Rats and Extinctions

A repost from this blog circa August 2004.

Believe it or not, rats have been responsible for more species extinctions than anything else. The reason for this is that so many of the animals that have been pushed into extinction have been indigenous ground-nesting birds living on small islands. Once rats are introduced in these locations, eggs and hatchlings are predated upon, bird populations plummet, and extinction often follows.

Rats have been eradicated from islands only a few times, and in all occasions, it has involved a tremendous amount of poison bait used for a long time.

It's worth remembering that the rat is a survivor -- they survived the nuclear blasts on Pacific atolls and actually prospered under those conditions, living on dead creatures and plant life that washed up on the beach.

One of the few examples of successful rat eradication on an island is Campbell Island, south of New Zealand. Rats got to the island via whaling ships, and destroyed the nesting grounds of the flightless teal and wading duck.

In 2002 the government of New Zealand used 120 TONS of rat poison on the island (over 240,000 pounds), delivered by boat and helicopter. About 200,000 rats died, but not without some mishap. A tanker carrying 18 tons of rat poison sank in a whale breeding ground, and there was some mild (and probably temporary) contamination of the local mussel population.

In any case, the rats are now gone, the whales are OK, and so too are the mussels. The teal and ducks are set to be re-introduced from captive populations. This is a very rare example of success in the war against rats.
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