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Michael Dunne: A couple of times, I've had the unfortunate experience of slamming into a deer while driving. If it's never happened to you, you're lucky. If it has, you know how frightening and shocking it can be. In a state like Oregon, these car-versus-deer collisions are costly and dangerous for drivers.
A new study points to an unlikely hero in reducing these collisions between people and deer, and it's a hero very few of us want to meet in person: the mountain lion. Today on the show, you'll hear from one of the authors of a scientific study showing that the presence of mountain lions near roadways causes deer to move to safer territory, reducing collisions. It's the story of a big carnivore doing humans a big favor, and it's next on Oregon on the Record.
Justin Suraci is a senior scientist and director of wildlife conservation science with Conservation Science Partners. Justin, thanks so much for coming on and talking with us.
Justin Suraci: Thank you, Michael, for having me.
Dunne: Let's start with this: Explain what Conservation Science Partners does. What do you do?
Suraci: Sure. We're a research-based nonprofit headquartered in Truckee, California, but we have projects across the U.S. and globally at this point. It's a group of ecologists and data scientists. We tend to partner with other nonprofits, government agencies and other players and practitioners in the conservation space to provide the analytical support for whatever wildlife management or conservation policy objectives they're trying to achieve.
Dunne: Okay. I'm familiar with the organization Panthera. Have you worked with them on the project we're going to talk about?
Suraci: Yes, exactly. This long-running puma study on the Olympic Peninsula of Washington is actually Panthera's project. Dr. Mark Elbroch is the lead of this Olympic Peninsula cougar study, or puma study. They've been working with several tribal nations in the region, six Native American and American Indian tribes, studying puma and prey habitat and movement for more than 10 years at this point.
Conservation Science Partners came in more recently, over the last three or four years that Mark and I have been collaborating, to provide some of that analytical support and help them derive useful inference from all the puma collar and wildlife camera trap data they've been collecting in the region.
Dunne: Before we get to the study and its findings, I wanted to ask, and maybe it's too large an area to make general assumptions, but roughly speaking, how healthy is the puma or cougar population in the Pacific Northwest, in Washington and Oregon?
Suraci: That's a great question, and one Mark could probably answer better. I haven't had a chance to talk to him about it, but I think puma populations in western North America, in general, are a little spotty. Pumas have persisted in western North America following European colonization. They were essentially wiped out in the eastern half of the United States following colonization, but they persisted out here. In some places they're doing quite well, and in others, less so.
In California, for instance, there are a lot of pumas, but they were recently listed as a state endangered species because of a lack of genetic connectivity between subpopulations scattered across the state. In Oregon and Washington, I have less of a sense of the overall picture, but the Olympic Peninsula puma population is also thought to be suffering from similar genetic disconnectivity with neighboring populations. So there is some concern about this particular study area.
Dunne: Well, honing in on the Olympic Peninsula, let's talk about this study. When I first heard about it, I found it fascinating. Tell people, at a high level, what the study was and what you found.
Suraci: Sure. I'll take a step back and give you a sense of the broader context this study is embedded in: a desire to look at the Olympic Peninsula as a test case for both the costs and benefits that large carnivores, that predators, can provide to the human communities with which they coexist.
As people continue to expand development into more wildland areas, and as many large carnivores like puma start to recolonize areas of their historic range, there's more and more overlap between people and large carnivores across North America and globally. This idea of humans and predators coexisting on shared landscapes is becoming increasingly important.
We know that coexistence has costs. It's not always positive to live alongside predators, and those costs are well articulated and often part of the conversation around humans and wildlife sharing landscapes: things like people losing livestock to predation, or reduced hunting opportunities if something like a puma is killing the deer and elk that hunters would otherwise want to take.
Those costs are well known. What we wanted to do with this study, and with this broader research program, is look at both the costs and the benefits. The benefits are often more cryptic, less well articulated, and at risk of falling out of the conversation around coexistence.
Dunne: Go ahead.
Suraci: That was the context in which we've been conducting the study we're going to talk about today, as well as some prior work looking at these costs and benefits.
One of the potential benefits flagged in prior work, and in theoretical work, is the potential for large carnivores to reduce wildlife-vehicle collisions. This idea has come up before, in two prior examples. One is a theoretical study looking at what would happen if pumas recolonized the eastern U.S., where they've been absent for 100 to 150 years, to the massive, overabundant white-tailed deer populations there, and what would happen to vehicle collisions. The other is an empirical study in Wisconsin showing that as wolves actively recolonize various counties there, deer-vehicle collisions decline.
That idea has been out there. What we wanted to do in this study area is look at whether predators can have these effects in a place where the predator and prey populations are stable and have been for a long time. In the Wisconsin study, and in the other one, the predator is changing its relationship with deer as it recolonizes areas it used to live in, and that's leading to changes in deer-vehicle collisions. That's great, but are those benefits also occurring in places where people are already living alongside large carnivores, and we just don't know about it?
So the motivation here is to look at whether, in a place with ongoing human and large carnivore coexistence, where pumas are certainly killing and eating deer but not necessarily affecting deer population numbers, we can still see these benefits of coexistence.
Dunne: And what did you find, especially with regard to people driving cars and cars hitting deer? What did you find out?
Suraci: The main takeaway is that if you look at the variation in where pumas are spending their time across the Olympic Peninsula, there are some places where puma activity is high and some where it's low. In places where puma activity is high, we saw up to a 76% reduction in the number of deer-vehicle collisions compared with places where puma activity is low.
Again, we don't think that's necessarily because pumas are actively reducing the number of deer on the peninsula right now. These populations are probably pretty stable at equilibrium. What we think is happening, and what we have evidence for from the camera trap data I mentioned earlier, is that pumas are affecting where and when deer are active, and that's affecting deer's exposure to vehicles.
Where puma activity is high, deer are less likely to spend time in areas of higher road density. They spend their time a little farther from more developed areas, and they're more active during the day than at night. All of that can reduce deer's exposure to roads and vehicles, leading to the reduction in deer-vehicle collisions.
Dunne: That's fascinating. Let me reintroduce you to the audience. We're talking with Justin Suraci. He has a Ph.D. and is senior scientist and director of wildlife conservation science for Conservation Science Partners.
So, simplistically, if I understand what you're explaining: There tends to be a lot of deer around roads, especially in rural areas. But if pumas are there doing what pumas do, which is hunt deer, the deer quickly learn they need to be in a different area, perhaps one less exposed because of roadways. Is that part of it? Is the changed landscape, with a road, making it easier for pumas to hunt their natural prey, so their natural prey is saying, maybe I need to be in more wooded areas to protect myself?
Suraci: We think that's the case. It's a little tricky to get at the exact behavioral drivers when all you have are images from cameras. We don't have collars on the deer themselves, which would be really useful for seeing how they're moving on shorter timescales. But yes, we think what you're describing is exactly what's going on: Where pumas are present, deer are perceiving a higher risk of predation in areas with higher road density or that are a little more fragmented by development.
We think this because we've shown it in prior work in the same Olympic Peninsula system, and other studies have found the same thing. Pumas really like edge habitat when they're hunting, forest edges butting up against more open habitat, like an agricultural field or a roadside clearing next to a forest edge. That kind of terrain is great hunting habitat for pumas because they can hide just inside the forest and attack prey out in the open.
Whether the deer, and for that matter the pumas, in this study are responding to roads specifically isn't entirely clear. But we think deer are responding to these edgier, more fragmented habitats, places like forest carved up by roads, or areas of low-density development or agriculture where forest butts up against more developed land. We think deer are potentially perceiving these as riskier because it's good puma hunting habitat, and when pumas are around, deer move to areas where they feel safer.
Dunne: We're going to take a break. I'm Michael Dunne, host of Oregon on the Record. When we come back, more of our conversation with Justin Suraci of Conservation Science Partners about a new study on the benefits of cougars for humans.
And we're back. I'm Michael Dunne, and you're listening to Oregon on the Record. Let's get back to our conversation with Justin Suraci of Conservation Science Partners about a new study on the benefits of cougars for humans.
Take us through how you conducted this study. You've mentioned the trap cameras. Give us an overview, because I imagine it's pretty complex, isn't it?
Suraci: Analytically, maybe. But in terms of the data, it's essentially a bunch of pictures of deer and pumas.
This is a really interesting and important component of the study. I mentioned Panthera and the puma director at Panthera, Mark Elbroch. He and his team have been working in this landscape for about 10 years now, partnering with biologists from six Native American and American Indian tribes on the peninsula. Each of those tribes has its own camera trap network, a set of remote cameras deployed for wildlife monitoring, and the Panthera team has been coordinating across these organizations to compile all of that information.
They've also put GPS collars on pumas, over 100 of them over that 10-year span, and we have data from 503 camera traps as well as, during the study period, data from 59 GPS-collared pumas.
With the cameras specifically, you're getting detections of deer and pumas as they cross the camera's path. We use modeling approaches that let us look at where deer are most likely to be and when they're most likely to be active in places where pumas are present or absent. So: How are deer selecting their habitat, conditional on whether pumas are around? That's essentially the main analytical approach we used to look at changes in deer spatial and temporal habitat use in the presence or absence of pumas. That's all from the cameras.
Then we got data from the Washington State Department of Transportation on the timing and location of deer-vehicle collisions across the peninsula over the five-year study period. We used that data to make inferences about changes in the likelihood, number and timing of deer-vehicle collisions across this gradient of puma activity, from places where pumas are mostly absent or not active on the peninsula to places where they're very active.
Dunne: Deer and cougars have been running from each other and hunting each other for millennia, and certainly they evolved long before people created roads. In your study, are there inferences made about how human changes to the environment have changed the tactics and strategies of predator and prey?
Suraci: There aren't necessarily inferences made directly in our paper about this. We don't write about how human manipulation of the environment is affecting predator-prey interactions specifically. But that's highly relevant to these results, and it's a really interesting, ongoing area of research in wildlife ecology, because you're exactly right: Predators and prey, this exact predator-prey pair, have been interacting for millennia. But the stage on which their ecological drama is unfolding is heavily influenced by humans.
There's been a lot of work elsewhere, though not in our paper, showing that human manipulation of the landscape, human presence and human disturbance can affect many aspects of predator-prey interactions. For instance, many wildlife species become more nocturnal in the presence of people, because people are typically active during the day. If animals want to avoid humans, they need to be more active at night, and in many cases that actually increases overlap between predators and prey. If both need to be more active at the same time, that increases their interaction.
Changes to the landscape, as we're at least alluding to here, in terms of increased fragmentation and more habitat edges, are also certainly having an impact on how predators and prey interact. So these ecological dramas that have been playing out forever are now playing out in a different context, and the conservation implications of that are huge and varied, and only beginning to be understood.
Dunne: I guess other inferences might be possible here. Obviously, people driving their cars and running into deer can exact a large economic toll, and also a safety toll. What can you infer from your study about the real benefit cougars are providing to the motoring public?
Suraci: Yeah, I think that's the key takeaway. There are obviously wildlife-vehicle collisions on the Olympic Peninsula right now. They're causing damage. We report in the paper that they've resulted in something like $14.7 million worth of damage from deer and elk collisions on the Olympic Peninsula over the last five years.
But the main takeaway, or at least the main inference one can make from this paper, is that those numbers, the number of collisions and the amount of cost, would be substantially higher if pumas were absent from the study system. What we're showing is that society on the Olympic Peninsula is receiving a benefit right now from its coexistence with pumas, counterbalanced against whatever costs it's also experiencing in terms of livestock loss and so on. Right now, where pumas are more active, they're reducing wildlife-vehicle collisions, and you could make a pretty clear inference that the number of collisions would be substantially higher in a counterfactual scenario where no pumas are present on the peninsula.
That's actually a next step we want to take with this research. We've made some efforts in this direction, but the next major approach is getting the actual economic value, the dollar amounts, associated with the costs of coexisting with pumas, again, livestock losses being one, and the benefits: how much, in economic terms, human communities on the peninsula are benefiting from the presence of pumas because of things like reduced vehicle collisions.
When you pull all that together, the various costs and benefits, the hope is that we can get a spatially explicit map of the relative cost and benefit these large carnivores are providing to human communities, which will vary in space and depending on who you are. If you have a bunch of sheep in a rural area, you're probably experiencing costs and benefits a little differently than somebody living in a more urbanized area, whose main concern is hitting a deer on the road. That's part of the next step, for sure.
Dunne: Well, go ahead and talk about some of those other benefits.
Suraci: Sure. I think this study fits nicely within a growing body of literature, or growing awareness, of the benefits that large carnivores, or predatory wildlife in general, can bring to people. Reduced wildlife-vehicle collisions might be one. Reduced conflict with other herbivores is a potential benefit, too. If you have pumas present and they're reducing the number of deer or changing deer's space use, you have fewer impacts of deer on agricultural crops, for instance, or on regenerating forests.
Another interesting one that comes up sometimes is the potential benefit of large carnivores in pest management or disease control. There's a really cool example from several years ago in Mumbai, India, where leopards living in and around the city are eating feral dogs and reducing rabies transmission across the human population.
There are all these cryptic benefits that large carnivores could be providing to human societies, and the relative cost and benefit in any particular area, the total net value of living alongside large carnivores, is completely an open question at this point in most geographies and most cases. But I think it's really important that we're starting to identify these benefits, because if we don't, as I mentioned earlier, they fall out of the conversation, and we're only talking about the risks without talking about the rewards of living alongside large carnivores.
Dunne: Fascinating stuff. He is Justin Suraci from Conservation Science Partners. Justin, thank you so much for joining us.
Suraci: My pleasure, Michael. Thanks very much for having me and for your interest in this work.
Dunne: That's the show for today. All episodes of Oregon on the Record are available as a podcast at klcc.org. All next week, we'll focus each day on a nonprofit that might fly under the radar but is making a big difference in the community. Monday's show will focus on a coastal nonprofit that is helping stand up other organizations in the region. I'm Michael Dunne, host of Oregon on the Record. Thanks for listening.
