Discoveries

August 03, 2023

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It’s not as uncommon as one might think to see animals and birds getting drunk after eating too much fruit.

After all, ethanol occurs naturally in fruit as a product of fermentation by wild yeast.

Few studies, however, have explored how alcohol influences the relationship between plants and animals. Now, a new paper suggested it plays a big role in seed dispersal, New Scientist reported.

Researcher Julia Casorso and her team collected more than 70 plant species in a Costa Rican tropical dry forest and measured the alcohol concentration produced by each fruit.

They sorted the fruit based on what animals eat: They labeled small, brightly colored fruit as bird-dispersed, heavier, duller fruit as mammal-dispersed, and soft, succulent fruit as mixed-dispersal. They analyzed 37 species after removing fruit with small sample sizes.

Their analysis showed noticeable alcohol levels in 78 percent of the fruit species and that those with higher ethanol content were more likely to be dispersed by mammals.

The team explained that mammals are enticed by the alcohol because it alludes to a ripe and sugary snack that provides more nutrition.

“Mammals in particular use their sense of smell to find food,” said Casorso. “Ethanol is one odor amongst the many aromas that fruit produces and the fruit might be using alcohol to attract dispersers.”

Meanwhile, the yeast benefit: this animal-plant interaction causes the fauna to disperse wild yeast spores.

This story originally appeared in the August 03, 2023 newsletter, Dimming Star.