January 24, 2013
Dung Beetles Use Milky Way For Nocturnal Navigation
Lee Rannals for redOrbit.com — Your Universe Online
Back before technology emerged into everyone's pockets, sailors used the stars as their GPS system when navigating the seven seas. While that way of navigation is a little outdated for humans, it´s still a modern technology for dung beetles.
Researchers say that this discovery is the first convincing evidence for insects using the night sky to help guide them. It is also the first example of any animals using the Milky Way as their GPS, rather than the stars.
"Even on clear, moonless nights, many dung beetles still manage to orientate along straight paths," said Marie Dacke of Lund University in Sweden. "This led us to suspect that the beetles exploit the starry sky for orientation–a feat that had, to our knowledge, never before been demonstrated in an insect."
Scientists found that the African ball-rolling insects transport their dung balls along straight paths under a starlit sky, but lose the ability under overcast conditions. In a planetarium, the beetles were able to stay on track equally well under a full starlit sky, as well as one showing only the streak of the Milky Way.
They said that the insects use the Milky Way because the night sky is littered with stars, but the vast majority of those stars are too dim for the beetles' eyes to see.
The latest findings raise the possibility that other nocturnal insects may also be using the stars to help guide themselves around at night. While no other insects have been found, yet, to guide themselves by way of stars, it is not too surprising that the intelligent insects are able to use nature's navigator as their source of path at night.
"Dung beetles are known to use celestial compass cues such as the sun, the moon, and the pattern of polarized light formed around these light sources to roll their balls of dung along straight paths," Dacke said. "Celestial compass cues dominate straight-line orientation in dung beetles so strongly that, to our knowledge, this is the only animal with a visual compass system that ignores the extra orientation precision that landmarks can offer."
The team believes the beetles have a hierarchy of preference when it comes to available light sources. So, if the moon and the Milky Way are visible at the same time, the beetles use one rather than the other.
When the beetles climb on top of their dung balls, the researchers say the insects perform an orientation "dance" to locate light sources for orientation.
(Left Image Below) Image Caption: You might expect dung beetles to keep their “noses to the ground,” but they are actually incredibly attuned to the sky. A report published online on Jan. 24 in Current Biology, a Cell Press publication, shows that even on the darkest of nights, African ball-rolling insects are guided by the soft glow of the Milky Way. Credit: Current Biology, Dacke et al.
(Right Image Below) Image Caption: Researchers gave dung beetles caps to block out light. Credit: Marcus Byrne