Jaymi Heimbuch / Yellow-billed Oxpecker (Buphagus africanus) picking parasites off of Cape Buffalo (Syncerus caffer), Masai Mara, Kenya

Neil Aldridge / Yellow-billed oxpecker (Buphagus africanus) perched on the back of an African buffalo (Syncerus caffer) on the banks of the Chobe River, Chobe National Park, Botswana.

Neil Aldridge / Warthog (Phacochoerus africanus) with a Yellow-billed oxpecker (Buphagus africanus) on its back, nuzzling its mother at a waterhole, Chief's Island, Okavango Delta, Botswana.

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.

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

Pal Hermansen / Yellow-billed oxpecker (Buphagus africanus) on African buffalo (Syncerus caffer), Masai Mara, Kenya

Shin Yoshino / Yellow-billed Oxpecker (Buphagus africanus) trio sitting on Cape Buffalo's (Syncerus caffer) head, Kenya

Mitsuaki Iwago / Hippopotamus (Hippopotamus amphibius) with Yellow-billed Oxpecker (Buphagus africanus), Serengeti National Park, Tanzania

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

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.