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 / 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.

Ann & Steve Toon / Redbilled oxpecker (Buphagus erythrorhynchus), Zimanga private game reserve, KwaZulu-Natal, South Africa, June

Eric Baccega / Portrait of Masai giraffe (Giraffa camelopardalis tippelskirchi) with Redbilled oxpeckers (Buphagus erythrorhynchus) on neck, Akagera National Park, Rwanda, Africa

Denis-Huot / Greater kudu (Tragelaphus strepsiceros) female with Red-billed oxpecker (Buphagus erythrorhynchus), Sabi Sands Private Game Reserve, South Africa.

Ernie Janes / Impala (Aepyceros melampus) with Red-billed oxpecker (Buphagus erythrorhynchus) , KwaZulu-Natal, South Africa.

Wim van den Heever / Red-Billed oxpecker (Buphagus erythrorhynchus) having a drink, taken from eye level hide, Zimanga Private Game Reserve, South Africa

Will Burrard-Lucas / Rhodesian / Thornicroft giraffe (Giraffa camelopardalis thornicrofti) portrait, with Red-billed oxpeckers (Buphagus erythrorhynchus) on neck, South Luangwa National Park, Zambia, April.

Pete Oxford / Giraffe (Giraffa camelopardalis) with Red billed oxpecker (Buphagus erythrorhynchus) on head, Marakele Private Reserve, Waterberg Biosphere Reserve, Limpopo Province, South Africa.

Konrad Wothe / Red billed oxpecker (Buphagus erythrorhynchus) perched on Reticualted giraffe (Giraffa camelopardalis reticulata) neck, Samburu Game Reserve, Kenya, East Africa, August.

Konrad Wothe / Red billed oxpecker (Buphagus erythrorhynchus) perched on Reticualted giraffe (Giraffa camelopardalis reticulata) neck, Samburu Game Reserve, Kenya, East Africa, August.

Ann & Steve Toon / Warthog (Phacochoerus aethiopicus), with adult and juvenile Redbilled oxpeckers (Buphagus erythrorhynchus) Mkhuze Game Reserve, KwaZulu-Natal, South Africa, June

Ann & Steve Toon / Red-billed oxpecker (Buphagus erythrorhynchus), Zimanga Private Game Reserve, KwaZulu-Natal, South Africa, May

Richard Du Toit / Red-billed oxpecker (Buphagus erythrorhynchus) on back of South African giraffe (Giraffa camelopardalis giraffa), Itala Game Reserve, KwaZulu-Natal.

Denis-Huot / African buffalo (Syncerus caffer) male with red-billed oxpecker (Buphagus erythrorhynchus), Masai Mara Game Reserve, Kenya, October.

Ann & Steve Toon / Plains zebra (Equus burchelli) with redbilled oxpecker (Buphagus erythrorhynchus), Kruger National Park, South Africa.

Ann & Steve Toon / Hippopotamus (Hippopotamus amphibius) group on land with red billed oxpeckers (Buphagus erythrorhynchus), Kruger National park, Mpumalanga, South Africa.

Charlie Summers / Masai giraffe (Giraffa camelopardalis tippelskirchi) male with red-billed (Buphagus erythrorhynchus) and yellow-billed (Buphagus africanus) oxpeckers on neck, Ruaha National Park, Tanzania.

Pal Hermansen / Black rhinceros (Diceros bicornis) and Red-billed oxpeckers (Buphagus erythrorhynchus) Masai Mara, Kenya.