If you’ve ever been forcibly farted on by an older brother or rerouted your walk to avoid a smelly alley or subway station, you understand the power of odor. Skunks and a number of other animals can use their stench defensively, and many use tantalizing aromas to draw in a mate. However, lemurs may be the first ones to use perfume as a weapon. Researchers say male ring-tailed lemurs mix their own potent fragrances from glandular secretions and wield them in “stink fights” with other males. The report is published in the journal Royal Society Open Science.

You wouldn’t guess it to look at them, but the ring-tailed lemur (Lemur catta) and other lemurs are primates like humans. But unlike humans, L. catta is endangered and increasingly concentrated in shrinking small forest habitats on the island of Madagascar. They’re highly social animals, living in big groups of up to 30 animals. Consequently, getting along—or at least avoiding all-out brawls—is pretty important. So instead of resorting to violence, male lemurs joust with custom-blended body odor.

Each male lemur has dedicated ingredient glands on his chest (brachial, or B gland) and on the inside of his wrist (antebrachial, or A gland). The A gland produces a clear liquid, while the B gland makes a nasty-smelling brown paste.

Brachial (L) and antebrachial (R) glands. Image credit: Alex Dunkel via Wikimedia Commons // CC BY 3.0

These secretions can be used alone, as when the lemurs rub their wrists against trees to mark their territory, or in combination, either via wrist rubbing or through what researchers have termed “stink fighting.” Contenders rub the liquid on their wrists into the brown mash on their chests, then smear the resulting blend onto the tips of their tails. They then hoist their tails into the air and wave them around, aggressively fanning their stench at their opponents.

Observing this behavior, researchers at the Duke Lemur Center wondered why the lemurs would mix their fragrances, rather than just using secretions straight from the source. They rounded up 12 of the center’s lemurs and swabbed both sets of glands to collect secretions. Next, they smeared each lemur’s secretions on three wooden dowels: one with just gland A fluid, one with just gland B paste, and one with a mixture. The researchers brought the lemurs back in and gave them the chance to check out scented dowels from a male they didn’t know. Each lemur was offered two rounds: first, dowels with fresh secretions, and then those that had been sitting around for 12 hours, allowing the scent to evaporate.

When every lemur had had his smell test, the researchers analyzed the behavior patterns associated with each dowel. They found that, as expected, the lemurs were more interested in the blended fragrance. But they also learned that their test subjects were even more captivated by older scents, moving from sniffing to straight-up licking the other males’ dried-out secretions.

The scientists say the blended scents may be constructed like human perfumes, with each note (in this case, type of secretion) providing different information. They also think that mixing helps the fragrance stick around. On its own, A-gland fluid evaporates pretty quickly. But the paste produced by B glands includes a chemical called squalene, which is actually used in human perfume as a fixative, to keep a scent active longer. This could allow scent marking to serve like a flag, allowing a male to stake a claim and walk away.