas fir, rang- search for more ways to effectively re-
nies usually contain one breeding pair of ing in diameter from five to 12 inches, store salmon habitat has been one of the
adults and recently born kits.
across a stream. The posts are then in- main reasons, as fish counts of returning
At an average size of 40 pounds, terwoven with vine maple or Doug fir salmonids continue to fluctuate. Water-
beavers in Oregon only have a few pred- limbs. Ideally the BDA will catch more
ators, including bears, coyotes, and cou- debris flowing downstream, retain more
gars. They generally live for five to 10 water, and will provide a prime location
years in the wild.
for beavers to naturally colonize, and
The benefits of beaver dams on maintain the dam the humans started for
streams can be profound. Their dams them.
slow the flow of water in streams, and
At many of the installation sites,
cool it down in the process, creating Trask left food caches, constructed cover
enhanced habitat for fish and drinking and denning opportunities, and removed
water for other species, especially in dry trees to provide sunlight to willow plant-
summer months. During heavier winter ings, in order to encourage beaver colo-
flows, beaver ponds provide shelter for nization.
both adult and juvenile fish. They help
Trask explained that prior to
control flood conditions during severe the installation of the BDAs, an assess-
rainfalls. They also recharge ground wa- ment was made of stream reaches in
ter supplies.
the region, looking for potential sites.
In August 2018 Trask Consult- Those identified sites were then “ground
ing was hired by the UNWC to work on truthed” to show evidence of a historical
a pilot project to install 27 BDAs on four beaver population in the area. Other cri-
different streams in an attempt to en- teria that make good BDA sites include a
courage beaver repopulation and influ- series of low terraced stream profiles and
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shed councils and conservation groups
have focused efforts on improving fish
passage in streams by replacing impass-
able culverts, but those projects are of-
ten very expensive. Recently they’ve
been enhancing fish habitat through the
placement of large woody debris back
into streams, after years of humans pur-
posely clearing waterways. The large
logs slow the stream flow, create pools
and hiding spots for fish, and most im-
portantly, capture mobile gravels that lift
the stream channel back up to its historic
flood plain.
There seems to be little ques-
tion that beavers, and their dams and
ponds, have historically been beneficial
for salmon. They obviously have suc-
cessfully survived together in the same
streams for centuries – a recent bumper-
sticker may have said it best – “Beaver
taught salmon to jump.”
That being said, some wildlife
biologists and fish passage experts have
retained a healthy skepticism about re-
introducing beavers into known salmon
bearing streams.
Greg Apke is the state-wide
Fish Passage Program Coordinator for
ODFW who took part in our BDA tour
led by Trask. “In my role I get to see
projects across the whole state,” said
Apke at the start of the tour. “Beaver
Dam Analogues have become the new
restoration tool, not just here in the Ne-
halem basin, but particularly on the east
side of the state. We’re seeing hundreds
of these being applied. I have a lot of
faith in Steve and he has a perspective
I don’t have, so when Steve talks, I try
to listen. I’m not an opponent, because I
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