When a Cape buffalo goes down in South Africa, lions, hyenas, and painted dogs will soon arrive to fight over the carcass.
Using scent detectors on their antennae, dung beetles home in on a pile or feces and descend a lot. Each beetle then races to tear off a chunk, roll it away, bury it, and devour the droppings before the other dung beetles can steal it for their own. But how they are able to navigate away from the fray, and do so in efficient, straight lines, has been the topic of intense study.
In 2003, a scientist by the name of Marie Dacke discovered that nocturnal dung beetle species like Scarabaeus zambesianus can navigate by the polarized light of the moon. A decade later, Dacke found that another species, Scarabaeus satyrus uses the light of the Milky Way when the moon is not available. Scarabaeus lamarcki And now Dacke has discovered yet another tool in the same dung beetle's sensory array. 1
The findings suggest that the animals can interpret two different kinds of signals and opt to use one or the other depending on the conditions around them.
"These systems appear to be extremely flexible," Dacke says. "What is fascinating when you imagine that their brain is about the size of a sesame seed." Beetles battle for a prized ball of dung
Watch two dung beetles fight over a ball of dung — a valuable resource they use both as food and as a nursery for beetle babies. Read more about the fight here
Against the wind
To figure out how dung beetles navigate without their sun compass, Dacke and her colleagues had to first control for variables.
They started by constructing two-foot- wide domes that mimicked the beetles' natural habitat. Next they performed a series of experiments where an adjustable LED stood in for the sun, and fans created different speeds and directions of wind flow. This allowed the scientists to measure the dung beetles' performances under a variety of conditions and show that when the artificial sun was at high noon, the beetles chose to roll their balls into the wind – even when it shifted.
will follow the wind, because that is now the cue that they are using, ”says Dacke, who is an expert in neuroethology, or the study of how the nervous system controls behavior. “If we change the direction of the wind at 180 degrees, the change will change its direction at 180 degrees as well.”
But things really got interesting when the team prevented the beetles from accessing some of their sensory systems. ] In one experiment, the scientists removed the club at the end of the insect's antennae, which is thought to help them sense odors. Like the others, these beetles could be followed by the wind when the sun was high. This suggests that the beetles were feeling the wind rather than smelling something in it. Beetles that had their entire antennae removed, however, rolled their dung balls each and every way, as if lost. The animals could not sense the wind and were rudderless as a result.
Inside the mind of a beetle
Paul Graham, who studies the navigation of the University of Sussex in the United Kingdom, says the study's findings are perfectly clear
"One of the most beautiful rolling rolling systems is that the behavior is easy to interpret, so consistently rolling direction shows us clearly that the bees are using the wind as a directional signal," Graham says in an email
What's more, it's important to be able to understand two different kinds of information — one mechanical, the other visual — into a single brain region. Graham says this suggests "even small-brained animals are sensory processing that is reminiscent of some people would call cognition."
Next up, the dung beetle researchers plan to investigate how a dung beetle evaluates the information provided by either wind or sun and how it determines which one to use.
"We're going to record recordings from the neurons themselves, inside the compass of the beetle," Dacke says.
After more than 15 years of studying these seemingly simple insects and the way they pass the world, plenty of mystery still remains.