The history of humans introducing non-native animal species to new lands is a long and glorious one. Some of the more notable successes include Africanized honey bees, which were introduced to the Americas in 1957 for the purpose of inspiring apocalyptic urban myths and low-budget horror films, and rabbits, which were set free in Australia in 1859 to inspire lazy Australians to get off their duffs and build a 2,021-mile rabbit-proof fence.
Typically, there is nothing to worry about when introducing new species. As Thomas Austin, the man who first released rabbits in Australia, said, “The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting.” Obviously — rabbits being rabbits — if you release a mere 24 specimens, as Austin did, there is little chance that their numbers will get out of hand. It’s not like they’re famous for breeding quickly or anything.
Sadly, however, we seem to have found one place in the world where the introduction of non-native species has had unintended negative consequences: Macquarie Island. I realize this comes as a shock to many of you, seeing as how other island chains like Guam and New Zealand have had such success with things like the brown tree snake and the common bushtail possum, respectively. Rest assured, though, that scientists, who never make incorrect decisions in these matters, have the situation on Macquarie well in hand.
For those of you unfamiliar with the place, Macquarie Island is a 50-square-mile speck of land in the Southern Ocean about halfway between Australia and Antarctica. A breeding ground for almost four million seabirds, including some 850,000 pairs of royal penguins, Macquarie was named a World Heritage site by the United Nations in 1997.
The island was first discovered in 1810, and soon after, as a Los Angeles Times story noted, “seafarers began visiting it to slaughter fur seals, elephant seals and penguins for their fur and blubber.” Penguins, as you know, are renowned for their thick, luxurious fur and, due to their massive size, can yield many tons of blubber each. While the intentions of the first seafarers were all good — unless, of course, one happened to be a seal or a penguin — they unfortunately brought some unwelcome guests with them. Rats and mice that had stowed away on the ships took up residence on Macquarie and began devastating food stores on the island.
In 1818, sailors started doing what anyone with a rat and mouse problem would do: they brought cats to the island. The cats thrived and soon had managed to bring the rodent population under control. So buoyed were seafarers by the success of the cat introduction that, in what apparently used to be a common tradition, they started bringing rabbits to the island some 60 years later to provide a food source for stranded sailors. As you might imagine, the rabbits also thrived, despite being the main food source for the cats.
Over time, the rabbit population grew to as many as 130,000 individuals, which wreaked havoc with the island’s plant life, so scientists decided it would be best to diminish their numbers. In 1968, they introduced the Myxomatosis virus, which is lethal to rabbits, and the European rabbit flea, which spreads it. By the 1980s the rabbit population was down to about 10,000.
That, however, left the cats with no choice but to feed on native birds, leading to the extinction of at least two species. Faced with this untenable situation, scientists figured they had to intervene once again, and they started shooting the cats. By 2000, there were no felines left on Macquarie.
Just last week, though, to researchers’ surprise, it was reported that, with no cats to eat them, rabbits had proliferated once again, despite the presence of the virus. In the last eight years the population has soared to an estimated 100,000, and the voracious rodents have stripped the plants bare on as much as 40 percent of the island, leading to landslides that have wiped out bird nesting sites.
As a result of all this, scientists now have no choice but to attempt to eradicate all the rabbits, mice and rats on the island, which could take years and cost as much as $17 million. Thankfully, though, as Macquarie’s history has shown, these sorts of plans are always foolproof, so at least it will be money well spent.