George Sanker / American red squirrel (Tamiasciurus hudsonicus) on tree trunk drinking in a beaver pond early in the morning. Acadia National Park, Maine, USA. May.

George Sanker / Male North American red squirrel (Tamiasciurus hudsonicus) alarm calling, Yellowstone National Park, Wyoming, USA, June

Donald M. Jones / Red Squirrel (Tamiasciurus hudsonicus) on pine cone flakes, western Montana

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing babies in nest, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) climbing tree, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) curious 40 day old babies peer out from nest in tree trunk, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 19 day old babies in nest in tree trunk, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother nursing her 15 day old babies in nest, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) standing on branch, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother protecting territory near her nest from other squirrels, Rocky Mountains, North America

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) separating seeds from an Engelmann Spruce (Picea engelmannii) cone to store for winter food, Rocky Mountains, Alberta, Canada

Sumio Harada / Red Squirrel (Tamiasciurus hudsonicus) mother returning to her 35 day old babies in nest to nurse them, Rocky Mountains, North America

Michael Quinton / Red Squirrel (Tamiasciurus hudsonicus) four young at entrance to their nest in a tree cavity, Alaska

Michio Hoshino / Red Squirrel (Tamiasciurus hudsonicus) feeding atop tree stump, Alaska

George Sanker / American Red squirrel (Tamiasciurus hudsonicus) on tree trunk drinking in a beaver pond. Acadia National Park, Maine, USA.

Doug Gimesy / American red squirrel (Tamiasciurus hudsonicus) standing on branch. Grand Teton National Park, Wyoming, USA.? October.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) drinking in a beaver pond early in the morning. Acadia National Park, Maine, USA.

Tim Laman / American red squirrel (Tamiasciurus hudsonicus) climbing down tree trunk, Massachusetts, USA. April.

George Sanker / American red squirrel (Tamiasciurus hudsonicus). feeding, Acadia National Park, Maine, USA. April.

Sylvain Cordier / American red squirrel (Tamiasciurus hudsonicus) Michigan, USA, June.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) feeding in meadow. Acadia National Park, Maine, USA. May.

Francis Abbott / American red squirrel (Tamiasciurus hudsonicus) feeding on Conifer seeds in tree. Near Sunwapta Falls, Jasper National Park, Canada. June.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) feeding in fir tree. Acadia National Park, Maine, USA. May.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) feeding on Douglas Fir (Pseudotsuga menziesii) seeds in cone, Montana, USA. October.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) collecting, Douglas Fir (Pseudotsuga menziesii) cones, Montana, USA. October.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) collecting, Douglas Fir (Pseudotsuga menziesii) cones, Montana, USA. September.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) on Douglas Fir (Pseudotsuga menziesii) Montana, USA. October.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) collecting, Douglas Fir (Pseudotsuga menziesii) cones, Montana, USA.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) collecting, Douglas Fir (Pseudotsuga menziesii) cones, Montana, USA.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) feeding on Douglas Fir (Pseudotsuga menziesii) cones, Montana, USA.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) feeding on Douglas Fir (Pseudotsuga menziesii) seeds in cone, Montana, USA.

Phil Savoie / American red squirrel (Tamiasciurus hudsonicus) Montana, USA.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus) resting on fallen birch tree. Acadia National Park, Maine, USA.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus). Feeding in fir tree. Acadia National Park, Maine, USA.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus). Resting on birch tree. Acadia National Park, Maine, USA.

Charlie Summers / Albino American red squirrel (Tamiasciurus hudsonicus) eating a pine cone from a Ponderosa pine (Pinus ponderosa) Taylor Park, San Isabel National Forest, Colorado, USA.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) chewing on freshwater mussel shell, Acadia National Park, Maine, USA

Connor Stefanison / American Red squirrel (Tamiasciurus hudsonicus) climbs around a tree in Jasper National Park, Alberta, Canada, December

Charlie Summers / American red squirrel (Tamiasciurus hudsonicus) albino with a Ponderosa pine (Pinus ponderosa) cone, Taylor Park, Colorado, USA, August.

Charlie Summers / American red squirrel (Tamiasciurus hudsonicus) albino with a Ponderosa pine (Pinus ponderosa) cone,Taylor Park, Colorado, USA, August.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) in snow, Acadia National Park, Maine, USA. February.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) on hind legs, Acadia National Park, Maine, USA. May.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) climbing on tree trunk Acadia National Park, Maine, USA.

George Sanker / American red squirrel (Tamiasciurus hudsonicus) on tree trunk, Acadia National Park, Maine, USA.

George Sanker / American Red Squirrels (Tamiasciurus hudsonicus) running past each other, Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus) on tree trunk, Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus) peering out of hole, feeding, Grand Teton National Park, Wyoming, USA, June.

George Sanker / American Red Squirrel (Tamiasciurus hudsonicus). Acadia National Park, Maine, USA, October