Washington, Feb 22 : A new report has indicated that invasive rats on ocean islands are threatening the survival of many of the world's seabirds.
According to a report in National Geographic News, the global analysis found that non-native rats have been observed preying on roughly a quarter of all seabird species, often with disastrous consequences.
Experts have suggested that the rat invasions have been caused particularly by three rats species native to Europe and Asia, that travel with humans as ship stowaways.
In fact, they have now become established on about 90 percent of the world's major islands and island chains.
It has been observed that these rodents attack bird nesting colonies, eating eggs, chicks, and sometimes even adult birds.
The situation has worsened to the extent that now, 102 of 328 recognized seabird species are considered threatened or endangered by the World Conservation Union, with predation by invasive species ranking among the top dangers.
"Seabirds are important ecological actors in the oceans and on islands, but 30 percent of all seabirds are at risk of extinction," said study co-author Bernie Tershy of the University of California, Santa Cruz.
"Invasive rats are likely the single largest threat to seabirds," he added.
According to the study, smaller seabird species and those that nest in burrows or rock crevices are particularly at risk.
That group includes storm-petrels, auklets, murrelets, and shearwaters, according to lead author Holly Jones of Yale University in New Haven, Connecticut.
"Rats can have a larger impact on entire seabird populations in species with adults that are small enough to prey on," said Jones.
"Burrow- and crevice-nesting seabirds share the same underground habitat as rats, which makes a predation encounter more likely," she explained.
Many seabird species considered vulnerable to rats have been showing local or global declines for decades and have now reached perilously low numbers, according to the researchers.
"Because most seabirds evolved in the absence of any land-based predators, many have no evolutionary adaptation to avoid predation by rats," said Jones.
In addition to seabirds, invasive rats have caused extinctions of many native land birds, reptiles, frogs, and even plants.
"By consuming fruit, seeds, and flowers, rats can change the structure and composition of forests, and alter the entire ecology of islands."
While rodent eradication projects have been opposed by some animal rights activists, conservationists have said that rat removal is the only way some seabirds and other island species can survive.
In this regards, the new study should help conservation managers in different parts of the world prioritize islands for rat eradication and protect the seabird species most at risk.