Anyone who has picnicked on the beach has experienced the unpleasant crunch of a sandwich with a surprise helping of sand. But for primates, the tolerance for sand may depend on whether their energy is better spent reproducing and fighting rivals or on protecting their teeth from a mouthful of grit, according to a new Dartmouth study.

Social rank may determine whether animals prioritize immediate energy consumption over long-term health, or vice versa, the researchers report in the journal eLife. They observed the eating habits of long-tailed macaques on Thailand’s Koram Island and found that the dominant and lowest-ranked animals briefly rubbed sand-covered food on their fur or between their paws before devouring it, along with most of the sand, and moving on to the next morsel.

Middle-ranked monkeys, however, having more time on their paws, carried their food to the water’s edge and washed it in the sea to remove the sand. These animals often expended time and energy scrubbing their snacks past the point when they were clean and would even amble down the beach on their hind legs with their front paws full of food.