There comes a time in a dunghill’s life when the only hope of overcoming an obstacle without losing their precious ball is a partner who can pull off a decent headstand.
When their path is blocked, pairs of dung beetles carefully coordinate their actions, with males grabbing the dung ball from above, and females going into a headstand to push the ball off the ground with their legs, researchers say.
The unusual cooperative behavior between spider dung sweepers is believed to be a unique example of animals other than humans working together to move objects around without knowing their final destination.
As ants coordinate to haul food to their nests, and social spiders work together to carry prey to their shelters, both know where they are going and when they have arrived. With dung beetles, couples start rolling their dung balls with no idea where they will stop.
“This is the first species recorded to be able to coordinate transport in this way,” said Dr Claudia Tocco, who studies animal behavior at Lund University in Sweden. “They don’t know where they are going, but they can still coordinate to move the object together.”
Tocco investigated South African spider dung pickers in the hope of finding out what mating accomplished. In other species of dung beetles that roll balls in pairs, females get a ride by clinging to balls of dung, or follow their ball-rolling male.
She gave dung beetles access to cow dung and compared how well single dung beetles and mating pairs rolled the balls when obstacles of different heights blocked their path. The particular species lives in forests and faces constant obstructions in the form of plants and rocks. They bury the balls for food or to lay eggs in.
The researcher found that male beetles always took the role of dung ball hauler, grabbing the ball with their front legs while walking backwards. Females always helped from behind and walked backwards with their hind legs on the ball.
On flat ground, pairs of beetles did not roll faster than single males, but when faced with obstacles, the pairs shot ahead. When challenged by walls up to 9 cm long, males began to climb and drag the ball up, as females worked themselves into a headstand and pushed with their legs to help the ball off the ground. The females then held onto the ball while the male pulled it up – lifting about 10 times his body weight.
Sometimes males clung to walls with just one claw, and females repeatedly saved them from falling when they lost their grip, the scientists wrote in Proceedings of the Royal Society B. Pairs of beetles were faster than singles and more efficient over obstacles, which would be “extremely beneficial” in the forest, the authors noted.
But while pairing makes sense, how the beetles coordinate their actions remains a mystery. “How does a beetle with a brain smaller than a grain of rice communicate? And how do they coordinate with each other in carrying out this task?” Tocco said. “They don’t know where they are going.”
