Mega Grazers

Being female can be a risky business, especially for a Marula tree in Africa receiving the attention of elephants. Marula has separate male and female trees, and the fruiting females rely on the heavyweights of the animal kingdom--African elephants--to spread their fruits. Browsing elephants are far from dainty and can cause mega damage to the trees.

Åsa Hemborg and his colleagues examined the trees in Hluhluwe-Umfolozi Park, KwaZulu Natal, South Africa to put the predilection into evolutionary perspective. "Many fleshy fruits that we enjoy, like mangoes and avocados, once evolved to be eaten and dispersed by elephant-like creatures that are now extinct." Hemborg said. The Marula trees attract elephants from long distances, sending them on a lengthy walk to reach the sweet fruits.

They found that the female trees are at a higher risk than male trees of destruction by the elephants. "There is a conflict of interest experienced by female trees when the disperser also has the potential to seriously damage or kill the tree," Hemborg said. The female trees, however, have not garnered tougher branches, as their branch resistance was similar to that of male trees. Instead, the selective pressure of browsing may promote the evolution of trees a stellar ability to re-sprout, the scientists suggest in a report of their research published in the African Journal of Ecology.

-- LiveScience Staff

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Credit: HIP Game Park, Zululand, KwaZulu Natel