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)

Espen Bergersen / Aerial shot of Killer whales (Orcinus orca) near the surface, showing mating behaviour including a male Killer whale displaying penis, Troms, Norway, August.

Franco Banfi / Sperm whale (Physeter macrocephalus) young male trying to copulate with a female. The calf of the female was in the way so the male is trying to chase it away. Dominica.

Dave Bevan / Female Giant wood wasp (Uroceras gigas) inserting ovipositor into tree stump to lay eggs, Carmarthenshire, Wales, UK, September.

Francois Savigny / Tiger male carrying Chital deer kill, Bandhavgarh NP, Madhya Pradesh, India

Tony Wu / Humpback whale (Megaptera novaeangliae) male with his penis extended. Vava'u, Tonga. South Pacific.

Alex Mustard / Black hamlet (Hypoplectrus nigricans) and Yellowbelly hamlet (Hypoplectrus aberrans) spawning at dusk. As this genus is quite recently evolved hybridization is still possible. Hamlets are one of the...

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Pete Oxford / Glass Frog (Hyalinobatrachium aureoguttatum) underside showing internal organs, native to South America

Yukihiro Fukuda / Japanese macaque (Macaca fuscata fuscata) rare white furred baby jumping, Jigokudani Valley, Nagano Prefecture, Japan. June.