In the African savanna, fresh dung is a coveted prize sought by thousands of competitors within minutes. To protect its prize, the nocturnal dung beetle (Scarabaeus satyrus) needs to move away from the original pile as fast as possible and in a perfectly straight line, avoiding curves that would lead it back into the danger of fights.
During the day, these beetles use the Sun and atmospheric polarization patterns to maintain a fixed course, and during clear nights they rely on moonlight. However, their most surprising secret comes to light on pitch-black, moonless nights: they are the first animals on the planet proven to use the Milky Way to plot their navigation.
The finding was made by an international team led by biologist Marie Dacke from Lund University. By conducting experiments in the Johannesburg planetarium and out in the savanna, the researchers discovered fascinating details about the insect's behavior:
- Galactic contrast: The beetle's compound eyes lack the resolution needed to distinguish individual stars, but they are highly sensitive to broad gradients of light; they clearly detect the whitish, diffuse band of the galaxy crossing the sky.
- The 'cap' experiment: When beetles were fitted with tiny black cardboard caps that blocked their view of the sky, they immediately lost their ability to orient themselves, tracing erratic loops without moving forward.
- Dome navigation: When only the overhead projection of the Milky Way was turned on inside the planetarium, the beetles instantly resumed straight, efficient paths.
This sophisticated celestial compass shows that even the humblest creatures turn to the vastness of the cosmos to ensure their daily survival.
Source: Current Biology (Dacke et al., 2013 - 'Dung Beetles Use the Milky Way for Orientation')
