Morley Read / Close-up of Agua rica leaf frog (Phyllomedusa ecuatoriana) eggs after 11 days development, showing beating heart and blood flowing over gills, Ecuador. Endangered. (non-ex)

Morley Read / Developing embryo of the Ecuadorian monkey frog (Phyllomedusa ecuatoriana), showing heart beating and blood flowing, Morona Santiago Province, Ecuador, (non-ex)

Daniel J. Cox / Gray Wolf (Canis lupus) predating female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 4 of 4

Daniel J. Cox / Gray Wolf (Canis lupus) killing female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 3 of 4

Daniel J. Cox / Gray Wolf (Canis lupus) attacking female Elk (Cervus elaphus) crossing river, Alum Creek, Yellowstone National Park, Wyoming, sequence 2 of 4

Agustin Esmoris / Southern Elephant Seal (Mirounga leonina) male calling and bleeding after fight, Puerto Madryn, Argentina

Espen Bergersen / Gulls (Laridae) seaching for food in water containing blood coming from a large fishing boat, Tromvik, Kvaloya, Troms, Norway, November 2014.

Bryan and Cherry Alexander / Chukchi girls, with their family's ancestral clan mark painted in reindeer blood on their face, a ritual during the Chukchi 'Festival of the Young Reindeer' during which young reindeer are sacrificed....

Piotr Naskrecki / Yellow Fever Mosquito (Aedes aegypti) female feeding on human blood, Gorongosa National Park, Mozambique

Dong Lei / Blood pheasants (Ithaginis cruentus) foraging in habitat, one looking at the camera, Meli Snow Mountain National Park, Yunnan Province, China, January. Endemic. Taken with remote camera.

Nick Upton / Bloody-nosed beetles (Timarcha tenebricosa) mating on a grass stem in a chalk grassland meadow, Wiltshire, UK, April.

Jabruson / Hammer Headed bats (Hypsignathus monstrosus) in gloved hand - live mist net catch for blood sampling in search of the unknown reservoir host for Ebola virus. Ebola outbreaks in Mbomo in 2003 killed 12...