How roadkill is leading to a harmful problem for Oregon’s Sage Grouse

In Baker County roadkill is creating a problem – not for drivers but Sage Grouse. Carcasses of animals are attracting ravens, and when those scavengers are in the sagebrush area, they prey on Sage Grouse chicks and eggs. We’ll hear from Baker County Implementation Team Sage Grouse Coordinator Dallas Hall Defrees on why this is a growing concern and from Jon Dinkins, assistant professor at Oregon State University’s Animal and Rangeland Sciences department, on the threat from ravens and possible responses to it.

The following transcript was created by a computer and edited by a volunteer:

Dave Miller: This is Think Out Loud on OPB, I’m Dave Miller. We start today in Baker County where people are talking about doing something they haven’t done before. To boost the population of Sage Grouse, they want to get rid of roadkill, which can attract ravens. Those ravens can end up eating Sage Grouse. Dallas Hall Defrees is the Coordinator for Baker County’s Sage Grouse Local Implementation Team, Jon Dinkins is an Assistant Professor in Oregon State University’s Department of Animal and Rangeland Sciences. Welcome to both of you.

Dallas Hall Defrees / Jon Dinkins: Thank you. Thank you.

Miller: So, Dallas Hall DeFrees, when did you start focusing on roadkill?

Dallas Hall Defrees: The Sage Grouse Local Implementation Team here in Baker identified roadkill as being a potential bait, so to speak, for ravens, which are predators to Sage Grouse, back in 2017 when they wrote and published their Threat Reduction Plan for Sage Grouse. So it’s been on our radar since then. I myself have started working on it over the past year and a half or so.

Miller: How much roadkill are we talking about?

DeFrees: That’s a good question. I don’t have a number for you. There’s one highway that runs through Sage Grouse habitat in Baker County that a lot of deer are along. So I’m not sure but a fair amount.

Miller: Jon Dinkins, I gave a two sentence version of the scenario, but can you give us a fuller picture of the intersection between these three animals. I suppose more than deer could be killed by passing cars and trucks, but they seem to be the most likely ones, but how does this trio of animals interact?

Jon Dinkins: Right. That’s a great question. So there’s a wealth of published studies that have made the connection of higher raven numbers throughout the sage brush ecosystem and where greater Sage Grouse habitat is, having a negative effect on Sage Grouse nest success. And then there’s also been several studies that have connected anthropogenic or human related resources contributing to that increase in the raven number. And so the intersection of the roadkill as being a resource that’s available that wouldn’t be available if we weren’t out there, meaning humans out there, contributing to making and generating this extra food source. Then that extra food source…ravens are very intelligent and they’re able to capitalize and use that consistent or relatively consistent resource that is known spatially to ravens. So then there’s also this buffer area that you have, ravens can move long distances so they, while they’re flying to and from known areas where there’s consistent food resources, then they’re inevitably flying over other Sage Grouse habitat and then finding Sage Grouse nests and depredating them.

Miller: Sage grouse adults are relatively big. Do ravens attack adults?

Dinkins: So that’s interesting. So they’re not known to be an adult predator. So they’re not large enough to kill an adult Sage Grouse.

Miller: Which are sort of about the size of a chicken, right?

Dinkins: Yeah. The males are about the size of a domestic chicken, but they have been shown to harass males dancing on leks, so the spring mating grounds in the state of Nevada. So there’s been some recordings of ravens basically plucking feathers out, tail feathers out of male Sage Grouse as they’re doing their mating ritual.

Miller: As they’re trying to attract females with their fancy dance.

Dinkins: Yeah. So no real rhyme or reason why they’re doing that other than, you know, it’s something interesting to do. So, showing the cognitive ability of ravens to be interested in their surroundings.

Miller: So if they’re not in general attacking adults, they’re going after juveniles or eggs?

Dinkins: Right. So they’re the primary mechanism that we know that ravens are impacting Sage Grouses from nest depredation or consuming eggs. If they’re large enough or capable enough to take a small Sage Grouse chicks, them being most likely vulnerable, especially in the first 2-3 weeks of a Sage Grouse chicks’ life. But there’s never been a study or documentation demonstrating that. Sage Grouse chicks are mobile, they don’t stay in the nest, they leave the nest immediately so there just hasn’t been an opportunity to document that interaction with young chicks.

Miller: Do Sage Grouse, themselves, change their behavior or maybe where they’re going to nest based on the presence of ravens?

Dinkins: Yes. So some research that I did about a decade ago really looked at that dynamic of areas on the landscapes of random areas are available habitat for Sage Grouse, comparing the number of ravens at those locations compared to where Sage Grouse select their positions or where they want to be, and we found a really striking difference in the number of ravens being the Sage Grouse were selecting locations where there were fewer numbers of ravens, so potentially suggesting some predator avoidance on the stage grouses’ part and that was for both nesting, where Sage Grouse chose to put their nests and also where they took their birds for their chicks.

Dallas Hall Defrees, to localize this again. So as I know you’re the Sage Grouse Local Implementation Team Coordinator for Baker County. There are five different Local Implementation Teams in Oregon, like yours, that are set up to boost Sage Grouse numbers and in doing so, to prevent the species from being listed as endangered. But I’m curious about the particular land that the highway you mentioned goes through. How significant is that area for Sage Grouse habitat in Baker county?

Hall Defrees: Yeah, so that area is designated as core habitat, which is a designation made by the Oregon Department of Fish and Wildlife. And so that’s really the only area besides a smaller area in the southern portion of the county where stage grouse live within Baker County, so it’s very important.

Miller: And what have you seen in terms of Sage Grouse numbers, either in that area in particular, or Baker County more broadly, in recent years?

Hall Defrees: Sage Grouse population has really declined since about 2005. Since then we’ve had about a 70% decrease in our population. This is not isolated to just Baker County, if you look at populations throughout the state and even throughout the West. Those areas are experiencing similar declines, but it’s definitely something that’s concerning for us.

Miller: So, you’re having a kind of, ‘all hands on deck approach,’ which now includes the idea of reducing roadkill or at least, after there is a dead deer on the side of the road, somehow getting rid of it. How might that work?

Hall Defrees: That’s a good question. As you mentioned, this is one component of a much bigger project that we’re working on, but what we’re looking at is providing an opportunity or an area where roadkill could be taken. Another aspect that we’re thinking about is also agricultural livestock carcasses, because this is a big Ag [Agricultural] area and especially in the wintertime landowners have difficulty burying their animals because the ground is frozen, but they don’t really have a good place to take them, which is I think something most people don’t think about. So we’re hoping that if we can provide an area where roadkill can be taken or livestock carcasses can be taken out of Sage Grouse habitat. We can incentivize folks that take their animals out there and then hopefully reduce this opportunity for ravens in the area.

Miller: Have you found partners who could do that and, and money to pay them?

Hall Defrees: Yes. So we, the Baker LIT, or Local Implementation Team received a Focused Investment Partnership Grant from the Oregon Watershed Enhancement Board which is funding a lot of our conservation work here. So we have funds through that Grant opportunity to work on this project specifically. We’ve also identified some partners here to build a carcass disposal station. We are hopefully going to move forward working with Baker Sanitary, which is our landfill here, it’s privately owned. They are looking into being able to potentially compost carcasses, which I think is a particularly interesting and beneficial way to dispose of them.

Miller: If carcasses aren’t impeding traffic would ODOT help you at all?

Hall Defrees: So right now unfortunately, ODOT does not have removing carcasses from the highway as part of their maintenance plan. And if a roadkill is impeding the highway, they usually just kind of drag them off into the barrel pit or the side which is in their maintenance plan now.

Miller: And that’s fine for cars, but ravens would be happy to go into a little culvert I imagine to have dinner.

Hall Defrees: [laughing] Yeah, exactly. So at this time we are not removing roadkill and that isn’t looking like anything that’s going to change in the immediate future.

Miller: If you’re just tuning in, we’re talking right now about the idea of getting rid of raven attracting roadkill as a way to boost Sage Grouse populations. Jon Dinkins, what are other ways to prevent ravens from eating Sage Grouse?

Dinkins: Right, most of the ways to do that, that are economical and possible over a really large landscape- there are some ideas out there of trying to train ravens to not want to eat Sage Grouse eggs and so you could do taste aversion is a strategy that’s been come up within what Wildlife Damage Management to basically have fake eggs out there or that this idea would be fake eggs that you make taste really bad. So if they, if the animal eats some of them, they were like, ‘oh, I don’t want to eat that again,’ the problem with that type of strategy though is that it’s been shown that it will work, but the spatial extent of the sage brush is so vast that having that a consistent enough thing where ravens within the population would be encountering a fake egg that tasted bad and then also having it look enough like a Sage Grouse egg that they associated those two together is really not going to be an effective strategy over the large spatial extent.

Miller: I’ve read that ravens, they could communicate with each other and tell each other where there are, where there’s good eating. But would they also tell each other, ‘ah, don’t eat those eggs, they taste terrible.’

Dinkins: It’s possible. But the strategy would probably be, how often does that occur? You know? So you think about if you eat lots of oranges right? And only one out of every 1,000 tastes bad, most of the time you’re going to think ‘oh, I just got one bad orange,’ and I’ll keep going and eating oranges. So there has to be that consistent footprint of that occurring.

Miller: And we’re talking about the entire west of the US basically, or at least a huge chunk of it, just millions of acres.

Dinkins: Right. And if you also think about the number of Sage Grouse eggs that they would encounter in Baker County where the population is really small, is not that many. And so that becomes a pretty daunting task. So then what we’re left with is really trying to reduce the ravens wanting to go out into the sage brush. And so some strategies that could go with that is reducing the number of good nesting territories, so places where ravens can put their nests And this is a strategy that ODF and WLIT, then my lab with OSU is helping do assessments on this, of really looking at locate. Let’s reduce the ability of ravens to go out and nest in these areas. And nesting home ranges are smaller for ravens, so they target the area that they’re in more heavily and then they have to feed their chicks. So a strategy, a lethal strategy that ODFW is doing is to remove the nests after eggs have been dropped. And that would reduce the food requirements necessary in the local area. On the flip side, OSU and my lab have another study area that’s a declining population in Cow Lakes, that’s in Malheur County. So just north of Jordon Valley, Oregon and where we’re going and manipulating nests too, but doing it in a nonlethal manner where we’re removing the nesting material. So basically, ravens start to build a nest and the power company’s helping us pull those down on human structures and basically, trying to make it a slightly unfriendly place so that ravens will then move to other locations to try and build their nests – the idea there being that sage brush country doesn’t have that many locations where there’s natural substrates to nest on. Thus there would be fewer nesting individuals out in the sagebrush.

Miller: I wonder if we could take a step back here and put this in the broader context. Of all the reasons that Sage Grouse are imperiled, where does predation from ravens fit on the list compared to other challenges in terms of habitat and a lot of other things that humans are doing, whether it’s energy infrastructure or ranching or anything else?

Dinkin: Right. The broader context is always great to think about. So to quantify it out in the Great Basin, I was involved with a recent study from USGS or led by USGS, where raven depredation in the Great Basin is actually one of the top things influencing Sage Grouse nest success, but that’s not as simple as it seems, because raven numbers have been increased due to all kinds of human activities or changes to the landscape. They’ve been connected to larger fire footprints, you know, so there’s more fragmentation, where there’s more fragmentation there’s  more ravens. So fire is connected to that. They like having tall structures or tall trees that they interact and engage in. So juniper encroachment is another big threat to Sage Grouse, but it can also benefit ravens. Ravens are tighter associated to agricultural footprints and so, you know, where you have agriculture that is a fragmenting source or you lose sage brush habitat for Sage Grouse, but at the same time it’s also bringing in more nest predators. So let’s say they’re all interconnected, if you move to even a broader approach to Wyoming, where I’ve worked in- still work- in the oil and gas infrastructure, and resources like that have food subsidies for ravens, but then also these nest structures. So it’s fragmenting habitat. Sage grouse avoid the structures. They also avoid predators that are there. So it’s really an interwoven habitat fragmentation, plus higher abundance of nest predators.

Miller: Jon Dinkins and Dallas Hall Defrees. Thank you. This was fascinating.

Dinkins / Hall Defrees: Thank you.

Miller: Jon Dinkins is an Assistant Professor at Oregon State University’s Department of Animal and Rangeland Sciences and Dallas Hall Defrees is a Coordinator for Baker County’s Sage Grouse Local Implementation Team.

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