Joel Kontinen
Bogong
moths are the first invertebrates known to navigate using the night sky during
annual migrations to highland caves
Can the Australian moth use the stars to reach a destination that is a thousand kilometres away?
The
answer seems to be Yes, they can. This is according to the latest research.
An
Australian moth that migrates over 1000 kilometres to seek respite from summer
heat is the first known invertebrate to use the stars as a compass on long
journeys.
Every
spring, billions of bogong moths (Agrotis infusa) travel from various
parts of southern Australia to cool caves in the Australian Alps after spending
the winter as caterpillars feeding on vegetation. Once in the caves, they have
a long period of inactivity, called aestivation, before returning to their
breeding grounds.
It has long
been a mystery exactly how these moths, whose numbers have been collapsing in
recent years, navigate so far to these high country caves, says Andrea
Adden at the Francis Crick Institute in London.
Previous
studies have shown that they are able to use Earth’s electromagnetic
field, but only in combination with landmarks they can see. Adden and her
colleagues wanted to find out what other cues the moths may be using to
navigate.
“If you go
to the Australian bush, where these moths live, and look around at night, one
of the most striking visual landmarks is the Milky Way,” she says. “We know
that daytime migratory insects use the sun, so testing the starry sky seemed an
obvious thing to try.”
To do so,
the team caught moths during their migration using light traps and took them to
a lab. There, the insects were placed in a Perspex arena and an image of the
night sky was projected onto a screen above them. The moths were tethered
inside the arena but could pick a flight direction based on the sky image. The
researchers used a device called a Helmholtz coil to essentially cancel out
Earth’s magnetic field.
The tests
showed that the moths use a stellar compass, says team member Eric Warrant at Lund University, Sweden. “When
tethered moths were placed under highly realistic local starry night skies,
they flew in their inherited migratory direction,” he says. “They did this
solely with the help of these stars – all other visual cues, as well as the
Earth’s magnetic field, were absent.”
When the
team turned the starry sky by 180 degrees, moths flew in the opposite
direction, and when they randomly redistributed the natural stars across the
image they were completely disoriented.
In a second
experiment, the moths were fixed in place with a very thin electrode inserted
in their brains. This revealed changes in the moths’ neural activity when
the projected sky image was rotated.
Although dung
beetles use the Milky Way to stay on the same bearing over short
distances, no insect was known to use celestial navigation for migration until
now.
“The bogong
moth is the first invertebrate we know of that is able to use the stars as a
compass for long-distance navigation to a distant destination that it has never
previously been to,” says Warrant. “Only humans and some species of night
migratory birds are known to have this ability.”
Another
insect famous for long-distance migrations, the monarch butterfly (Danaus
plexippus), uses the sun to navigate, factoring in the time of day.
It may be
that intelligent design has given these moths the way to use the start and the
worlds electromagnetic field to do this.
Source:
James Woodford 2025
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