Study: Mongoose release in Amami isle made frogs more skittish
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AMAMI, Kagoshima Prefecture–Frogs on Amami-Oshima island developed a quicker flight reaction to predators after mongooses were brought into their ecosystem, a study showed.
The alien species not only preyed on domestic animals and reduced their numbers but also affected their behavior, according to researchers from the Tokyo University of Agriculture and Technology, the National Institute for Environmental Studies and other parties.
The small Indian mongoose was brought to the island to reduce the population of venomous “habu” snakes in 1979. But the mongooses also attacked Amami rabbits and other endangered animals, prompting the Environment Ministry to take measures to eradicate the mongooses in 2000.
The mongooses are currently on the brink of eradication on the island.
In 2013, Hirotaka Komine, a specially appointed assistant professor at the university who specializes in ecology, and other researchers studied how the mongooses affected the Amami rabbit. They also measured the “flight initiation distance” (FID) of 278 frogs found on forest roads in several areas of the island.
The FID is an index used to measure the distance at which an animal starts to flee from an approaching human.
In an area 24 kilometers from the point where the mongooses were released, the frogs started to flee when humans were within 1.43 meters on average.
But in an area just 10 km from the mongoose release point, the frogs fled when humans were 3.23 meters away.
The study showed that the frogs reacted sooner to potential danger in areas where the mongooses had a stronger influence, the researchers said.
The frogs were also quick to flee in areas where the mongooses had been nearly eradicated in 2013, when the study was conducted.
“Although the mongooses are gone, the changes in the frog’s behavior will not be reversed anytime soon,” Komine said.
He added that the introduction of alien species could have affected the behavior of other domestic species.
The findings were published in the Zoological Society of London’s specialized magazine, Journal of Zoology, in autumn.
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