Goats repay trees with a good seed spit

Tree-climbing goats in Morocco pay their way by giving their roosts where they feed a boost. They spit the trees’ seeds on the ground.

Herders in the arid southern part of Morocco even encourage their domesticated goats to climb by pruning the thorny argan trees the animals love, reports Live Science. Especially in autumn, when other vegetation is scarce, the fruit of the argan tree is an important source of calories for the goats.

The goats may be important for the trees as well. Researchers have now found climbing goats consume the olive-like fruit of the argan tree and later spit out the nuts, according to a report in the journal Frontiers in Ecology and the Environment. Other cud-chewing ruminant animals might do the same, the researchers wrote, meaning that regurgitation could be just as important as defecation for spreading some seeds.

Study authors Miguel Delibes, Irene Castañeda and José M. Fedriani of the Doñana Biological Station in Seville, Spain, had previously seen goats in dry areas of Mexico and Spain climbing on short bushes and trees to graze. The goats in Morocco, though, tower above the competition – 10 to 20 at a time were regularly seen climbing argan trees between 8m and 10m.

Plenty of argan seeds could be observed amid the spit-out cud and faeces after the goats moved through, but it was impossible to tell whether the goats were regurgitating or defecating the seeds. Argan seeds are large, up to 22mm wide, so it seemed unlikely they were moving through the entire digestive tract, the researchers wrote.

To show regurgitation was the likely culprit, the researchers fed goats five different fruits with different size seeds. Almost any seed of any size could be spit out during rumination, or cud chewing, they found, but larger seeds were more frequently expectorated than smaller ones. Further testing found 71 per cent of ruminated, spat-out seeds were still viable.

The authors also reported seeing red deer and fallow deer as well as sheep spitting seeds while ruminating, suggesting this behaviour might be important for seed dispersal.

Ruminants can keep their cud tucked away in their rumen, or first stomach, for days at a time, the researchers wrote, so a goat being herded long distances or making a seasonal migration could transport seeds for hundreds of kilometres.

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