"Our research is giving us a better understanding of the impacts of introduced rats, and by working directly with government agencies and nongovernmental organizations we're able to do something about it," Croll said.
The study describes an elegant example of an ecological phenomenon known as a trophic cascade. "In a trophic cascade, you have an apex predator--in this case, the rat--and because of what that predator eats, you get a cascade of effects that go down through lower levels of the food chain," Kurle said. "This is a clear example of a trophic cascade that crosses between terrestrial and marine ecosystems."
Kurle spent three summers conducting intertidal surveys on 32 islands in the Aleutian Archipelago--17 with rats and 15 without. At first, camping on rat-infested islands was disconcerting, she said. She had to wear ear plugs the first few nights because the sound of rats rustling around outside the tent was keeping her awake. But she soon got used to it.
"We had to be careful with food and trash, but they never got into the tent or anything," Kurle said. "They come out as soon as it starts to get dark, and we would see them running around everywhere. We spent several nights watching them through night-vision binoculars."
The researchers found large numbers of dead birds partially eaten by rats on the islands. The rats mainly attack the chicks, but may also go after adults, Kurle said. Very few birds manage to breed successfully on the rat-infested islands.
Another recent paper from Croll and Tershy's group provides a global overview of the direct effects of invasive rats on seabirds. Published in the February issue of Conservation Biology, the paper reviews the findings of 94 published studies. First au
|Contact: Tim Stephens|
University of California - Santa Cruz