A golden retriever in Eugene is helping unearth Oregon’s truffle biodiversity

In Europe, dogs have been used for centuries for their keen sense of smell to locate prized black and white truffles, which can fetch hundreds or thousands of dollars a pound depending on their variety.

In Oregon and the Pacific Northwest, using dogs to sniff out truffles is relatively new and growing in popularity. There are even training classes and an annual truffle dog contest held at the Oregon Truffle Festival.

Related: How the Oregon truffle bends humans to its will

Oregon has four varieties of gourmet edible truffles, but there are hundreds of species of these mysterious fungi growing on the roots of conifer and oak trees across the state.

So what if you could use a dog’s nose to home in on the odor signatures of all sorts of truffles, not just the commercially valuable ones, for a better scientific understanding of truffle biodiversity?

That’s the goal of Heather Dawson, a doctoral student in the biology department at the University of Oregon. She trained her golden retriever, Rye, to detect dozens of different kinds of truffles in the Willamette Valley alone.

She joins us to share her work and the attention it’s attracting among other scientists and forest foragers.

Note: The following transcript was transcribed digitally and validated for accuracy, readability and formatting by an OPB volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. Dogs have been used in Europe for centuries to locate prized black and white truffles, which can fetch hundreds or even thousands of dollars a pound. In Oregon, using dogs to sniff out truffles is relatively new, but it is growing in popularity. In general, dogs are trained to find edible truffles, but there are plenty of other species of these fungi growing underground. Heather Dawson wants to find those as well. Dawson is a doctoral student in the biology department at the University of Oregon. She trained her golden retriever, Rye, to detect dozens of different kinds of truffles in the Willamette Valley alone, and she joins us now. It’s great to have you on Think Out Loud.

Heather Dawson: Hi, Dave. Thanks so much for having me.

Miller: What is a truffle?

Dawson: In simple terms, we can basically think of a truffle as an underground mushroom. Most fungi that we see in the forest produce these aboveground fruiting bodies, so to speak, in order to spread their spores. Truffles are doing exactly the same thing. They have these spores that they use to reproduce, but instead of fruiting above ground, they fruit below ground. And that actually offers a lot of protection from the elements such as drought, heat stress, cold stress – because the soil acts as an insulative situation for them to be in. So, it’s pretty unique, but it’s also incredibly widespread across a lot of different fungal lineages.

Miller: I guess you’ve just described why it is that they’re hard to find … because they’re underground. You can’t look for the telltale yellowish-orangish chanterelle mushroom. They’re underground.

Dawson: Exactly, and that means that when you’re out walking through the forest, whether you’re just there for a hike or if you’re actually out mushroom picking, you are probably walking all over truffles. And you have no idea because they’re beneath your feet, they’re hidden away.

Miller: How did you first get interested in truffles?

Dawson: I pretty much got interested through my first dog. I moved to Oregon a decade ago. I was young and I was really excited. I got my first dog and I wanted to do fun training things with her. And that’s when I learned that Oregon had two species of native culinary truffles: the Oregon white truffle and the Oregon black truffle. That was the extent of my truffle knowledge at the time, but I thought, how cool. What a fun activity to do with your dog. So I decided to train her. It was definitely a process, but it was exciting.

Miller: How do you train a dog to find truffles?

Dawson: The simplest way to do it is just find something that the dog really, really likes. Then pair that with the truffle aroma. It’s basically conditioning your dog to associate the smell of truffles with something that they find really exciting, whether that’s a really good treat like liver treats or hot dogs. My current dog Rye, being a ball-crazy golden retriever, I figured out pretty quickly that he will want his ball to find a truffle, instead of food.

Miller: Have you had any dogs who actually like to eat truffles?

Dawson: Yes, unfortunately, that’s actually a common issue that people have when they’re training their dogs to find the truffles, because dogs actually think they smell pretty good sometimes, too. My first dog was perfect, she never even considered eating truffles. Rye will sometimes take a nibble of the Oregon black truffle, because it smells really sweet and quite pleasant to dogs. And my newest dog, Pyro, he’s still kind of a puppy at this point, he really went all in on the truffle appreciation side of things. He’s got a few different groups of truffles that he really enjoys. And sometimes I have to race him to those truffles, otherwise he gobbles them down before I get there.

Miller: So in the past, if the idea was to find these truffles – either because people really love them themselves to eat, or to sell them as moneymakers – did that mean that the dogs weren’t being trained or rewarded for finding other truffles?

Dawson: Exactly. For most people, when they go out in the forest looking for truffles, any truffle that doesn’t match the description of something culinary is just not interesting, because you can’t eat it, you can’t sell it – it’s basically just worthless if you’re a truffle harvester, so to speak.

I think most people, when they are looking for truffles, do encounter these other species. And dogs often experiment with finding truffles with different aromas. But if they’re not rewarded for finding those species, then they’re going to stop finding those species, which is usually what the truffle harvesters have in mind. For me, I went the complete opposite direction and thought, well, culinary truffles are fun, but what other surprises are hiding under the surface there?

Miller: Oh, so you do the opposite. If they find a white or black one at this point – the standard culinary truffles – they don’t get a ball?

Dawson: I usually do reward them. I tend to amp up my rewards a little bit if it’s something new and exciting, to really encourage them to diversify to different aromas. I usually reward them for the culinary ones as well just because they get a reward for pretty much every single truffle they find. But now and then it’s not as big a reward as something that I’m truly excited about.

Miller: What does it look like when you go out with your golden retriever, Rye, who seems to be your current truffling star?

Dawson: I take him out both in a formal survey context when I’m doing studies at my research sites here in Eugene, but also just when I go for a hike and have fun in the forest. He always has his truffle nose on. Basically, I just let him run loose and he has certain cues that I use to tell him we’re looking for truffles. I’ll say, “Rye, find a truffle,” or, “Find it.” Sometimes all I have to do is show him his ball and he’s like, OK, I’m on it. I’m on the job.

He basically just runs around. He does some level of air scenting and ground scenting to catch that truffle scent. And it’s pretty neat to watch him getting close, because he’ll kind of triangulate it and circle around. And it’s quite obvious. Once he’s found the truffle scent, he stops and his tail starts wildly wagging because he’s anticipating that ball reward. He’s like, this truffle smells like the ball that I’m about to get. So, his tail is wagging and then he starts pawing at the ground. Sometimes it’s a big truffle and it just pops right out. I’ll be like, “Good boy, Rye, you can get your ball.”

But often these things are really small, really hard to see … of course, to him it’s a really strong odor, but he has to take the time to hunt around in that little pile of soil that he’s dug up to find this teeny tiny truffle because otherwise I’m gonna have no hope in finding it.

Miller: How small a truffle has he found and how buried have they been? I guess I’m just wondering how acute his sense of smell is, in terms of his ability to find tiny bits of these aromatic fungi.

Dawson: I am constantly amazed. As far as the smallest goes, pinhead-sized, absolutely. I mean, it’ll take me a long time to see what he’s pointing at. He’ll point at it with his nose and I’m like, Rye, I do not see anything. And then he keeps doing that because, of course, he’s not wrong. He knows where it is. I’ll pick it up and it’s literally the tiniest pebble-sized piece of dirt-looking-thing you can imagine. But then I’ll smell it or cut it in half and be like, OK, that’s a truffle.

But even beyond that, sometimes he finds truffles that, to me, don’t have any odor. But to him, he’s able to pick something up because, being a dog, he has this incredible sense of smell that humans can never fully imagine. And on top of that, the depth that he can smell a truffle is also quite incredible. Most truffles you find pretty much between this mineral soil layer and the organic surface layer on top. That’s usually where truffles hang out, but not all the time, especially in cold areas, often snowmount areas, he’ll dig down easily over a foot deep to find a truffle.

Miller: I can imagine, as you are looking for that pinhead-sized truffle and wondering if indeed it’s there, him just thinking, “Listen, human, just give me the ball now because I know it’s there. You’ll find it eventually, but just give me the ball while you keep looking for the truffle, because I found this thing …”

Dawson: Really impatient sometimes.

Miller: What is at stake in this? To go back to the “why,” here – as you noted, people have been finding white and black truffles for a long time, versions native to Oregon and others in Europe. And probably inadvertently along the way, their dogs or pigs before that have been alerting to other truffles that the humans have said, “No, ignore that.” But what do you most want to find?

Dawson: Really, I just want to find the diversity that’s out there. Truffles remain one of the most understudied groups of fungi, simply because they do fruit underground and they’re hard to find. But they’re doing really important things in the ecosystem, and there are so many undescribed species out there. There’s so many species that we’ve only found a handful of times or in just one area. And we don’t know the true extent of where they are and whether they need protecting or not.

There are certain forests that are at greater risk than others, certain habitats, ecosystems. And we know comparatively little about the fungi in these ecosystems, especially compared to plants and animals. So my main goal is figuring out really what’s out there, what do we need to protect? And that’s going to be the first step in truly understanding what all these different species are doing, because with a level of biodiversity that high, they are all doing important and unique things in these ecosystems.

Miller: What are the places where you’ve had the most success in finding the greatest number of different truffle species?

Dawson: It’s really all over the place. Honestly, most of my work is in oak savanna here in the Willamette Valley, but also in southern Oregon. I’ve explored a little bit in California as well. Oak savanna is really fascinating. These habitats have quite a lot of truffles compared to above ground mushrooms. Primarily, the thinking is, because they dry out quite readily, especially during the summer, but also, they simply don’t have this protective moisture layer, organic layer, so to speak, that you find in a conifer forest. And that has really driven the evolution of truffles many times over these different lineages because of that dry habitat.

So, I find some pretty incredible diversity in oak savanna, but that is not to say there’s not also incredible diversity out in conifer forests. I like to hike in the summers at high elevation. And of course, because I’m out there hiking with my dogs, I’m constantly seeing what kind of truffles exist in this habitat too. It is pretty fascinating. I can’t pinpoint one particular location that has extraordinarily higher diversity compared to others. A lot of times it’s just site-specific. I’ll just come across one little patch and find a whole bunch of different species right there.

Miller: How is climate change affecting truffles?

Dawson: That’s a great question and one that we don’t necessarily know a lot about, because we don’t know that much about truffles. We don’t even know that much about how fungi are responding to climate change. One of the big things that I’m concerned about is the megafires that are getting more frequent, especially in the Cascade Range here in Oregon and Washington.

Most truffle species are ectomycorrhizal, which means they associate with the roots of host trees and they actually can’t survive without their tree hosts. And when these fires come through and kill large numbers of trees, you’re also killing many of the fungi that live on those roots. So, we’re going to end up losing a lot of things that we potentially didn’t even know were there and may not be able to save in the future.

Miller: When your [dogs] find, whether it’s a pinhead size truffle or a larger one, and you get it, how do you catalog them?

Dawson: It’s pretty fun. I hike around with my little truffle knife and my camera. It’s really important to get good pictures, so I try to cut it in half to show the full characteristics of the truffle. I’ll take notes on the tree species in the area, what the truffle smells like, take pictures of the habitat. And ultimately, what I’m really excited about is, I do a lot of DNA sequencing of the truffles I find.

Truffles are incredibly hard to tell apart at the species level without looking closer, either at the spores, but also at their molecular biology. So I take a little, teeny, tiny sample of the fresh truffle and then I’m able to do this DNA barcoding on it, essentially, to tell it apart from other species that I found. And that’s been incredibly informative in showing just how high the truffle biodiversity is in Oregon and also how many of these are undescribed or new species.

Miller: Heather Dawson, thanks so much.

Dawson: Thank you.

Miller: Heather Dawson is a doctoral student at the University of Oregon who has trained her dogs to find non-edible varieties of truffles.

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