According to research, a plague of house mice is devastating the Californian Farallon island ecosystem.
Tiny rodents feed on native insects, seabirds, and plants found nowhere else. The results of the study were published in PeerJ – Life and the environment diary.
Mice were introduced to the Farallon Islands, 30 miles from San Francisco, by nineteenth-century sailors. Their population has since grown to around 50,000, covering an area roughly the size of two soccer fields.
Currently, the US Fish and Wildlife Service is proposing a plan to eliminate them.
Lead author Professor Michael Polito of Louisiana State University said: “Before this study, there was a lack of data on what exactly the mice ate on the island and how their diet changed over the course of the year.”
Professor Polito’s team used a technique called stable isotope analysis to trace the chemical signatures of food in mouse tissue.
He explained: “In effect, the mice are what they eat.”
They also examined their seasonal abundance over 17 years – relating it to the availability of native seabirds, salamanders, insects, and vegetation.
The study found that mice are highly “omnivorous and opportunistic” individuals whose numbers and diets vary dramatically throughout the year due to availability and climate.
In spring, they eat mostly plants. With the advent of summer, their numbers begin to increase and they begin to rely more on native insects and seabirds.
By the fall, the community is booming. The density can be as high as 1,200 mice per acre – the highest of any island in the world.
Professor Polito said: “The native plants and many animals cannot leave the island to escape the mice. These plants and wild animals never needed to develop a defensive behavior against rodents as land-based species do. ‘
The question of how to best solve the growing problem sparked a decade-long conservation crisis.
Recently, federal authorities proposed a controversial solution to drop a poison on a rodent called brodifacoum from helicopters.
Critics have argued that it could harm marine life and could even cause an epidemic of dead seagulls in nearby San Francisco.
Co-author Pete Warzybok, Farallon Islands program manager at Point Blue Conservation Science, said: “Our study provides the latest and most comprehensive understanding of the mouse diet and its impact on the native community – particularly the endemic arboreal salamander.”
“Sometimes you’ll see the ground move as mice dig their little tunnels underneath them. The numbers are really amazing. “
Almost all of the world’s 10,000 stormy shearls live off the coast of California – half on the island. Owls attracted by mice eat one or two petrels for the night.
It illustrates the perfect balance in nature as humans bring uninvited visitors to fragile ecosystems around the world.
Produced in collaboration with SWNS Talker.
This story was reported to Newsweek via Zenger news.
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