Identification and management of a single large population of wild dromedary camels

The dromedary camel (Camelus dromedarius) is a significant invasive species in Australia. It is an unusual pest species that is of large body size with relatively low fecundity compared with other pest species. Camels are highly adapted to the arid regions that characterize a large proportion of Australia and occupy an almost completely undisturbed area of ≥3 million km 2. They have no history of invasion elsewhere in the world. Despite this, their population has been expanding at approximately 80,000 camels per annum, with the most recent estimate of population size around 1,000,000 individuals. We employed a landscape-genetic approach to evaluate the population structure and molecular ecology of Australian camels. We combined mitochondrial control region sequence (n = 209 animals) with 18 microsatellite markers to profile over 800 adult camels to identify the presence of a single panmictic population. We showed that demographically defined neighborhoods for wild camels are about 200 km; this value was supported by home range estimates. Distances greater than this display no pattern of isolation by distance across the Australian continent. The result is the largest single geographical population so far recorded for an invasive species in Australia. This pattern may be explained by the impressive and near-nomadic dispersal pattern of camels, in combination with an unpredictable environment virtually devoid of barriers to movement and predatory suppression. Although it is technically feasible, the reality is that it would not be economically or politically viable to have continental eradication of wild camels in Australia because of the vast size and movement dynamics of the camel population. As such, we advocate a change away from an expensive solution to an intractable reduction program (that is almost entirely focused on protection of biological refugia) and moves to include cultural, economic, and biodiversity asset protection for the management of this most unorthodox of invasive species.