Call it “love at first sniff.” In animals and humans, scent plays a bigger role in romance than you might think.

Take the Coquerel’s sifaka, a type of lemur. New research published in the journal Animal Behavior shows that two sifakas start mimicking the other’s scent-marking behavior early on in courtship.

"It's like singing a duet, but with smells instead of sounds," Duke University scientist Christine Drea, co-author of the lemur study, said in a statement.

Sifaka couples that had babies together also smell more like each other than couples without kids. Drea and her colleagues think this might happen because the lemurs are exchanging odor-producing bacteria through their domestic rituals: mating, grooming, and other kinds of contact. The daily routine of being a couple weds the lemur partners’ individual scents into one.

But lemurs aren’t the only creatures that bond through scent. Humans, despite our nasal shortcomings -- some scientists argue we’re actually relatively decent smellers, but we’re still leagues behind cats, dogs and other critters – can still perk up at telltale smells, even if we don’t always know it.

We may be sending one another scent messages all the time, in unexpected ways. Israeli researchers performed an experiment where women watched a sad movie scene, and collected the resulting tears. When they wafted the sad-tainted tears under the noses of some male subjects, the response wasn’t, as they expected, a surge in empathy, but a decline in testosterone levels and sexual arousal.

And pair bonds may increase our sensitivity to a partner’s scent. Researchers collected sweat from volunteers to capture their body odor while they were in a neutral mood, or in a variety of heightened states – fear, happiness or arousal. Then they gave the sweat samples to another person – either a stranger to the first subject, or a romantic partner. Though participants couldn’t distinguish between specific emotions conveyed through sweat, they could distinguish between neutral and moody odors – and the romantic partners were able to do it better than strangers, with those in the longest-term relationships performing the best.

But the power of scent doesn’t mean that you can use it as an instant shortcut to romance -- yet.

“There’s really nothing that you can spray on and the opposite sex will fall for you,” Johan Lundstrom, an assistant member of the Monell Chemical Senses Center in Philadelphia, told the New York Times in 2011. “It’s completely a placebo effect.”

That hasn’t stopped fragrance makers from touting perfumes designed to lure the opposite sex. Harvey Prince, for example, sells a fragrance with notes of pumpkin pie, lavender and jasmine – supposedly a recipe for attracting men. For the gents, there’s colognes spiked with “pheromones” that sellers claim will turn the ladies’ heads.

But humans "use all sorts of cues” in selecting a partner, Columbia University biologist Stuart Firestein told ABC News. “A pheromone alone is unlikely to do it. It's part of a whole package.”

Depending on the situation, your synthetic scent may attract a partner you weren’t expecting. Zookeepers and biologists have discovered that tigers, cheetahs, jaguars and other big cats go wild for the smell of Calvin Klein’s Obsession for Men. ­­In one Bronx Zoo experiment, cheetahs stuck around sniffing Obsession-sprayed objects for more than 11 minutes – longer than they usually linger over a meal, according to the Wall Street Journal.

Obsession is "a combination of this lickable vanilla heart married to this fresh green top note — it creates tension," fragrance designer Ann Gottlieb, who created the Calvin Klein scent, told the WSJ in 2010. But the key kitty-attracting component may be a synthetic replica of the musk produced by the cat-like civet.

"It sparks curiosity with humans and, apparently, animals,” Gottlieb said.

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