Denis-Huot / Masai giraffe (Giraffa camelopardalis tippelskirchi) two silhouetted at sunrise, Maasai Mara Game Reserve, Kenya.

Will Burrard-Lucas / Three Ethiopian wolf (Canis simensis) pups waiting for their parents to return, Ethiopia.

John Cancalosi / Cross-Section of Utah Septarian Nodule, Utah. A type of geode, Utah Septarian Nodules are found about 15 miles east of Zion National park. They were formed in an ancient sea floor during the Cretaceou...

Bence Mate / Silhouette of an African leopard (Panthera pardus pardus) snarling, Mkuze, South Africa. September. 'White Fang' - this leopard bared its fangs to the hyenas threatening his prey. Eventually the leopa...

Ingo Arndt / Aerial view of Hardy Reef, Great Barrier Reef, Queensland, Australia, December 2010.

Erlend Haarberg / Mountain hare (Lepus timidus) breath backlit during cold night, Vauldalen, Norway May

Loic Poidevin / Red deer (Cervus elaphus) male stag silhouetted at dusk, rut season, Jura, Scotland, UK, September

Tony Wu / Giant frogfish (Antennarius commersoni) silhouetted against sea surface from below, Ambon, Indonesia.

Franco Banfi / Giant manta ray (Manta birostris) seen from above, Revillagigedo Archipelago Biosphere Reserve, Socorro Islands, Western Mexico

Mike Read / Norway maple (Acer platanoides) seeds on lightbox, Ringwood, Hampshire, UK October

Andy Trowbridge / Eurasian Eagle owl (Bubo bubo) silhouetted at dawn, perched on rocky outcrop. Southern Norway. August.

Denis-Huot / Masai giraffe (Giraffa camelopardalis tippelskirchi) two on horizon at sunrise, Maasai Mara Game Reserve, Kenya

Denis-Huot / Masai giraffe (Giraffa camelopardalis tippelskirchi) group on horizon at sunrise, Maasai Mara Game Reserve, Kenya

Rhonda Klevansky / Shadow of person with surfboard walking on beach, Durban, KwaZulu-Natal, South Africa, August, 2009.

Andy Rouse / African Lion (Panthera leo) outline of female, Masai Mara, Kenya

Juergen Freund / Aerial view of Hardy Reef, Great Barrier Reef, August 2011

Daniel Nunez / Imitating poison frog (Ranitomeya imitator) resting on leaf, Tarapoto, Peru. Cropped.

Lucas Bustamante / Puma (Puma concolor) backlit at sunrise, Torres del Paine National Park, Magallanes, Chile.

Ingo Arndt / Trees in snow, Hessen, Germany. January.

David Fleetham / Gold dust day gecko (Phelsuma laticauda) silhouetted on leaf, an invasive species, peering over the edge of ginger leaf, Hawaii.

Andy Rouse / RF - African elephant (Loxodonta africana) silhouette at sunset, Maasai Mara, Kenya, Africa. (This image may be licensed either as rights managed or royalty free.)

Andy Rouse / African lion (Panthera leo) female silhouetted, yawning at dawn, Masai Mara, Kenya, Africa.