'Niche market' for W Cape dung beetles

2013-10-21 21:53

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Cape Town – Western Cape residents have a reputation for being different to their up-country cousins, and so too, it seems, do the region’s dung beetles.

According to a University of the Witwatersrand researcher, three species of West Coast dung beetles, all members of the genus Pachysoma, have given up flying and taken to “galloping”.

Such behaviour is really odd, Professor Marcus Byrne said in a statement on Monday.

“Most insects walk with a tripod gait. They plant three legs in a triangle, while swinging the other three legs forward. It’s an incredibly stable way of walking because you’ve always got three legs on the ground.

“For an insect to abandon the tripod gait and use its legs together in pairs like a galloping horse is really radical. The big question is: why are they doing it?”

Byrne said the three beetle species – Pachysoma glentoni, Pachysoma hippocrates and Pachysoma endroedyi – had not only changed the way they moved across land, but also lost their ability to fly.

“There are 800 species of dung beetle in South Africa and most of them fly. To fly makes sense, because pooh is a very ephemeral resource. It’s only useful for a few days and it’s very patchy. You don’t know where you’re going to find the next dropping.

“That’s why Pachysoma is so weird. Why would anyone give up flying?” Byrne and his colleagues think the beetles may have done so to conserve moisture in the harsh semi-desert environment in which they live.

They may have changed the way they walk to help navigate their way through the West Coast sand.

“For most dung beetles, it’s always a one way trip – grab the pooh, run away and never go back. The very marked pacing of Pachysoma’s gallop might be giving it a better signal in terms of estimating the return distance from the food to its nest.”

According to Byrne: “The unique behaviour of this galloping, flightless species has allowed it to dominate a niche market among dung collectors of the Western Cape.”

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