Distribution and density of oxpeckers on giraffes in Hwange National Park, Zimbabwe

Abstract

Oxpeckers (Buphagus sp.) are two bird species closely associated to large mammals, including giraffes (Giraffa camelopardalis). We tested whether oxpeckers distributed themselves at random across individuals or aggregated on individual giraffes, and if birds select the hosts body parts with the expected greatest amount of ticks. By counting oxpeckers on giraffes body from photographs, we quantified the distribution of birds per hosts and over predefined zones on the giraffe body. Oxpeckers displayed a strong aggregation behaviour with few hosts carrying many birds while many carried a limited number or no birds, a pattern that was most exaggerated for males. Oxpeckers were disproportionately found on the mane and back, where the density of ticks is presumably the highest. This high aggregation level of birds is typical of parasitic species and could suggest that oxpecker distribution may mirror the distribution of ticks, their primary food resource, on giraffes. Abundance of ticks appears as a major driver of the oxpecker foraging behaviour, and the oxpecker-large herbivores system proves to be highly relevant for the study of host-parasite dynamics.