"Insects are well known for being able to perform amazing feats of strength," explained Knell, "and it's all on account of their curious sex lives. Female beetles of this species dig tunnels under a dung pat, where males mate with them. If a male enters a tunnel that is already occupied by a rival, they fight by locking horns and try to push each other out."
The scientists tested the beetle's ability to resist rivals by measuring how much weight was needed to pull a male beetle out of his hole.
"Interestingly, some male dung beetles don't fight over females," said Knell. "They are smaller, weaker and don't have horns like the larger males. Even when we fed them up they didn't grow stronger, so we know it's not because they have a poorer diet."
He added, "They did, however, develop substantially bigger testicles for their body size. This suggests they sneak behind the back of the other male, waiting until he's looking the other way for a chance to mate with the female. Instead of growing super strength to fight for a female, they grow lots more sperm to increase their chances of fertilizing her eggs and fathering the next generation."