Nature may abhor a vacuum, but she certainly rewards a liar. Wild cheaters abound in the plant and animal kingdoms, from the tippy-top of the food chain to the very bottom. The newest addition to the rogues gallery is Ceratocaryum argenteum, a South African plant that quite literally looks like crap.
Scientists found that C. argenteum’s seeds are so convincingly poop-like that dung beetles will make off with them and bury them in the dirt. The large, round seeds not only look like the dung of local antelopes—they also smell like it, which is how they can trick dung beetles into planting them.
Poop is, unsurprisingly, the center of the dung beetle’s universe. Food, drink, a place to raise the kids, and sometimes even home are rolled into one smelly ball. As such, dung beetles can be a little single-minded, which makes them a prime target for tricksters and scammers. Burrowing owls, for example, casually strew balls of dung outside their dens, then gobble up any beetles that come sniffing around.
In a paper published this week in Nature Plants, researchers from the University of South Africa and University of KwaZulu-Natal analyzed the stink emanating from C. argenteum seeds. They found that a number of the seeds' smelly compounds matched those in antelope poop precisely.
To find out if the seeds’ odor actually appealed to dung beetles, the scientists scattered 195 C. argenteum seeds in areas of heavy dung beetle traffic. They set up motion-capture cameras at each site and attached fluorescent threads to each seed to make it easy to spot if a beetle carried it off. Sure enough, within 24 hours, dung beetles had absconded with and buried more than one quarter of the reeking seeds. The stench also seemed to deter animals that might eat the seeds without burying them.
Once buried, the C. argenteum seeds sprout and start a whole new generation of smelly, lying plants. Burial keeps the seeds safe from any chaos on the surface, which is a big deal in the fire-prone shrublands where they make their home.
It’s a pretty neat trick, but how did the plants come up with it? Lead author Jeremy Midgley suspects a combination of dumb luck and chemical evolution.
“I guess that a mutant individual, which had some chemical on the seed coat, attracted the odd beetle and the seed was buried," Midgley said in an interview with Discovery News. "This plant then did very well because fewer seeds were discovered and eaten by small mammals, and that fires damaged fewer of the buried seeds."
Meanwhile, the beetles who did the heavy lifting in this particular experiment were left looking pretty silly. At least they weren't forced to wear tiny cardboard hats.