Sumio Harada / American Beaver (Castor canadensis) felled tree, Glacier National Park, Montana

Sumio Harada / American Beaver (Castor canadensis) carrying stick for lodge, Glacier National Park, Montana

Jeff Foott / American Beaver (Castor Canadensis) felled tree, Zion National Park, Utah

Jeff Foott / American Beaver (Castor Canadensis) felled tree, Zion National Park, Utah

Jeff Foott / American Beaver (Castor Canadensis) felled tree, Zion National Park, Utah

Jeff Foott / American Beaver (Castor canadensis) bite marks on tree, Zion National Park, Utah

Michael Quinton / Bald Eagle (Haliaeetus leucocephalus) on American Beaver (Castor canadensis) lodge, Alaska

Michel Roggo / North American beaver (Castor canadensis) swimming in the pool around his lodge, Northern Rockies, British Columbia, Canada, July. Taken for the Freshwater Project.

Hiroya Minakuchi / American Beaver (Castor canadensis) dams on stream, Colorado

David Pattyn / Trees felled by American Beaver (Castor canadensis) Upper Mississippi Wildlife Refuge, on the border of Minnesota and Wisconsin, USA, July.

David Pattyn / Trees felled by American Beaver (Castor canadensis) Upper Mississippi Wildlife Refuge, on the border of Minnesota and Wisconsin, USA, July.

David Pattyn / Trees felled by American Beaver (Castor canadensis) Upper Mississippi Wildlife Refuge, on the border of Minnesota and Wisconsin, USA, July.

Cheryl-Samantha Owen / Canadian Beaver (Castor canadensis) swimming in Fairy Lake, Fairy Glen, near Port Renfrew, Vancouver Island, British Columbia, Canada, July.

Cheryl-Samantha Owen / Canadian Beaver (Castor canadensis) swimming in Fairy Lake, Fairy Glen, near Port Renfrew, Vancouver Island, British Columbia, Canada, July.

Enrique Lopez-Tapia / Fallen tree cut by a North American beaver (Castor canadensis) an invasive species (introduced for fur trade) Tierra del Fuego, Argentina

Enrique Lopez-Tapia / Peatland landscape in Tierra del Fuego with North American beaver (Castor canadensis) dam, an invasive species (introduced for fur trade). Argentina

Enrique Lopez-Tapia / American Beaver (Castor canadensis) dam, an invasive species (introduced for fur trade) in wetlands. Tierra del Fuego National Park.

Ingo Arndt / American Beaver (Castor canadensis) lodge, Yellowsone National Park, Wyoming

Ingo Arndt / American Beaver (Castor canadensis) dam, Yellowstone National Park, Wyoming

Ingo Arndt / American Beaver (Castor canadensis) dam, Yellowstone National Park, Wyoming

Kirkendall-Spring / Beaver cut tree in Maplewood State Park. Minnesota, USA, September

Mary McDonald / American Beaver swimming (Castor canadensis) Denali NP, Alaska, USA

Bryan and Cherry Alexander / Cree woman with Beaver (Castor canadensis) skin stretched out to dry. North Quebec, Canada, 1988.

Bryan and Cherry Alexander / Cree trapper removing Beaver (Castor canadensis)from trap. Quebec, Canada, 1988.

Bryan and Cherry Alexander / Cree woman preparing Beaver (Castor canadensis) for family feast. North Quebec, Canada, 1988.

Pete Oxford / American beaver (Castor canadensis) dam across a stream with a large conical house.Grand Teton National Park, Wyoming. USA

Donald M. Jones / American Beaver (Castor canadensis) carrying cottonwood branches over dam, western Montana

Donald M. Jones / American Beaver (Castor canadensis) eating cottonwood leaf, western Montana

Donald M. Jones / American Beaver (Castor canadensis) carrying branch in water, western Montana

Donald M. Jones / American Beaver (Castor canadensis) tail, western Montana

Donald M. Jones / American Beaver (Castor canadensis) carrying log over dam, western Montana

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) swimming in pond, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) sliding on muddy bank from top of lodge into pond, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) hauling cut branch to pond, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) feeding on bark of cut tree, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) hauling branch to its lodge, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) swimming with cut branch, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) eating willow leaves from cut log, Denali National Park, Alaska

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) swimming with large cut log, Denali National Park, Alaska

George Sanker / American beaver (Castor canadensis) rolling and peeling a small log, Baxter State Park, Maine, USA, November

George Sanker / American beaver (Castor canadensis) swimming carrying food to its lodge, Baxter State Park, Maine, November

George Sanker / American beaver (Castor canadensis) swimming, Walpole, New Hampshire, USA, April

Jerry Monkman / Trees downed by American beavers {Castor canadensis} beside Moores Brook, Ellsworth, Maine, USA. June 2008

Donald M. Jones / American Beaver (Castor canadensis) swimming with willow branch, western Montana

Donald M. Jones / American Beaver (Castor canadensis) on top of lodge, western Montana

Donald M. Jones / American Beaver (Castor canadensis) hauling log over dam, western Montana

Donald M. Jones / American Beaver (Castor canadensis) swimming with branch in mouth, western Montana

Mary McDonald / Two American beavers {Castor canadensis} swimming across lake dragging branch in their mouth, Denali NP, Alaska, USA

Mary McDonald / American beaver {Castor canadensis} swimming across lake dragging branch in its mouth, Denali NP, Alaska, USA

Mary McDonald / American beaver {Castor canadensis} swimming across lake, Denali NP, Alaska, USA

Mary McDonald / American beaver {Castor canadensis} swimming in lake, Denali NP, Alaska, USA

Mary McDonald / American beaver {Castor canadensis} swimming across lake, Denali NP, Alaska, USA

Mary McDonald / American beaver {Castor canadensis} swimming across lake dragging branch in its mouth, Denali NP, Alaska, USA

Scott Leslie / American Beaver (Castor canadensis) lodge, Nova Scotia, Canada

Jerry Monkman / Wood chips created by American beaver {Castor canadensis} Goshen, Connecticut, USA

Jerry Monkman / Trees felled by American beaver {Castor canadensis} Acadia NP, Maine, USA

Jerry Monkman / Trees damaged by American beaver {Castor canadensis} Goshen, Connecticut, USA

Doug Wechsler / American beaver {Castor canadensis} lodge in Cranberry Lake, Adirondack Park, New York, USA

Graham Eaton / American Beaver (Castor canadensis) in lake with twig in mouth, Alaska, USA, June

Graham Eaton / North American Beaver (Castor canadensis) sitting on a log, chewing wood, Alaska, USA, June

Nature Production / American beaver's nest {Castor canadensis} Grand Teton NP, Wyoming, USA

Yva Momatiuk & John Eastcott / American Beaver (Castor canadensis) a semi-aquatic rodent swimming branches across calm pond behind beaver dam, fall evening, Denali National Park, Alaska

Thomas Lazar / American beaver on frozen cattail pond (Castor canadensis) Kettle River, USA

Michael Durham / American Beaver (Castor canadensis) building a dam at night, Mt Hood National Forest, Oregon

J Foott / American beaver {Castor canadensis} adult and young feeding on Aspen timber, Grand Teton NP, Wyoming, USA

J Foott / American beaver {Castor canadensis} adult feeding on Aspen timber, Grand Teton NP, Wyoming, USA.

J Foott / American beaver {Castor canadensis} adult feeding on Aspen timber, Grand Teton NP, Wyoming, USA

John Cancalosi / American beaver {Castor canadensis} in water, USA.

Richard Du Toit / American beaver {Castor canadensis} head profile, Grand Teton NP, USA

LYNN M. STONE / Beaver {Castor canadensis} swimming with branch, USA. Captive.

Thomas Lazar / American beaver {Castor canadensis} on ice, Kettle River, Minnesota, USA

Thomas Lazar / American beaver {Castor canadensis} Kettle River, Minnesota, USA

Thomas Lazar / American beaver {Castor canadensis} Kettle River, Minnesota, USA

Thomas Lazar / American beaver {Castor canadensis} at water's edge, Kettle River, Minnesota, USA

LYNN M. STONE / American beaver {Castor canadensis} beside tree damaged by gnawing, Minnesota, USA Captive.

LYNN M. STONE / American beaver {Castor canadensis} beside tree damaged by gnawing, Minnesota, USA Captive.

Larry Michael / Damage to tree caused by American beaver {Castor canadensis} USA

JEFF FOOTT / American beaver {Castor canadensis} Grand Teton NP, Wyoming, USA

Philippe Clement / American Beaver's lodge (Castor canadensis) in pond in tundra habitat, Denali NP, Alaska, USA.

Philippe Clement / Felled trees by American beaver {Castor canadensis} Grand Teton NP, Wyoming, USA

Philippe Clement / Close-up of American beaver teeth marks in tree trunk {Castor canadensis} Grand Teton NP, Wyoming, USA.

Philippe Clement / Tree felled by American beaver {Castor canadensis} Grand Teton NP, Wyoming, USA

Philippe Clement / American Beaver dam and den {Castor canadensis} Grand Teton NP, Wyoming, USA.

Philippe Clement / American Beaver dam {Castor canadensis} Grand Teton NP, Wyoming, USA.

JEFF FOOTT / Beaver (Castor canadensis) lodge, dam and pond, USA

JEFF FOOTT / American beaver {Castor canadensis} feeding on Aspen. Grand Teton NP, Wyoming, USA

David Kjaer / American beaver dam {Castor canadensis} Grand Teton NP, Wyoming, USA

Philippe Clement / Dam constructed by American beaver {Castor canadensis} Grand Teton National Park, Wyoming, USA

Thomas Lazar / American beaver gnawing on wood {Castor canadensis} captive, USA

Michael Durham / American Beaver (Castor canadensis) splashing water with tail in defensive display, Mt Hood National Forest, Oregon

Sumio Harada / American Beaver (Castor canadensis) building dam, Rocky Mountains, North America

Sumio Harada / American Beaver (Castor canadensis) skull, North America

Sumio Harada / American Beaver (Castor canadensis) underwater view of dam, Rocky Mountains, North America

Colin Monteath / Lenga Beech (Nothofagus pumilio) trees, felled by an American Beaver (Castor canadensis) and used to build nest mound, southern Argentina

Gerry Ellis / American Beaver (Castor canadensis) near water, Aspen Valley, Ontario, Canada

Gerry Ellis / American Beaver (Castor canadensis) pond with water lilies and forest, Chugach National Forest, Alaska