The bat family [Emballonuridae], also called sac-winged bats, have bag-shaped glands in each wing that are open to the air. During courtship, males wave their wings in front of the females for a few seconds, dispersing the scent that comes out of these bags.

[...] The team discovered each animal emits an intense odor that broadcasts the chemical composition of what is known as their major histocompatibility complex, or MHC, genotype.

— Read more at Bats Use Body Odor to Sniff Out the Best Mates at Scientific American.

“Using a waste product for a scent marking signal is energetically smart,” she said. “It is costly for animals to create specialized scent secretions, but urine and dung require no extra energy costs. Dung is larger and therefore easier to find, but the longevity of dung vs. urine is species-specific.”

Plenty of other animals, both plant- and meat-eaters, use such communal pooping grounds – and identifying the telltale compounds in their dung could open a new door to studying them as well as to creating new tools for land management and species conservation.

— Courtney Marneweck of the University of KwaZulu-Natal in South Africa, talking about how white rhinos communicate with each other via their dung. Read more at Scientists discover that white rhino dung has a lot in common with a Facebook post at the Los Angeles Times.

Certain features of the orchid-specific brain pattern were recreated when mosquitoes were exposed to body odor. They also found that mosquitoes would actively fly upwind and land on the odor source when exposed to orchid or body odor scents. These results provide strong evidence that orchids use a particular bouquet that shares features with blood-hosts to attract the mosquitoes they rely on for pollination.

— Read more at Orchids mimic human body odor to attract mosquitoes at Phys.org.

But the more esoteric smells—orange, banana, vanilla, and cinnamon—were hits, too, even though wild sea lions are unlikely to find themselves in situations that smell quite so Christmasy. Particular sea lions even picked favorites. “One individual, Sage, was crazy about cinnamon. Just absolutely crazy about it,” says Samuelson.

— Dr. Mystera Samuelson of the Institute for Marine Mammal Studies in Gulfport, Mississippi talks about aromatherapy for sea lions in rehabilitation. Read more at Sea Lions Are Surprisingly Receptive to Holiday Spices at Atlas Obscura.