Anchorage David Saalfeld Regional Wildlife Biologist Alaska - - PowerPoint PPT Presentation

Beaver Management in Anchorage

David Saalfeld Regional Wildlife Biologist Alaska Department of Fish and Game

General Biology

• Largest rodent in North America
• Continue to grow in body size throughout

their lives

• Average 40-70 lbs, but have been known to

grow to 100 lbs

• Primarily nocturnal, but sometimes active

during day

North American Range

Reproduction

• Monogamous—mated pair will live together for

many years, sometimes for life

• Breeding season in January/February
• Gestation 107-110 days
• 2-4 kits born April-June
• Kits eyes are open at

birth, and they are covered with soft fur

• Nurse for 2-3 months
• Can swim at 4 days

Longevity

• When foraging away from

water, vulnerable to wolves, coyotes, bears, lynx

• Other causes of mortality

include winter starvation, disease…and falling trees

• Generally live 5-10 years in

wild

Colonies

• Beavers live in family units: Mom, Dad, and

the kits

• Kits stay with parents until 2 years old
• Most beavers will reproduce at 3 years of age
• Beavers are very territorial, and will defend

their area from any other beavers

Designed for Underwater Operations

• Nictitating membranes protect eyes
• Nose and ear valves close
• Draws lips tightly behind teeth when carrying

wood

• Can hold breath for 10-15 minutes

Coat

• Short, fine hairs for warmth
• Longer hairs for waterproofing
• Beavers frequently groom their fur and waterproof

it with castor

Castoreum

• Found in “glands” near the base of the tail
• Both male and females have castor sacs
• Used for marking territory
• Protect and waterproof fur
• Human uses for castor include lure for

trapping beavers, perfume, food additive, and historically it was used in some medicines

Tail

• Used as a rudder
• Slaps as a warning
• Used for balance when standing on hind legs

Feet

• Webbed hind feet for swimming
• Front paws skillful at manipulating objects

Teeth

• Never stop growing
• Self-sharpening—the inner surface is softer

than the outer enamel, so wears away faster to create a sharp edge

Diet

• Vegetarians
• Fresh leaves, stems, twigs, bark, aquatic plants, roots, grasses
• Preferred tree species include alder, aspen, birch, cottonwood,

poplar and willow

• If preferred species

unavailable, will eat most woody plants

• Often travel >100 yds

from water

• Food for winter use

stored in underwater caches

Structures

• Dams
• Lodges
• Bank Dens

Dams

• Flood areas for protection from predators, access

to food supply, and to provide underwater entrances to dens.

• Beavers living on water bodies that maintain a

constant level (e.g., lakes, large rivers) do not build dams.

• Dams are constructed and maintained with whatever

materials are available—wood, stones, mud, and plant parts. They vary in size from a small accumulation of woody material to structures 10 ft high and over 165 ft wide

• The average tree used in construction of a dam is 4-

12” at the stump…but use of trees 150’ tall and 5’ across have been recorded

Dams

Lodges and Bank Dens

• The beaver’s home
• Both have one chamber and at least one exit to deep water
• Freestanding lodges usually built in lakes/ponds, or areas

where the bank or water levels aren’t sufficient for a safe bank den

• Bank dens are often in large, swift streams
• Lodges consist of mound of branches and logs, plastered with

mud

• One or more underwater openings lead to tunnels that meet

at the center of the mound

• Bank dens are dug into the banks of streams and large ponds,

and beavers may or may not build a lodge over them

• Bank dens may also be located under stumps, logs, or docks

Lodges

The Challenges of Beaver Management

• Anywhere there are beavers, we two opposing

viewpoints among local residents

• Benefit/Cost

Environmental Benefits

• Water quality
• Creation of habitat for other species
• Creation of open space
• Reduction of erosion

Water Quality

• Beaver ponds help remove sediment and

pollutants from waterways, including suspended solids, total nitrogen, phosphates, carbon, and silicates

Creation of Habitat

• As trees are drowned by rising water, they become

ideal for woodpeckers—whose cavities in turn draw

• ther cavity nesting birds
• Canada Geese and Trumpeter Swans have been

known to depend on beaver lodges for nest sites

Creation of Habitat

• Beaver ponds have been shown to have a

beneficial effect on trout and salmon populations

• Beaver ponds may be especially important

wintering habitat for salmonids

• Beaver dams develop new wetlands, benefitting

a variety of other species, including waterfowl, bears, moose, gulls, etc.

• Removal of some pond-side trees increases the

grass/forb/shrub layer, creating more waterfowl nesting habitat adjacent to water

Creation of Open Space

• When beaver ponds eventually silt in, fertile

“beaver meadows” are gradually formed, creating open space that benefits a variety of

• ther species

Reduction of Erosion

• Beaver dams deepen and reduce flow, decreasing

bank erosion

Beaver/Human Conflicts

• Flooding
• Issues with water facilities such as stormwater

systems

• Damage to forests and landscaping
• Undermine roads
• Dams can sometimes be an impediment to

fish—but not as often as commonly thought

• University Lake—aggressive beavers

“Beaver Fever”

• Debilitating (to humans) gastrointestinal

distress caused by the parasite Giardia lamblia

• You get it from drinking water containing the

parasite

• Beavers are not the only animals that carry it

Anchorage

S Fork Chester Cr University Lake Reflection Lake C a m p b e l l C r e e k L i t t l e C a m p b e l l C r e e k Pond below Alderwood Park Eastchester Lagoon Little Survival Creek Taku Lake

CAMPBELL LAKE SHIP CREEK RABBIT CREEK CRAIG CREEK L I T T L E R A B B I T C R E E K FURROW CREEK FISH CREEK POTTER CREEK O D C R E E K

T u d

• r

Glenn 5th O ' M a l l e y L Seward R a s p b e r r y I n g r a Hillside Elmore International Airport

Management Options

• Education
• Exclusion
• Dam Removal
• Water Flow

Devices

• Trapping/Removal
• Combination

Education

• Speak to community groups
• Educate personnel from other agencies; work

with Municipality to draft policies guiding beaver management in Anchorage

• Educate landowners: often used when there is

not a real problem—beavers are simply present

Exclusion

• Sturdy fencing is the primary

means of exclusion.

• Individual trees are best

wrapped with hardware cloth forming a cylinder standing at least six inches away from the trunk.

• Property is best fenced with

welded wire fencing.

Dam Removal (hand removal)

• Used in certain situations, if volunteers are willing

to put forth effort

Water Flow Devices

(Flooding Prevention)

• Pond Levelers (Beaver Dam Pipes)
• Culvert Protectors
• Combinations

Pond Levelers

• Beavers plug leaks in their dams quickly to

maintain water levels

• The sound of running water stimulates them

to plug holes

• Pond Levelers eliminate the sound and feel of

flowing water

Pond Levelers

Culvert Protectors

• Beavers often plug culvert pipes under roads,

resulting in flooding

• To be effective, a culvert fence needs to be

wide, forcing the beavers to dam a long section of fence

Water Flow Devices

• Appropriate for certain situations, but not all
• Generally most successful if the water level

does not have to be dropped very far

• Must be installed correctly and maintained
• If some degree of elevated water is

acceptable, water flow devices should be considered

• Sometimes trapping is necessary before

installation

Common Reasons for Failure of Water Flow Devices

• Beavers construct a new dam
• Improper design (e.g., insufficient pipe capacity)
• Lack of maintenance
• Beavers dam the fencing
• Vandalism

Relocation

• Very rarely an option
• Most habitat suitable for beavers…already has

beavers

• Beavers are

territorial, so newcomers will likely be chased away

Trapping/Removal

• Last resort—but is often the most practical

solution

• If trapping or shooting is to be done to remove

beavers in the event of conflicts with humans, it is ONLY to be done under a permit issued by ADF&G

• Any beavers removed by lethal means become the

property of the state and hides/skulls are used for educational purposes

• Not a long term solution

Evaluation of a Conflict

• Can beavers and humans coexist in this area?
• Are nonlethal means likely to be successful?
• Is the landowner interested in trying nonlethal

means…at their own expense?

• Is there likely to be damage to a structure or
• ther property?
• What is the landowner willing to do to prevent

future problems?

If you become aware of a conflict between humans and beavers

• Do not take action on your own
• ADF&G needs to evaluate the situation to

decide upon the appropriate management response

• Call ADF&G at 267-2344

Future Issues

• Continue educational efforts to promote

tolerance of beavers where possible

• Evaluate each situation on a case by case basis
• Move toward nonlethal means such as pond

levelers

Questions?