 Because the fly depends on the rhinoceros for reproduction, its numbers declined steeply as the black and white rhinos faced extinction.Like the rhinoceros, it must once have spread across much of sub-Saharan Africa (outside of the Congo Basin), but is today restricted to the savannas of southern and eastern Africa.The fly was originally described by English naturalist Sir Richard Owen in 1830 under the name of "Oestrus rhinocerontis".