Kim Taylor / Wood white butterflies (Leptidea sinapis) at 'salt lick' beside a woodland stream, Bulgaria, July.

Pete Oxford / White-lipped peccary (Tayassu pecari) at saltlick. Yasuni National Park, Amazon Rainforest, Ecuador, South America.

Pete Oxford / White-lipped peccary (Tayassu pecari) at saltlick. Yasuni National Park, Amazon Rainforest, Ecuador, South America.

Pete Oxford / White-lipped peccary (Tayassu pecari) at saltlick. Yasuni National Park, Amazon Rainforest, Ecuador, South America.

Pete Oxford / Dusky-headed parakeet (Aratinga weddellii) at claylick. Yasuni National Park, Amazon Rainforest, Ecuador, South America.

Pete Oxford / White-lipped peccary (Tayassu pecari) at saltlick. Yasuni National Park, Amazon Rainforest, Ecuador, South America.

Pete Oxford / Red brocket deer (Mazama americana) male at saltlick. Yasuni National Park, Amazon Rainforest, Ecuador. South America.

Martin Gabriel / Tropical butterflies flying and resting at a salt-lick at the banks of a river, Corcovado National Park, Costa Rica, February

Martin Gabriel / Tropical butterflies flying and resting at a salt-lick at the banks of a river, Corcovado National Park, Costa Rica, February

Martin Gabriel / Tropical butterflies flying and resting at a salt-lick at the banks of a river, Corcovado National Park, Costa Rica, February

Fiona Rogers / Mantled Colobus (Colobus guereza) young male ingesting soil for its salts and minerals, Kakamega Forest Reserve, Kenya

Pete Oxford / Pierid Butterfly (Phoebis sp) group on mineral lick, Yasuni National Park, Amazon, Ecuador