Today it is difficult for us to imagine a long sea voyage without requiring satellite navigation systems, such as GPS. Before the arrival of the digital age , our ancestors crossed the oceans using a method much more linked to observing nature, astronomical navigation . A millenary science, and at the same time an art, which consisted in orienting oneself by looking at the stars , in reading the sky to know its position and direction on the high seas.
However, millions of years before the appearance of the human being , multiple species of nocturnal animals already looked to the stars to guide themselves and adapt their behaviors and life cycles . An example would be the beetles players who use the stars to guide them at night while carrying their dung balls, as discovered in South Africa more than ten years ago researchers Marie Dacke and Eric Warrant of the University of Lund.
In their observations, they watched as the beetles gathered around the manure piles and carefully chose each portion to create balls larger than themselves. When finished, they climbed onto their creation and looked up at the sky. By having compound eyes, instead of dots in the sky, it could be said that they saw the stars as spots, something that was very useful for them to differentiate the line that the Milky Way creates, essential to orient themselves and roll their ball in a line almost perfect straight.
A decade later, the now Dr. Dacke, remains convinced that many animals orient themselves by looking at the stars. During this time, he has continued to study South African dung beetles. However, today something has changed. According to their latest study publishing in the journal Current Biology , beetles that live near cities are becoming disoriented due to light pollution.
Despite this fact, the beetles have not remained cross-legged in the face of the threat. According to the new work of Dr. Drake, these beetles have been forced to resort to a beacon strategy , that is, to rely on beacons or bright signals that they find on their way at ground level. This change in behavior could result in an attraction towards artificial lights, increasing competition between individuals and reducing their dispersion efficiency.
Unsurprisingly, dung beetles aren’t the only ones affected by light pollution . During the migrations of spotted seals, beach fleas, moths and numerous migratory birds, among many other species, being able to see the sky is essential.
For this reason, the authors of the study, in an interview for The New York Times , conclude “ we propose that future efforts to mitigate the impact of light pollution focus not only on preserving darkness at night from a human perspective, but also also in minimizing the disturbance of the compass signals on which many nocturnal species depend ” .
References:
Foster, J. J., Tocco, C., Smolka, J., Khaldy, L., Baird, E., Byrne, M. J., Nilsson, D. E., & Dacke, M. (2021). Light pollution forces a change in dung beetle orientation behavior. Current Biology, 31(17), 3935–3942.e3. https://doi.org/10.1016/j.cub.2021.06.038
