Richard Du Toit / Northern Giraffe (Giraffa camelopardalis) with Red-billed Oxpeckers (Buphagus erythrorhynchus) feeding on parasites in symbiotic relationship, Mkhuze Game Reserve, KwaZulu-Natal, South Africa

Pete Oxford / White Rhinoceros (Ceratotherium simum) mother and calf with Red-billed Oxpeckers (Buphagus erythrorhynchus), South Africa

Neil Aldridge / Red-billed oxpeckers (Buphagus erythrorhynchus) adult and young on the back of Common warthog (Phacochoerus africanus) through grassland in summer Mapungubwe National Park, South Africa.

Richard Du Toit / Greater kudu (Tregalaphus strepsiceros) covered in Yellowbilled oxpeckers (Buphagus africanus) rear view, Kruger National Park, South Africa.

Nick Garbutt / Adult male Hippopotamus (Hippopotamus amphibius) posturing in agressive 'yawn' behaviour, Luangwa River, South Luangwa National Park, Zambia, November

Tony Heald / Hippopotamus {Hippopotamus amphibius} with Red billed oxpeckers on head, Moremi Wildlife Reserve, Botswana

Anup Shah / Reticulated giraffe {G. c. reticulata} with oxpeckers, Masai Mara Kenya

Mitsuaki Iwago / Black Rhinoceros (Diceros bicornis) mother and baby with Red-billed Oxpeckers (Buphagus erythrorhynchus), Ngorongoro Crater, Tanzania

Richard Du Toit / Red billed oxpecker on Buffalo head, Kruger NP South Africa

Richard Du Toit / Red billed oxpecker looking for insects on Common zebra, Kruger NP, South Africa.

Tony Heald / Impala with Oxpeckers. Kruger National Park, South Africa

Sharon Heald / Yellowbilled oxpecker {Buphagus africanus} on Zebra Moremi WR, Botswana, Africa