Matthias Breiter / Polar Bear (Ursus maritimus) adult male charging opponent, Churchill, Manitoba, Canada

Fred Bavendam / Giant Nudibranch (Dendronotus iris) attacking a Tube-dwelling Anemone (Pachycerianthus fimbriatus), Vancouver Island, British Columbia, Canada. Sequence 4 of 5

Michio Hoshino / Polar Bear (Ursus maritimus) males fighting, Churchill, Manitoba, Canada

Yva Momatiuk & John Eastcott / Northern Gannet (Morus bassanus) pair aggressively defending their territory in breeding colony, summer, Newfoundland, Canada

Thomas Mangelsen / Polar Bear (Ursus maritimus) pair sparring, near Churchill, Manitoba, Canada

Flip Nicklin / Polar Bear (Ursus maritimus) near carcass with camp dogs surrounding it, Canada

Flip Nicklin / Polar Bear (Ursus maritimus) pair sparring, Churchill, Manitoba, Canada

Fred Bavendam / Giant Nudibranch (Dendronotus iris) attacking a Tube-dwelling Anemone (Pachycerianthus fimbriatus), Vancouver Island, British Columbia, Canada. Sequence 3 of 5

Flip Nicklin / Narwhal (Monodon monoceros) fighting males with crossed tusks, Baffin Island, Canada

Michio Hoshino / Polar Bear (Ursus maritimus) males fighting, Churchill, Manitoba, Canada

Michio Hoshino / Polar Bear (Ursus maritimus) males fighting, Churchill, Manitoba, Canada

Michio Hoshino / Polar Bear (Ursus maritimus) males fighting, Churchill, Manitoba, Canada