In The Gutter But Looking At The Stars: Dung Beetles Use the Night Sky to Navigate

Another article from Animalia, which made the print newspaper too! Unfortunately credit for the excellent title goes to my editor rather than me. Today's post features the first insects shown to use the stars for navigation.

Dacke et al. (2013) Current Biology

Many animals are known to orient themselves according to the Sun, and some even to the Moon, but the dung, or scarab, beetle, has become the first known insect to also use the stars.

Once dung beetles find a good dung heap they roll their ball away in a straight line, to avoid coming full circle straight back to it, but this means that heading off in the right direction to begin with is very important. If they get it wrong, they could also bump into another beetle that might steal their dung.

Scarabaeus satyrus still managed to navigate away from potential thieves on clear nights with no moon. Trying to work out what other indicators the beetles might be using, they carried out experiments in the field by attaching pieces of cardboard to the beetles to impede their vision (shown in the picture above). When placed in an arena with a dung ball in the middle, the shielded beetles took far longer to reach the edge than the control beetles, which had clear caps.

In the first experiment, the beetles might have been able to use other landmarks, like trees, as visual cues, so a second experiment was designed so that the beetles could only see the sky. The time taken for the beetles to reach the edge of the arena on moonless nights was not significantly more than on nights with a full moon. Beetles with cardboard caps, however, took much longer to navigate, as did all beetles on an overcast night.

A further experiment was designed to work out how exactly the beetles used the stars by changing projected lights in a planetarium. Here they found that the beetles could navigate just as well using only the vague glow of the (artificial) Milky Way as when 4000 individual stars were projected. Not only then, are these beetles the first insects to use the stars to navigate, they are now the first ever animals to have been shown to use the Milky Way.

Following the publication of their paper in the journal Current Biology, Dr Dacke says that the team will “continue to look at how the starry sky looks through the eyes of the [dung] beetles… since there are still many things about celestial orientation in beetles that we do not understand.”

#beetles #insects #animalbehaviour