The unappreciated dung, or scarab beetle, an insect that evolved about 130 million years ago, must accomplish its nocturnal task under increasingly difficult conditions; chief among them, light pollution.
Colorado hosts over 85 species of dung beetles, a subset of the approximately 9,800 species worldwide.
Male dung beetles roll dung balls to entice a female to mate and impress her with a fecal feast for her future progeny. She lays an egg in the ball and adult beetles emerge, ready to feed, mate, and roll new dung balls, completing the cycle.
These nocturnal beetles rely on celestial navigation. The Milky Way’s wide, bright linear path across the sky provides a reliable directional reference for their navigation. Furthermore, scientists have discovered that dung beetles are the only known creature, so far, that can detect the angle of polarization of moonlight to refine their paths. This dual system allows precise navigation, critical for efficient dung transport across the beetles’ ecosystem.
Light pollution, particularly blue-rich LEDs, masks these critical beetle navigation aids causing disorientation. A 2019 study found that light pollution reduces the dung beetle’s foraging efficiency, increases energy expenditure, and disrupts reproduction, as the beetles are drawn to artificial lights.
Why is this nocturnal activity of dung beetles important instead of just a curious fact? Because dung beetles are important to ecosystem health. They aerate the soil, increase nutrient uptake, reduce carbon emissions, reduce insect pests, and disperse seeds encased in the dung. Ecosystem scientists use dung beetle population as an indicator of ecosystem health. So, this small insect, unknown to many, rolling balls of dung around at night guided by the Milky Way and moon is important to us as one of those ecosystem inhabitants.
We have disturbed their ability to help ecosystems by our indiscriminate use of light. We can reduce that light pollution disturbance by using Smart Lighting principles:
- only use light where and when it is needed,
- lower intensity to safe eye levels, very bright lights blind you
- use warm colors not blue, and
- put a shade on it to direct light down where it is wanted, not up or sideways.
Dung beetles depend on dark skies to navigate and thrive. Their celestial dance with the Milky Way and moon reminds us that preserving starlit nights protects not just these remarkable insects but helps our ecosystems. By controlling artificial light at night, we can ensure that dung beetles keep rolling under the Rockies, sustaining soils and skies alike.