Ecological disaster prompts biggest-ever rat hunt

February 26th, 2008 - 11:33 am ICT by admin  

New York, Feb 26 (IANS) The biggest-ever rat hunts will begin this summer, prompted by grave concerns over the decimation of nesting seabird colonies on the Aleutian islands of the north Pacific. The threat to the bird colonies have been seen on islands that did not have rodent populations till they were introduced, in one way or the other, by humans.

The rats mainly attack the chicks, but may also target adults on these islands, where the birds mostly nest on the ground. Very few birds manage to breed successfully on these rat-infested islands.

The rat attacks have consequences that go beyond the extermination of birds - their presence also leads to other ecological changes, a new study has found.

For instance, on the Aleutian archipelago, it has resulted in a dramatic alteration of the inter-tidal zone, dwindling seaweed and greater numbers of snails and barnacles.

“When you’re on an island with rats, there are so few birds it’s silent, in contrast to the cacophony on the islands without rats,” said Carolyn Kurle of the University of California, who led the study.

Kurle spent three summers conducting inter-tidal surveys on 32 islands in the Aleutian archipelago - 17 with rats and 15 without.

Some of the affected birds - sea gulls and oystercatchers, in particular - are major predators of invertebrates in the inter-tidal zone.

Their absence caused snails, limpets and other grazers to proliferate, eat more algae, and clear more space for other invertebrates to settle and grow.

The result has been a shoreline practically stripped bare of the usual cover of fleshy algae - or seaweed.

Kurle and co-author Donald Croll said that their study showed “rats preyed on 75 species of seabirds in 10 families on islands throughout the world. The hardest hit seabirds are the small, hole-nesting species like petrels and auklets”.

The good news is that rats have been removed from more than 274 islands, according to the Nature Conservancy.

The study is being published in the latest issue of the Proceedings of the National Academy of Sciences.

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