Tree-climbing goats disperse seeds by spitting

Typography

In dry southern Morocco, domesticated goats climb to the precarious tippy tops of native argan trees to find fresh forage. Local herders occasionally prune the bushy, thorny trees for easier climbing and even help goat kids learn to climb. During the bare autumn season, goats spend three quarters of their foraging time “treetop grazing.”

Spanish ecologists have observed an unusual way in which the goats may be benefiting the trees: the goats spit the trees’ seeds. Miguel Delibes, Irene Castañeda, and José M Fedriani reported their discovery in the latest Natural History Note in the May issue of the Ecological Society of America’s journal Frontiers in Ecology and the Environment. The paper is open access.

In dry southern Morocco, domesticated goats climb to the precarious tippy tops of native argan trees to find fresh forage. Local herders occasionally prune the bushy, thorny trees for easier climbing and even help goat kids learn to climb. During the bare autumn season, goats spend three quarters of their foraging time “treetop grazing.”

Spanish ecologists have observed an unusual way in which the goats may be benefiting the trees: the goats spit the trees’ seeds. Miguel Delibes, Irene Castañeda, and José M Fedriani reported their discovery in the latest Natural History Note in the May issue of the Ecological Society of America’s journal Frontiers in Ecology and the Environment. The paper is open access.

Argan may be familiar from popular beauty products that feature argan oil, made from the tree’s nuts. The nut is surrounded by a pulpy fruit that looks a bit like a giant green olive. For goats, the fruits are a tasty treat worth climbing up to 30 feet into the branches to obtain.

But the goats don’t like the large seeds. Like cows, sheep, and deer, goats re-chew their food after fermenting it for a while in a specialized stomach. While ruminating over their cud, the goats spit out the argan nuts, delivering clean seeds to new ground, wherever the goat has wandered. Gaining some distance from the parent tree gives the seedling a better chance of survival.

Read more at Ecological Society of America

Image: Goats graze on an argan tree in southwestern Morocco. In the fruiting season, many clean argan nuts are spat out by the goats while chewing their cud. (Credit: H Garrido / EBD-CSIC)