Nocturnal animals can use the stars and the Milky Way to find their way during the darkest hours, according to a new review article, published in the Proceedings of the Royal Society B.
African dung beetles (Scarabaeus satyrus) use the glow of the Milky Way to navigate. Image credit: Emily Baird.
In their article, Lund University biologist Dr. James Foster and co-authors assess the stars as a ‘visual stimulus that conveys directional information.’
They also compare the bodies of evidence available for the ‘different stellar orientation strategies’ proposed to date.
“There are advantages to being active in the night,” the scientists said.
“Fewer parasites are active and the same goes for predators. What is more, there are not as many competitors for food as there are during the day.”
“For animals that migrate or search for food over vast distances in particular, the cooler hours of the night are preferable to the heat of the Sun.”
“A key requirement for nocturnal animals is that they can hold their course in the dark,” they noted.
“Migrating birds that take off at sunset rely on their magnetic compass, but also the star compass when they use individual stars for orientation.”
“Dung beetles do not use individual stars. Instead, they travel through the night with the help of the light from the Milky Way, which contrasts to the surrounding dark sky.”
Studies also show that seals, moths, frogs and other animals use the starry sky to navigate at night.
“Animals with camera eyes, the type of eyes that we humans possess, can discern individual stars,” Dr. Foster said.
“Insects with compound eyes most likely cannot, but we believe that they can interpret the starry sky and the Milky Way as patterns of light.”
“We still know very little about how nocturnal animals experience and interpret the night sky,” he said.
“For example, no one has yet determined whether, and how, migrating birds change their point of reference in the night sky when they pass the equator.”
“We propose that new sky imaging technologies, combined with more explicit statements of the predicted features of different stellar orientation strategies, will allow star compasses to be discovered, confirmed and characterized in more species, and help to answer fundamental questions of how animals guide their darkest journeys,” the researchers said.
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James J. Foster et al. 2018. How animals follow the stars. Proc. R. Soc. B 285 (1871): 20172322; doi: 10.1098/rspb.2017.2322
