Reincarnation, Dung Beetles, and the Southern Milky Way

I’ve always been unsettled by the idea of reincarnation. While I’m at the top of the food chain now, I have a suspicion that, with my many karmic transgressions, I may not be so lucky next time around. After I die, what if I come back as a swamp rat? Or a garden slug? Or worse yet… a dung beetle? It’s not an appealing thought.

Well it turns out dung beetles, at least, might have more going for them than I thought. A new study by Swedish biologist suggests that a species of South African dung beetle navigates on moonless nights with the help of the spectacular southern Milky Way.

There are 6,000 species of dung beetles, but they all make their living in the same way. The beetles thrive on the feces of large animals such as cows, tigers, and bison, slicing up their mountainous prize into little pieces they each use to nurture the next generation. A male dung beetle carves off a piece from the larger pile and rolls it away by pushing backward with his front legs while controlling his ball of dung with his back legs. He then finds a good spot and buries the ball. If he successfully attracts a female, she will lay a single egg in the little dung ball. Once hatched, the larva slowly eats through the ball and arrives into the world.

To avoid larger robber beetles, a smart male dung beetle must take his little treasure and bury it without delay, which means he needs to navigate a straight line. Daytime beetles use the Sun, specifically, the polarization of the Sun’s light to help find their way. Nighttime species use the Moon, but as most stargazers know, the Moon is not always present in the night sky. The Swedish biologists suspected the eyes of the beetles are too small to accurately detect bright stars. But could they see the bright band of the Milky Way?

Image credit: Tunç Tezel

The southern Milky Way (image credit: Tunç Tezel)

So the Swedish team collaborated with South African biologists to test their idea. The Milky Way is much brighter in the southern hemisphere than in the north, and it extends across the entire sky. From a site on the edge of the Kalahari desert, the researchers ran a group of controlled experiments with a species of nocturnal dung beetle wherein they blocked the beetles’ view of the horizon, and alternately blocked and unblocked their view of the starry sky on a moonless night.

It turns out that the beetles push their piles much faster when they could see the night sky. To refine the test, the team moved the beetles to a planetarium where the contents of the “sky” could be controlled. When the beetles saw only the 18 brightest stars, they got lost. When the bright stars were blocked by the planetarium projector and the only the southern Milky Way revealed, the beetles found their way again, clearly proving the Milky Way was the means of navigation for these industrious little creatures.

Biologists suspect other insects such as crickets and bees might also use the Milky Way to navigate on moonless nights.

By all accounts, dung beetles are noble creatures. They perform a useful function. They are tenacious and single-minded. And it turns out they are pretty good stargazers too.

And when you think about it, on a cosmic scale, we’re not much bigger than a dung beetle, and likely not much further along the evolutionary scale. And we share the same view of the stars. Maybe reincarnation isn’t so scary after all.