How animals use the stars

The animal world is intricately entwined with the night sky. Naturalist Megan Shersby looks at some fascinating ways that animals take their cues from the cosmos

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Humans have long marvelled at the night sky above us, inspired by the Moon and the stars to invent stories and myths, travel the oceans and learn more about the Universe in which we live. At the same time, animals have also been using celestial cues to orient themselves. From tiny foraging ants and dung-rolling beetles using moonlight, to birds navigating their migration by the stars, a wide variety of species rely on the night sky to thrive and survive.

Sea turtles

Both the female turtles that lay their eggs on their natal beach and the hatchlings that emerge a few weeks later head towards the brightest horizon to enter the ocean, where the water reflects the light of the Moon - avoiding the darker landward silhouettes. However, artificial lights from urban developments disorient them and they can end up circling the beach in confusion or worse, head towards our roads and buildings - sometimes with fatal consequences.

Moths

It's well known that many moth species will fly towards a candle, lamp or other light source - a behaviour called positive phototaxis - and it's been theorised that this is because they are mistaking it for a celestial cue that they would use for orientation.

A recent study using three-dimensional flight data suggests that nocturnal moths turn their back on the brightest light - historically the Moon and the sky - and this would tell them which way was up. With the introduction of other, human-made sources of illumination, the insects become trapped in a loop, sometimes flying upside down and occasionally causing an insect to crash. The scientists suggest that the moths are not attracted to artificial lights but trapped by them, similar to being caught in a net.

Bats