Some animals are so iconic of their homeland that they seem bizarrely out of place when transplanted to a new environment.
Populations of wallabies inhabit Britain. In the 1930’s, Colonel Courtney Brocklehurst, a former Chief Game Warden in the Sudan, had the Red-necked Wallabies from his private zoo in the Peak District released from captivity. The wallabies grew in number to more than fifty by the 1960s (the colonel’s three yaks released at the same time didn’t fare so well – they died out in the 1950s). The population then declined and by 2000 they were thought to be extinct, but recent sightings have confirmed that at least one remains.
There are also wild colonies on the Isle of Man and Inchconnachan Island in Scotland and occassional sightings are reported from other parts of Britain. Other afflicted areas are Lambay Island (Ireland), Rambouillet Forest (France), Hawaii and possibly Japan. But the land that has suffered most from wallaby invasions is New Zealand; at least five different species are established there and some regions have been virtually over-run by wallabies where they are considered pests.
Feral camels are a major environmental problem in Australia. Introduced in the nineteenth century as a beast of burden in the arid central regions, there are now an estimated one million camels in Australia with a doubling time of nine years. It is the largest feral camel population in the world and Australia is the world’s largest exporter of camels.
Pablo Escobar was perhaps the world’s most successful criminal. At his height in the late 1980s, he had amassed a fortune worth $25 billion and controlled 80% of the world’s cocaine market. His home, Hacienda Napoles in Columbia included a private zoo. After Escobar died in a gunfight with police in 1993, the four hippos in the zoo were left untended. By 2009, their numbers had grown to over twenty and escaped hippos were posing a threat to humans. As far as I know, they’re still there.
In 2008, salmon fisherman Guy Demert had an unusual catch. Amongst the fish was a live, healthy Humboldt Penguin. Demert was off the coast Alaskan coast, 10,000 km from the penguin’s natural range.
Penguins have been known of in the Northern Hemisphere for a long time. Twenty thousand year-old paintings in the Cosquer Caves off the coast of France depict penguins, indicating that they existed much further north during the Last Glacial Maximum than they do today. The only current species of penguin that travels to the Northern Hemisphere of its own accord is the Galapagos Penguin whose habitat straddles the equator.
However, occassionally penguins are found well beyond their natural range. In a 2007 paper, A. N. Van Burren and P. Dee Boersma note four penguin sightings off the US coast since 1944. They make the case that these northern penguins were most likely picked up in southern waters by sailors, kept for awhile as pets, then released in the north. They conclude that the likelihood of penguins establishing a sustainable population in the Northern Hemisphere is low largely due to the presence of predators such as bears and eagles. Three attempts to introduce penguins to Norway in the 1930s and 1940s failed.