How do you invent a better way of finding small, secretive, inconspicuous animals like bats? Hint: it involves hanging bags of poop in trees.

While some bat species form hard-to-miss colonies that number in the thousands, others prefer to roost in tree hollows with just a few of their kind, making them much harder to track down. And yet knowing where these species like to hang out can be key to protecting their preferred habitat.

The problem? The main method of finding these bat roosts – capturing the bats, fitting them with radio trackers and then following them home – is expensive for researchers and stressful for the animals.

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Rare Allen's lappet-browed bats (Idionycteris phyllotis) roosting in Arizona. Image: Michael Durham

That's why Northern Arizona University researcher Carol Chambers and her team decided to look for a better alternative – and they found one in the furry form of a scent-detecting dog. These canine "conservationists" had already been unleashed elsewhere in the country to sniff out lynx, pregnant polar bears and even whales.

Chambers and a colleague first set off from Arizona to Washington to work with a company that specialises in training detector dogs. “Each dog was different – it was like working with different people,” she recalls. “They’re fun animals, but they have a very strong drive.”

Two of the canines travelled back to northern Arizona with the team, and spent a week getting used to the region's mountainous forests before the real work started. To test the dogs’ skills at locating bat roosts in a natural environment, Chambers wanted them to home in on one particular smell: bat poop.

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CJ, a chocolate lab, is a trained wildlife detector dog. Image: Michael Durham

"I think poop’s pretty cool,” says Chambers. “Bat guano is actually dry – these are insectivorous bats – but it does have a scent, some bats more than others."

Where bats regularly hang out, poop piles up – follow its scent and you find the bats. To test the dogs' ability to do just that, the team hung bags of guano in trees across their study site. "We got pounds of this stuff, and we ended up ordering some of those pretty little organza sachet bags because we needed something somewhat porous to hold the guano," Chambers explains. "So there we were, sitting around the kitchen table and [bagging] guano." 

The poop-sniffing canines didn't disappoint. When the bags were hung two meters above the ground, the dogs were able to find them 60 to 80 percent of the time (accuracy dropped when the bags were higher up). The success rate with actual bat roosts was a little lower, but even when the dogs couldn’t pick out precise locations, they often identified roosting areas to within about thirty metres.

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CJ enthusiastically sniffs out roosting sites. Image: Michael Durham

While the dogs in this study were trained using a mix of guano from different bat species, canine noses are sensitive enough that they could easily be taught to focus on individual species of conservation interest.

Chambers hopes, for example, that dogs could help land managers identify bats' favourite forest hangouts, so these spots could be preserved during logging or development. With bat species facing a growing number of threats – including a fungal disease that has killed millions of the animals across North America – such protection measures are more important now than ever. 

“People tend to be afraid of bats. They tend to think they’re creepy and ugly and gross, but I don’t think that way at all,” Chambers says. And now, thanks to some hard-working dogs and organza sachets full of poop, conservationists may have another tool for protecting these underrated creatures.