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These tree-climbing goats disperse seeds by spitting instead of pooping them out, study says

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The seeds are used to make argan oil, used in expensive beauty products

Goats graze on an argan tree in southwestern Morocco.
Photo by H Garrido / EBD-CSIC

In Morocco, goats help disperse the seeds of local argan trees by spitting them out. This way of disseminating seeds might actually be more common than scientists have previously thought, according to a new study.

First off, let’s talk about the Moroccan goats. Because these aren’t your normal, pasture-grazing goats. These animals climb on top of trees that measure 26 to 33 feet high to graze. That’s because southwestern Morocco, where the argan tree grows, doesn’t get a lot of rain — so sometimes, the only food the goats can find is on top of evergreen shrubs and trees. In the fall, these tree-climbing goats devote more than 70 percent of their eating time to “treetop grazing.” (This over-harvesting can actually hurt the trees.)

Let’s talk about the argan trees, because these aren’t your normal, pretty trees, either. Their seeds are used to produce argan oil — which is the most expensive edible oil in the world and is included in luxurious beauty products. The tree-climbing goats love the pulpy fruit of the argan tree, but there’s some debate about how they get rid of its seeds. The study published this month in the journal Frontiers in Ecology and the Environment wanted to set the record straight.

In some arid habitats, such as argan forests, most green vegetation is on the tops of trees and goats climb there to feed.
Photo by J Román / EBD-CSIC

Popular accounts — reported in various news outlets — say that locals feed the argan fruits to the goats so that the animals can get rid of the pulp for them. Then, the seeds are collected from the goats’ poop to make the precious oil. However, the authors of today’s study say, goats don’t usually poop large seeds. (The argan seed, at about 0.86 inches in length and 0.6 inches in width, is considered large.) So the researchers began wondering: what if the goats aren’t pooping the seeds, but spitting them out? (The regurgitated seeds and feces “are usually mixed, resulting in misunderstandings about the way the nuts were expelled,” the study says.)

Goats are ruminants, meaning they re-chew their food after leaving it in a specialized stomach to ferment. Goats in Spain have been observed spitting the seeds of olive trees and dwarf palms while re-chewing their food. So why not the Moroccan goats?

To find out, the researchers fed domestic goats fruits of different sizes from five plant species. The goats spat out seeds from each species, and did so more frequently when the seeds were larger. More than 70 percent of the discarded seeds were still viable, the study says. That means that when the goats spit out the argan seeds as they go about their day, they help the tree disperse its seeds far away from the mother plant.

This type of seed dispersal isn’t limited to goats, the study says. The authors say that they have observed other ruminants like sheep and deer do this as well in southern Spain. And, they suggest, it might be more common than we thought.

As for the tree-climbing goats of Morocco and the argan trees, if you use beauty products with argan oil, I hope you’re not grossed out about the goat spit. It’s better than poop anyway, right?