Do you know what happens when rodents reach critical mass on small islands? They begin eating nesting seabirds alive.

Sometimes multiple rats or mice will attack a helpless chick, sometimes a single rodent will return to a nest for several days until the chick finally dies. The more dense the rodent population, the more aggressive they become. Protective adult birds will tenaciously continue incubating their eggs even as mice chew away their flesh, and mice will attack birds as large as petrels and albatrosses.

Consider Gough Island in the south Atlantic, one of Earth’s most important seabird nesting islands. Over the past decade introduced mice have eaten a staggering 1.8 million birds annually on Gough—in only a few years, some species have suffered population crashes so severe that they are now critically endangered, highly vulnerable to other human introduced threats in the oceans. My very close cousins, the Tristan Albatrosses, are among the most endangered. As soon as the Covid-19 epidemic allows work to begin, the Royal Society for Protection of Birds will begin dropping cereal pellets containing rodenticide on Gough, with the goal of fully eradicating the mice by 2022. A drastic solution, but the problem is truly catastrophic.

Photos from the Royal Society for the Protection of Birds.