13 October 2015

Plant fools dung beetles

Ceratocaryum argenteum, a rush-like flowering plant native to South Africa... produces large, round nuts that are strikingly similar in appearance, smell, and chemical composition to antelope droppings (in particular those of the eland and the bontebok), which the dung beetles accordingly roll away and bury, effectively sowing a new generation of C. argenteum. Although scientists have observed dung beetles providing similar services elsewhere in the plant kingdom—as, for example, when the dung happens to contain fruit seeds—this is the first known case of a dung beetle helping and not ending up with any dung.

Jeremy Midgley, the lead author of the study, which was published on Monday, in the journal Nature Plants, first became interested in Ceratocaryum nuts because of their large size. This quality, he originally hypothesized, might make them attractive to rodents. From the beginning, he told me, the nuts’ distinctive smell was “very apparent and was confusing,” but he thought there was a chance that other animals might not find it off-putting. Using motion-sensitive cameras, Midgley and his colleagues recorded two hundred and fourteen instances of mice interacting with the nuts. In this footage, he said, the general mouse attitude appeared to be “either disinterested or even repelled.” But, by triggering the cameras, the mice revealed something that the biologists might otherwise never have noticed: dung beetles industriously rolling the nuts away. Suddenly, Midgley said, “the color, shape, size, and smell made sense.” The scientists revised their experiment, setting out a large number of Ceratocaryum nuts after the rain (a time favored by dung beetles) and equipping them with fluorescent thread markers that enabled them to be tracked with a special flashlight. Of the sixty-six nuts that were successfully recovered, fifty-three had been buried, beetle-style.
Further details at the The New Yorker.


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