The introduction of non-native species can be a tricky business. The feral camels of Australia are a case in point. They were brought to the country in 1840 to ease exploration of the Outback, and the hardy animals soon proved useful in the construction of railway and telegraph lines.

From the beginning, however, camels and Australia made for a precarious pairing. During one of the first Australian expeditions to use the beasts–John Horrocks’ 1846 journey into the Outback–a camel was responsible for the expedition leader’s death. Horrocks was unloading a rifle while standing alongside a prone pack camel when the camel suddenly lurched, hooking part of its pack into the rifle’s action. The gun discharged, and the slug severed Horrocks’ middle finger, then entered through his left cheek and knocked out a row of upper teeth. Horrocks died within the month, but not before ordering the camel executed.

On a large scale, Australian camels started to create trouble in the 1930s, when automobiles rendered them increasingly obsolete. The thousands of no-longer-needed animals multiplied rapidly, given plenty of space and camels’ suitability for the dry climate. Their population approximately doubled every eight years, and by 2008 they numbered an estimated 600,000. Australia is now the only country with a substantial feral camel population.

The huge numbers of wild camels have become a major ecological and financial liability. They deplete vegetation and water sources, creating scarcity for other animals. The feral camels are particularly ravenous when searching for water, tearing up water spigots and toilet blocks in the process. They also destroy other types of infrastructure, from fences to windmills. Camels have even become a traffic hazard, both on highways and on airplane runways.

Efforts are underway to de-camelize the continent, a program that has met with some controversy. Researchers have started using “Judas camels” to thin the camel population, which involves placing a tracking device on a sociable camel, who then unwittingly leads the trackers to groups of feral camels. Riflemen then thin the herd from helicopters. Wild camel meat is exported to the Middle East to help offset the cost of the culling. Since 2008 camel populations have been reduced considerably.