For hundreds of years humans have been using bright stars and stars patterns to navigate the high seas and find their way home on land. But it turns out that many other Earth inhabitants can read the ‚Äúmap‚ÄĚ of the night sky too! From tiny beetles to birds and giant whales, these are the animals that follow the stars!
Dung beetle astronomers
Dung beetles are supermen of the animal world. They can pull dung balls tens and hundreds times their own body weight. Moreover, dung beetles roll the poo-balls away from the dung pile in more or less straight lines (in other words, in the fastest way possible). This is crucial for their survival as the competition near a dung pile is (APPARENTLY) fierce. To stay on a straight course the super beetles use the light of the Sun. But what about the beetles that work at night?
In 2009 a group of scientists led by the Swedish biologist Marie Dacke studied Scarabaeus Satyrus, the nocturnal African dung beetle, that, too, can roll in a straight line. At first, scientists thought that the beetles used the light of the Moon to navigate, but, to their surprise, even on moonless nights, with only stars in the sky, Scarabaeus Satyrus kept a straight-line orientation. Did these nocturnal beetles follow the stars? To test the theory, biologists observed the beetles and recorded their movements under various sky conditions. Scientists even got some beetles to wear cardboard hats that prevented them from seeing the stars! At the end of the experiment biologists concluded that clever little dung beetles learned to follow the Milky Way (which is much more prominent in the Southern Hemisphere), rather than individual stars, to keep the straight-line orientation.¬†You can read the original publication¬†here.¬†
Some migratory birds fly only during the day, others fly at night. But how do the night flyers navigate over the vast distances, in the dark, often through rain and wind, and never get lost? Can they possibly use stars for navigation?
About 40 years ago prof. Stephen T. Emlen of Cornell University decided to find out!
He raised several groups of Indigo Buntings, migratory birds native to North America, in a planetarium. One group could see the sky that rotated around the North star (the same sky you and I see every night). Another group lived under the altered sky that rotated around the star Betelgeuse.¬†In the Autumn both groups were tested under the “normal” planetarium sky. What do you think happened? The first group oriented themselves away from the North Star, ready to migrate South. But the second group oriented themselves away from Betelgeuse, as if it was the North Star.
Dr Emlen concluded that birds indeed use stars for navigation, but not in a way we humans do. Birds observe the rotation of the sky to find Polaris (where the movement of the stars is the slowest) and determine the North-South orientation. Clever!¬†You will find the original publication here.
Marine animal stargazers
Humpback whales make the longest journeys of all migrating mammals. They spend summer time near the poles and return to the tropics in the winter, covering 5 000- 8 000 miles of an open ocean per trip.The studies show that these animals navigate across the sea in nearly perfect straight lines with a deviation of 1 degree or less despite the weather, currents and variations in the depth of the ocean. (You can read about the study by Travis Horton¬†here ). Scientists think that humpbacks use several aids to stay on such precise course: the Sun, the Moon, the Earth magnetic field and, yes, the stars!¬†
Another study hints that seals might be skilled star navigators too.
While, obviously, more research is needed to confirm the theory, we find the idea that marine animals, just like humans, use stars for navigation, absolutely fascinating!