Klein & Hubert / Hippopotamus (Hippopotamus amphibius) with Red-bellied oxpeckers (Buphagus erythrorhynchus) on his head in river, Luangwa National Park, Zambia

Guy Edwardes / Red-billed oxpecker (Buphagus erythrorhynchus) feeding on Impala (Aepyceros melampus), Savuti, Botswana.

Ann & Steve Toon / Impala (Aepyceros melampus) with redbilled oxpecker (Buphagus erythrorhynchus), Kruger National Park, 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 / 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.

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) on Impala (Aepyceros melampus) male, Kruger National Park, South Africa

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) on Burchell's Zebra (Equus burchellii), Mkhuze Game Reserve, KwaZulu-Natal, South Africa

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

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) landing on South African Giraffe (Giraffa giraffa giraffa), KwaZulu-Natal, South Africa

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) group on Warthog (Phacochoerus africanus), Kruger National Park, South Africa

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) group on White Rhinoceros (Ceratotherium simum), Kruger National Park, South Africa

Richard Du Toit / Red-billed Oxpecker (Buphagus erythrorhynchus) group on White Rhinoceros (Ceratotherium simum), Kruger National Park, South Africa

Richard Du Toit / Impala (Aepyceros melampus) male with Red-billed Oxpecker (Buphagus erythrorhynchus) pair, Kruger National Park, South Africa

Heini Wehrle / Red-billed Oxpecker (Buphagus erythrorhynchus) pair searching for parasites on Impala, Mpumalanga, South Africa

Sergey Gorshkov / Red-billed Oxpecker (Buphagus erythrorhynchus) trio on White Rhinoceros (Ceratotherium simum), Sabi-sands Game Reserve, South Africa

Richard Du Toit / Hippopotamus (Hippopotamus amphibius) male with Red-billed Oxpecker (Buphagus erythrorhynchus) pair on back, Chobe National Park, Botswana

Yva Momatiuk & John Eastcott / Cape Buffalo (Syncerus caffer) bull with Red-billed Oxpecker (Buphagus erythrorhynchus) pair, Masai Mara National Reserve, Kenya

Mitsuaki Iwago / Cape Buffalo (Syncerus caffer) eyeing Red-billed Oxpecker (Buphagus erythrorhynchus), Serengeti National Park, Tanzania

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

Mitsuaki Iwago / Black Rhinoceros (Diceros bicornis) with Red-billed Oxpecker (Buphagus erythrorhynchus), Serengeti National Park, Tanzania

Klein & Hubert / Three red-bellied oxpeckers (Buphagus erythrorhynchus) on the back of a Hippopotamus (Hippopotamus amphibius) in a river, Luangwa National Park, Zambia, Africa.

Klein & Hubert / Hippopotamus (Hippopotamus amphibius) sleeping in the Luangwa River in dry season with billed oxpeckers (Buphagus erythrorhynchus) cleaning his skin, South Luangwa National Park, Zambia, Africa.

Guy Edwardes / Red-billed oxpecker (Buphagus erythrorhynchus) adult and juvenile sunbathing in sand. Savuti, Botswana.

Guy Edwardes / Red-billed oxpecker (Buphagus erythrorhynchus) feeding on parasites in ear of Impala (Aepyceros melampus). Savuti, Botswana.

Tui De Roy / Black rhino (Diceros bicornis) mother with wounds and Red-billed oxpeckers (Buphagus erythrorhynchus) and calf walking up a slope, Solio Game Reserve, Laikipia, Kenya. October.

Klein & Hubert / African buffalo drinking (Syncerus caffer) at water hole in dry season and Red-billed oxpecker (Buphagus erythrorhynchus) on head. South Luangwa National Park, Zambia.

Klein & Hubert / African buffalo (Syncerus caffer) drinking at water hole in dry season and Red-billed oxpeckers (Buphagus erythrorhynchus) on head, South Luangwa National Park, Zambia.

Klein & Hubert / African buffalo (Syncerus caffer) drinking at water hole in dry season and Red-billed oxpeckers (Buphagus erythrorhynchus) on head, South Luangwa National Park, Zambia.

Ann & Steve Toon / Warthog (Phacochoerus africanus) with Redbilled oxpecker (Buphagus erythrorhynchus), Zimanga game reserve, KwaZulu-Natal, South Africa.

Ann & Steve Toon / Warthog (Phacochoerus africanus) drinking, with redbilled oxpeckers (Buphagus erythrorhynchus), Zimanga game reserve, KwaZulu-Natal, South Africa.

Ann & Steve Toon / Warthog (Phacochoerus africanus) drinking, with redbilled oxpecker (Buphagus erythrorhynchus), Zimanga game reserve, KwaZulu-Natal, South Africa.

Ann & Steve Toon / Redbilled oxpecker (Buphagus erythrorhynchus) searching for insects on Warthog (Phacochoerus africanus), Zimanga game reserve, KwaZulu-Natal, South Africa.

Ann & Steve Toon / Redbilled oxpecker (Buphagus erythrorhynchus) drinking from perch on warthog, Zimanga private game reserve, KwaZulu-Natal, South Africa.

Melvin Grey / Cape buffalo (Syncerus caffer caffer) portrait, Red-billed oxpeckers (Buphagus erythrorhynchus) removing parasites. Nakuru, Kenya.

Staffan Widstrand / Common Warthog (Phacochoerus africanus), with a Red-billed Oxpecker (Buphagus erythrorhynchus) eating its ticks and other parasites, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

Staffan Widstrand / Common Warthog (Phacochoerus africanus), with a Red-billed Oxpecker (Buphagus erythrorhynchus) eating its ticks and other parasites, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

Staffan Widstrand / RF - African buffalo / Cape buffalo (Syncerus caffer) with Red billed oxpecker (Buphagus erythrorhynchus) drinking at waterhole, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

Klein & Hubert / Hippopotamus (Hippopotamus amphibius) with Red-billed oxpeckers (Buphagus erythrorhynchus) taking off from back, entering water in the Luangwa River, Luangwa National Park, Zambia

Klein & Hubert / Red-bellied oxpeckers (Buphagus erythrorhynchus) feeding on a wound on hippo's back., Luangwa National Park, Zambia

Klein & Hubert / Hippopotamus (Hippopotamus amphibius) with Red-bellied oxpeckers (Buphagus erythrorhynchus) on back, entering water in the Luangwa River, Luangwa National Park, Zambia

Klein & Hubert / Hippopotamus (Hippopotamus amphibius) with Red-bellied oxpeckers (Buphagus erythrorhynchus) on back, entering water in the Luangwa River, Luangwa National Park, Zambia

Ann & Steve Toon / Redbilled oxpecker (Buphagus erythrorhynchus) on Impala (Aepyceros melampus), iMfolozi game reserve, KwaZulu-Natal, South Africa, September

Ann & Steve Toon / Redbilled oxpecker (Buphagus erythrorhynchus) on Impala (Aepyceros melampus), iMfolozi game reserve, KwaZulu-Natal, South Africa, September

Ann & Steve Toon / Giraffe (Giraffa camelopardalis) with Red-billed oxpeckers (Buphagus erythrorhynchus), Zimanga private game reserve, KwaZulu-Natal, South Africa, June.

Eric Baccega / Four Burchell's zebra (Equus quagga burchellii) two with Red billed oxpeckers (Buphagus erythrorynchus) on their backs, with Antelope, mainly Impala (Aepyceros melampus) and a Warthog (Phacochoerus af...

Jen Guyton / Common eland (Taurotragus oryx) with Red-billed oxpeckers (Buphagus erythrorhynchus) and yellow-billed oxpecker (Buphagus africanus) standing on the savanna in the Maasai Mara Reserve, Kenya.