動物行動学：蛾の航行は星空に導かれている

The Australian Bogong moth may be the first invertebrate known to be able to use the stars to navigate, a paper in Nature suggests. Experiments in flight simulators indicate that the insects use stellar cues, in addition to a magnetic sense, to help them fly in the right direction. Star-based navigation has previously only been observed in some birds and humans, and possibly seals.

Each spring, billions of nocturnal Bogong moths (Agrotis infusa) escape the heat of southeast Australia by migrating up to 1,000 km to cool caves in the Australian Alps — a place they have never previously visited. Here, they lie dormant until autumn, when they make a return migration to their breeding grounds to reproduce and die. Previous research has shown that the insects sense the Earth’s magnetic field, and it is thought that this sense, together with the use of visual landmarks, helps them to reach their chosen destination. However, what visual features the moths use to navigate have been unclear.

Eric Warrant and colleagues show that Bogong moths can use the starry sky as a compass to discern direction. The authors capture moths at the start of their spring or autumn migrations and place them in a flight simulator that resembles a planetarium (recreating natural night skies) with the Earth’s magnetic field blocked. They show that the captured moths fly in their seasonally appropriate direction. In addition, the researchers show that visual neurons in the moth’s brain responded specifically to rotations of the night sky and were tuned to a common sky orientation, firing maximally as the moth headed southwards.

The exact features of the night sky that aid moth migration are still unclear; whether individual stars can be seen by the moth’s compound eye remains uncertain. However, the Milky Way is a bright strip of light in the southern half of the sky that is most likely visible to Bogong moths, the authors suggest.