Female dung beetles use horns to fight over manure

Mar 04, 2010 by Lin Edwards report
Dung beetle (Onthophagus sagittarius) Image credit: U.Schmidt.

(PhysOrg.com) -- Dung beetles are among the few species in which the females are more impressively equipped with armor than males, and a new study explains why: the females fight each other for the best manure and breeding sites.

University of Western Australia researchers, Prof. Leigh Simmons and Dr. Nicola Watson, studied the female (Onthophagus sagittarius), which, as its name suggests, feeds on dung. When they arranged for the females to have to race each other to reach deposits of cow dung and access to egg-laying sites in tunnels beneath the dung, those with larger horns were able to gather more manure, and thus provide more of this valuable resource for supporting their young.

In a study published in the , the researchers said competition between females for the use of breeding resources reduced the reproductive fitness of all the beetles, but smaller beetles were worse off than larger individuals. When matched for body size, the longest horns gave the greatest advantage in reproductive fitness, producing significantly more broods than beetles with shorter horns.

Dung beetles lay their eggs in balls of dung, which must be fresh for the beetles to use it and this is what leads to competition. Watson said there is a distinct advantage for females that can get to dung first and seize the best and freshest pieces. They have also been observed stealing dung from other females and replacing eggs with their own.

Dung beetles are also unusual in that the female dung beetles’ horns are of a different type to those of male beetles, and the scientists suggest this means they have evolved independently. Unlike male , they are not used for fighting off predators, defending territory, or competing for mates, but for fighting off other competing with them for resources.

Explore further: Too many chefs: Smaller groups exhibit more accurate decision-making

More information: Reproductive competition promotes the evolution of female weaponry, Nicola L. Watson, Leigh W. Simmons; Proceedings of the Royal Society B. doi:10.1098/rspb.2009.2335

Related Stories

Can't compete on dung? Try mating on apple pomace

Jun 24, 2009

In the mating world of yellow dung flies, large, brawny males almost always get the girl. However, a new study suggests that smaller males rule if presented with an opportunity to woo females when they are not hanging out ...

Armed beetles find a mate, whatever their size

Mar 27, 2008

One species of armed beetle is proving that size doesn’t necessarily matter when it comes to finding a mate. The creature’s ‘pulling techniques’ will be revealed in the April edition of the Royal En ...

Beetle dung helps forests recover from fire

Nov 29, 2007

Armed with a pair of tweezers and a handful of beetle droppings, University of Alberta forestry graduate Tyler Cobb has discovered why the bug-sized dung is so important to areas ravaged by fire.

Recommended for you

Field study shows how sailfish use their bill to catch fish

20 hours ago

(Phys.org) —A large team of European researchers has finally revealed the purpose of the long, thin, needle-like bill sported by the famous sailfish. It's used, they report in their paper published in Proceedings of ...

Explainer: How do homing pigeons navigate?

20 hours ago

Pigeons have extraordinary navigational abilities. Take a pigeon from its loft and let it go somewhere it has never been before and it will, after circling in the sky for while, head home. This remarkable ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

NamelessMaster
not rated yet Mar 04, 2010
That's funny...they use the same technique in the Junior League!
Jeswin
2 / 5 (1) Mar 10, 2010
Wow contradicts this sexual dimorphism in which males usually possess the distinguishing characteristics due to sexual selection via male competition

More news stories

When things get glassy, molecules go fractal

Colorful church windows, beads on a necklace and many of our favorite plastics share something in common—they all belong to a state of matter known as glasses. School children learn the difference between ...

SK Hynix posts Q1 surge in net profit

South Korea's SK Hynix Inc said Thursday its first-quarter net profit surged nearly 350 percent from the previous year on a spike in sales of PC memory chips.