A team of researchers has designed a robot that scares away the invasive mosquitofish, which bites off the tails of freshwater fish and tadpoles to eat their eggs. The new study demonstrates how fear can alter the behavior, physiology, and fertility of the mosquitofish, and it can have big implications in the fight against invasive species.

To fight the invasive fish, the international team, composed of biologists and engineers from Australia, the U.S., and Italy, turned to its natural predator -- the largemouth bass (Micropterus salmoides) -- for inspiration. They crafted a robotic fish that mimics the appearance and simulates the movements of the real predator. Aided by computer vision, the robot strikes when it spots the mosquitofish approaching tadpoles of an Australian species (Litoria moorei), which is threatened by mosquitofish in the wild. Scared and stressed, the mosquitofish showed fearful behaviors and experienced weight loss, changes in body shape, and a reduction in fertility, all of which impair their survival and reproduction. "Mosquitofish is one of the 100 world's worst invasive species, and current methods to eradicate it are too expensive and time-consuming to effectively contrast its spread," says first author Giovanni Polverino (@GioPolverino) of the University of Western Australia.

Robotic fish might help solve an ecological problem by scaring an invasive fish species so profoundly that it is put off breeding. Eastern mosquitofish (Gambusia holbrooki) were introduced in many parts of the world to eat mosquito larvae and keep the disease-spreading insects under control. But they have had a negative and unintended consequence on local fauna: they chew the tails of native freshwater fish and tadpoles, then leave them to die. Reducing numbers of eastern mosquitofish without harming other wildlife is a difficult prospect, but Giovanni Polverino at the University of Western Australia and his colleagues have come up with a potential solution. They designed a robotic version of the largemouth bass (Micropterus salmoides), which naturally preys on mosquitofish.