Great. So, happy to be here. I am going to be talking, see if we get it up here. I'm going to be talking specifically about ground squirrels and gophers today. Even more specifically focusing on the use of carbon dioxide and carbon monoxide as a fumigator option for managing these species. That said, I do lots of work with gophers and ground squirrels and with a variety of different tools. So, if anybody has questions about other things towards the end of the presentation, certainly you can feel free to go ahead and address those questions at that time. The other caveat that I'll make before we get started here is that a lot of the work I do is in agricultural situations. So, some of the research that you're going to see, the data was collected in ag settings, but I think it has real ramifications and tie ins directly to some of the situations that you're going to be managing as well. We'll work through that as we go through this presentation.
So, I thought we'd start off today by providing at least a little bit of background information, about ground squirrels and gophers. I think this certainly helps and understanding how some of these different tools can potentially be used to manage these species. And so let's jump right into a little bit of this background information. Starting off with the California Ground Squirrel. I'm sure you're all familiar with what ground squirrels look like, but you'd have to have their obligatory photo just to show everybody, right? So, they are grayish brown in color. They have a semi bushy tail. They oftentimes have a speckled type appearance on their fur as well. If you're ever in doubt about whether or not you're dealing with tree squirrels species versus ground squirrels, one of the easier strategies is to simply chase the squirrel and see what it does. If it goes down the burrow, it's a ground squirrel. If it goes up a tree, it's a tree squirrel.
Sounds pretty simple and it is, right? Tree squirrels don't run into burrow systems to get away from danger. Ground squirrels, although they definitely do climb trees, don't climb up trees to get away from danger. They're going to go down their burrow systems. So, that's one good diagnostic there. Now they are social, so we do see them living together groups. That's usually a good thing for us from the perspective of being able to identify them out there causing damage. If you think about some of the other rodent species that are out there it's often times difficult to see them, figure out which ones are causing specific damage in a given situation. With ground squirrels, we don't usually have that issue. The damage they cause can be quite extensive and quite varied. Certainly they will girdled trees.
So, like I said, they'll get up in the trees sometimes and they'll chew the bark off of some of the branches. They don't usually get as high up in the tree as the tree squirrels do. And so you may see a lot more common girdling damage higher up in the trees from tree squirrels. But we do see this to some extent with ground squirrels as well. Certainly they're going to consume forbs, grasses, plants in gardens, things like that. They chew on irrigation lines. This is a very common form of damage that we see from ground squirrels. And then their burrow openings caused lots of potential problems as well. Certainly there are hazards on parks, athletic fields, playgrounds, situations like that. We definitely see increase soil erosion concerns with ground squirrel burrow systems. You get heavy rainfall events, the water starts to channel down through that burrow system, leads to a pretty substantial erosion slumping on hillsides, things like that.
So, we certainly have those potential concerns. So definitely lots of concerns associated with ground squirrels. Now ground squirrels are diurnal. That means they're active during the daytime. So again, it's usually pretty easy to tell. You've got ground squirrels, you see them running around out there, you know, they're there. And as the name would imply, they do live in burrow systems. And so this burrow system sometimes go up and underneath structures. That's another potential concern there. But there's lots of other places that they like to burrow in as well. Brush or pruning piles are an example of one of those preferred harborage sites. And so if you're thinking about IPM, you're thinking about habitat modification, getting rid of these kinds of brush or pruning piles, woodpiles trash piles, junk piles, anything along those lines. It can be really good harborage not just for ground squirrels but for lots of species out there. You also find them along field edges, fence rows, roadsides, those kinds of connecting type, habitats out there. So, these are some good areas to key in on when looking for ground squirrels moving into certain areas. That said, once it becomes established, you'll find ground squirrel, burrows systems all over the place. But these are some of the areas to look at when they're starting to invade and populate a certain area.
Is there any new evidence about, and I hope I don't repeat this question, but is there any new evidence about their preference for being able to see having a clear vision around them so they can see predators? I remember, there was a whole effort to--one control tactic was to erect some sort of visual barrier in the hopes that they wouldn't like to live there anymore.
Right. So, the question was, I guess more of, yeah, can visual barriers be used to deter them from moving into certain areas, for example. And I know they did test putting up some kind of a fencing structure that was completely obscured trying to keep them from moving into certain sites. I think it had some benefits, but they also eventually figured out how to get around and through that structure as well. They are very visual. They are a very visual species. They observe looking for predators coming into certain areas. They communicate very well. They have very specific chirps that they can use to let other individuals in the population know that, "Hey, there's a raptor coming," versus a terrestrial predator, things like that. So they are able to, to chatter back and forth and let each other know what's going on out there.
And they do a lot of that through their own visual eyesight. So yes, you know, putting up some kind of obstruction may at least slowed down some of that movement into certain areas, but my guess is it's probably long-term not going to necessarily solve the issue. But if you use it as part of an integrated approach, again, maybe there could be some potential benefit to that.
What about high grass versus short grass?
High grass versus short grass, yeah. The thing about ground squirrels though is that they can go out there and mow it down themselves. So, you know, when you think about all the vegetation that gets removed in a certain area, and a lot of the livestock producers, for example, deal with this on a regular basis because the grass is what they're using to feed the cattle, right? And so they oftentimes think about--we often think about ground squirrels and the amount of forage that they consume and what kind of impact that has on livestock producers. But really the vast majority of the forage that gets removed is actually what they're removing just to keep things clear and devoid and open so that they can see out there. And so, leaving tall vegetation, my guess is they're just going to mow that down pretty quickly too if they move into a given area. Yeah. But it really hasn't been looked at super extensively.
Now we also have gophers and we're going to spend quite a bit of time talking about gophers today too. They are burrowing rodents too, about six to eight inches in length. Of course you don't usually see them up above ground, right. So for us to know that gophers are present in an area, we have to look for some other form of sign and of course what we're looking for are there mounds. On this photo at the bottom right it gives you a good indication of what a typical gopher mound will look like. Usually horseshoe shaped in appearance with a plug towards the lower end of one side of that mound. Contrast that to mole mounds, which tend to be more conical or volcano shape in appearance, with the plug either the right in the middle of the mound or sometimes you just simply don't see the plug in the mound.
It certainly is very important that you can discern the difference between these two mounds though, because these two species are quite a bit different. Gophers are rodents so they're feeding directly on plant material. So, they're generally going to cause more direct damage in that capacity. Whereas moles, they're insectivores. They're eating worms and grubs and things like that. So, they're generally not causing as much damage directly to the plants. Now of course their mounds cause the same general concerns that gopher mounds do. So, if that's your biggest concern, then they're both going to be relatively equivalent as far as damaged. But if you're more concerned about direct damage to vegetation, gophers tend to cause damage, yeah.
Are moles [inaudible]?
No they're not. They're insectivores. They're an entirely different order of mammal. Yeah. Now it's also important to understand that because these two species are quite a bit different management strategies for the two are going to vary quite a bit too. So, if you wanted to use traps to manage gophers and moles, keep in mind the traps are generally different that you use. I know that we don't focus too much on rodenticides here, but if you wanted to use, you know, toxicants to manage moles versus gophers, those are quite a bit different. And even the burrow fumigants, they are really-- we're going to be talking mostly about fumigants today and there's a fair amount of good data out there on the efficacy of fumigants for gophers. But there's really almost no data out there for moles. You know, oftentimes we don't really focus on the use of fumigants for moles because moles tend to have pretty shallow burrow systems.
Also, from a human creation perspective, it's probably not quite as good for moles either. So, definitely important that you can discern the difference between these two species there. Now as far as damage is concerned, with gophers, of course they feed directly on taproots, thereby weakening and or killing those particular plants. Probably the most common form of damage that we see from gophers. But they can also girdled trees, particularly below ground. And here's an example of what that girdling damage can look like. Even though it looks like it occurred above ground and actually did occur below ground. We just removed the soil from around the base of the tree to expose that girdling damage. And of course because it's occurring below ground, we can't see it. So, we don't generally know that it's occurring out there until we start to see a loss and vigor of that particular tree.
And at that point in time it's usually too late. You probably going to lose that tree. And if it's happening in one tree, it's probably happening to several of them out there. So, we can see some pretty high mortality pretty quickly, particularly when we're dealing with younger trees. And of course their mounds cause lots of potential concerns as well. Again, they are hazards on-- tripping hazards in parks and on athletic fields and places like that. They can kill plants directly just by burying them. When they bring the soil up to the surface, they're bringing weed seed with it. So, we can see a proliferation of weeds associated with these mounds. We have increased soil erosion concerns, etc. So, lots of general concerns when it comes to gophers as well. Now we certainly do recommend that to the extent that you can, that you utilize an integrated approach when it comes to managing both gophers and ground squirrels. You're generally going to find better results if we, if you use multiple techniques rather than if you rely on any single one approach and certainly there can be a number of different examples that you could provide.
One example might be to use borrow fumigation as an initial tool to reduce populations in a given area. But it's important to remember that not all individuals in the population are always going to be equally susceptible to all the different techniques that are out there. So, sometimes it some mixing and matching and so maybe after a fumigation approach, you'd come back through with trapping to further target some of those remaining individuals in the population. Point being, it's really important to try to mix those tools up so that you can effectively target all the individuals in there in a population rather than just relying on one tool. So, to the extent possible, I strongly recommend that you try to mix things up from time to time utilizing different strategies. It's also really important to understand a little bit about the biology of the species that you're trying to manage as well as the ecology of the system that you are working in, as this can greatly influence the efficacy of management programs too.
And this chart I think does a really good job of illustrating this. This chart with designed specifically for the California Ground Squirrel and what we have on this chart are major activity periods for ground squirrels, major food sources, and the best time for control, or three of the more commonly used strategies for managing ground squirrels. And of course this is broken down across the different seasons of the year. So what do we see when we look at this chart? Well, one of the first things I look at, I'm looking at activity periods up here and I see the ground squirrels are not necessarily active throughout the year. In the winter time, ground squirrels oftentimes hibernate. In fact, most of the times they hibernate. In some settings they don't, but usually they do at least for a short period of time. So, if the ground squirrels are hibernating, they're not active, we're not going to be able to effectively manage them.
That applies even to the burrow fumigants. A lot of times people think that ground squirrels are hibernating. They're in the burrow systems. We know where the burrow systems are. Why not just apply the fume against then? The problem is, is that when they're hibernating, they plug themselves up and inside the little chamber deep down within their burrow system. So, if you put the gases in there at that time, those gases are not going to get to them within that little chamber in that burrow system. So, you really need to wait until brown squirrels are active above ground before you can use fumigants. So keep that in mind. They do hibernate. Management during hibernation period is not going to be effective. Likewise, in the middle of the summer, ground squirrels often estivate. Probably not right here. It doesn't get too hot. But for those individuals more towards the Central Valley and some of the warmer locations they do estivate during the middle of summer. Estivation is basically another mini period of inactivity.
It's basically so hot. There's not enough food out there for them to really stay up and above running around. So, they just sleep it off. The juveniles will be active. You will still see some ground squirrels running around even during this estivation period. But if you're going to put together a cost effective management program, that's probably not the best time to target your management because you're only going to be getting rid of a certain portion of that population. If you're actually going to try to manage the population as a whole, better to do when they're all active. So keep that in mind too. Yes.
Does that apply to the coast as well? The estivation period?
That's what I was just saying, you know? Right. In some of the cooler areas, they probably don't estivate as much, but you said you had some people maybe towards the Central Valley or whatnot where it's a little bit warmer and in those settings then they will estivate, yeah. But right here probably not as much of a concern. No.
Now it's also important to remember that the different techniques don't necessarily work the same throughout the year. For burrow fumigants to work, and we're going to be talking a lot about fumigants today, for them to work you need relatively high soil moisture. Of course here, we get a lot of our soil moisture in winter through spring time, so borough fumigants tend to work really well this time of year. When you have high soil moisture it closes off the pores in the soil, closes off a lot of the cracks, seals them up and holds those gases in at a really good rate. So once the soil starts to dry out the fumigants don't work very well anymore. So, if you're going to use fumigants you need to focus them on areas and situations in which you have relatively high soil moisture. If you have higher soil moisture later in the year, if they still work, it's not specific necessarily to a certain time of year.
It's specific to when we generally have most of our soil moisture. So, that's an important consideration to keep in mind. One of the nice things about trapping is that trapping can be effective year round as long as ground squirrels are active. So, trapping is always a great alternative approach to use for ground squirrel management to target some remaining individuals when you can't use burrow fumigants. So, these are just a couple, a few examples, of how it's really important to know a little bit of information about the species that you're trying to manage as well as the ecology of the system that you are working in, as these all do influence the efficacy of management programs. Now for gophers it's probably a little bit less important because gophers are active year round. They're not hibernating, they're not estivating, so you don't have to work around some of those issues.
Certainly, soil moisture is still a key component. So, keep that in mind when you think about gopher management. But beyond that, there isn't necessarily any one time in the year that it's better to focus on gopher management than any other. It tends to be a little bit easier to focus on, gopher management when we've had pretty good precipitation when you have good soil moisture because that lends to greater mounding activity. And then also it makes it just easier to probe and find burrow systems to set traps, to utilize burrow fumigants, et cetera. But as far as being able to manage gophers, you can manage them year-round. Now, certainly we do have a variety of tools that are available for use against both gophers and ground squirrels-- a habitat modification, bait application, burrow fumigation and trapping are probably the tools most commonly used when it comes to gopher and ground squirrel management.
Exclusion can be used on limited scale for gophers. So, if you're thinking about wire baskets around the root systems of newly planted trees, that's good on a small scale. Large scale, it tends to be less practical, raised flower beds, things like that. They're all effective at keeping gophers out, but they do have some limitations based on the area that you can cover. Ground squirrels, there really hasn't been much on exclusion that's been effective. There was the one study where they looked at putting up the physical barrier to keep them from being able to see across and it did have some short term benefits, but the problem is ground squirrels do climb really well, so they can oftentimes get around structures. They obviously dig very well, so they can dig underneath and around a lot of structures too. And, they can dig pretty deep, several feet at least.
There are some studies showing six, seven feet deep or more, in some settings. And so it's really difficult to try to exclude them from certain areas. So, we oftentimes don't focus on exclusion for ground squirrels. Repellents and frightening devices. You know, there's lots of these things out there on the market. But to date, there's really no studies that have ever shown any repellents overly effective for ground squirrels or gophers. Same thing for frightening devices, vibrating stakes and little windmills and things like that that you sometimes see. There's really no evidence to suggest that those are effective long term either. And shooting, you know, shooting can be used for ground squirrel control, but of course there's many areas we can't use shooting. So, it's not going to be a very practical tool I think for your settings here. So, with that kind of brief overview we're going to spend, yeah, go ahead.
For the gopher baskets? If you build it will they just come to the surface crossover it?
Yes, yes, yes there is. So, you have to have them extend above ground. If you're going to expect long term applicability with this. Gophers don't climb really well but then climb a little bit. So, I'd like to see at least one foot, extending above ground and potentially even a little bit more than that, although you know, then it becomes a little bit less practical for you. So, 12 inches is usually pretty good.
Many people have said to me, well they I don't like, but I'm speculating that perhaps a sense subtle atmospheric pressure changes [inaudible]. Have you ever heard that it affects their ability to sense pressure?
No. So the question is, he commented that he's had some efficacy with castor oil type repellents and wondered if it impacted their ability to sense changes in barometric pressure or something else along those lines. The short answer is, I don't know. There has been some studies done with moles and they did find that castor type repellents actually were somewhat effective against moles. They have been tested against gophers and some of the testing that I've seen, it didn't work. But that doesn't mean it doesn't work in some localized situations, at least to a limited extent. So, you may see some benefits whether or not that impacts their ability to sense things or whether or not as some kind of a skin irritant or something along those lines. I've never seen anybody at look at that issue. So, I really don't have any kind of a response on that. My guess is it's probably more of a deterrent because of, whether it's an odor or some kind of a skin irritant or something along those lines. But that's just a guess. I really don't know. The only study that I've ever seen that was able to prove any kind of potential impact on gophers was a capsaicin type, repellent. And they really saturated the ground heavily with it. To the point where they didn't consider it an overly practical tool to use, but that did cause some lessening and gopher activity in that particular area.
And that would definitely be a skin irritant there. We have incidentally, that we've looked at, I particularly in particular have looked at certain kinds of repellents, putting them on like, irrigation tubing and potentially on woodblocks to simulate trees and things like that. And we just have not had any success in keeping gophers from chewing on things, even with these various different kinds of repellents out there. So, there may be some potential utility for short term elimination of gophers from particular areas, but longer term, I'm not sure how well that would work, but who knows.
Alright. So, now we're going to jump into the meat of the discussion here today and that is talking about the use of certain specific burrow fumigation options. In particular, the use of carbon monoxide and carbon dioxide as a burrow fumigants. Carbon monoxide was the first one that was legalized for use here in California. So that's first one. I'm going to start talking about. Historically the use of pressurized exhaust or carbon monoxide actually was not legal for managing burrowing rodents in the state. It wasn't legal until 2012. Basically, Assembly Bill 634 was passed in 2011 that allowed it or legalized it for use against burrowing animals. And it's been legal in all other states basically since the beginning of time, if you will. So, there had been a few products out there on the market before, this assembly bill was passed and the one that was most readily available and the first one that was developed was this right hear.
And that's the PERC machine. PERC Stands for pressurized exhaust rodent controller. It's basically a small engine, creates exhaust, pumps it through these coils to cool it off and then stores it in a large compressor that basically compresses that exhausts, allows you to use a series of hoses and probes to inject that exhaust directly into the burrow system. I believe it's about 25,000 ppm, something along those lines. It's a really high concentration. After that one came, the Cheetah rodent control machine, it's essentially a glorified leaf blower if you will. It creates exhaust and you use this little tube to get the carbon monoxide or pressurized exhaust into the burrow system. Because of this specific design, it's mostly used just for ground squirrels. There is no great way of using it to get exhaust into gopher systems. If you go to the website, they tell you, you can find the open gopher tunnel systems and use it to inject the exhaust into it.
But we all know gophers keep closed burrow systems the vast majority of the time. So, it's kind of a real hit or miss proposition for gophers. After that came the Gopher X, they recently changed the name to the Burrow RX, so you may know it under either of those names. The benefit of these two designs obviously is that they're more portable, so it's easier to carry around. They're certainly cheaper. $1,000 to $1,500 for these verses six to $16,000 for one of the PERC machines depending upon what size unit you get. So, there's definitely a cost. The other advantage to the Burrow RX is that it has an additive that you could add to the fuel which creates smoke. So, when you're putting the exhaust into the tunnel system it is creating smoke. You see where the smoke is coming out. In other words, sites that might be connected to it. So, you can go and plug those sites up as well.
With these two devices, there is no smoking mechanism, so you're not quite sure what's connected to what. So, that can be a real advantage there. And then more recently I found out about this one here. This one's called the CO Jack. It's pretty similar to the PERC machine. It's a larger device. You'd have to pull it around, but the real benefit of the CO Jack and the PERC machine, as you can see here, they have multiple hoses and probes. So, this allows you to potentially treat multiple burrow systems at once. The PERC machine in particular comes up to a unit, the largest size is a unit that has six hoses and probes. So, you could in theory be treating six burrow systems at once. So, that is an advantage that would allow you to move to areas more rapidly. So, you always have to consider that. Certainly, the unit cost is more expensive, but you can save labor costs potentially by moving through areas more rapidly.
Then there is, real recently, the use of carbon dioxide has been legalized. In particular, there's a device called the Eliminator, which is what this is right here. It was just approved for use within the last, I don't know, two or three months I guess, maybe. And they've been trying to get approval for many years. And they finally got EPA and DPR approval for it. This is a little bit different. You basically have to go out and buy a canister of carbon dioxide and then it has a specific application device that you use for, to probe and inject the carbon dioxide into the burrow system.
Is that expensive?
So, it's interesting, all you are really purchasing is the little probe type device and the regulator that goes with it and it's like $1,000 for all of that. So yeah, it is kind of expensive and then you have to get to the tank of carbon dioxide and of course the tank only lasts a certain period of time, then you have to go buy another tank. So, it does have some limitations there. Presumably the cost for it, why it's so expensive is that when you pump carbon dioxide out at a higher rate at tends to freeze up and they have a specific regulator designed to not freeze up. So, I guess that's where the cost is supposed to be at.
So, with the advent of these two different tools you know one of the questions is, is what are they providing to us that some of the elder options out there weren't providing initially? And one of those is potentially is that these could potentially be safer for the applicator, particularly when you compare it to aluminum phosphide and any of you who've used phosphide or [inaudible] in the past know that you definitely have to be very careful with how you use it. There tends to be less risk associated with both the carbon monoxide and carbon dioxide approaches. That with the PERC machine, if you go to their website, they actually did a study a number of years ago where they looked at above ground exposure of carbon monoxide to the applicator's and it was quite low. So, certainly carbon monoxide is obviously toxic to humans, but based on this application design, there were no real perceived risks associated with it.
Carbon dioxide should in theory of course, be even safer to use. And so that's one of the selling points of the Eliminator. And then also you have the capability of treating multiple burrow systems at once if you're using the PERC machine or the CO Jack. So again, that allows you to move through areas more rapidly and potentially save on labor costs as well. So, those are a couple of potential advantages. Questions of course are on the efficacy, hadn't been tested, we don't know how well they work. So, we needed to address that. And then also what does the cost effectiveness or practicality of utilizing devices. Because there is a fairly substantial outlay in costs initially when you purchase these machines and how does that relate cost-wise to some of the other tools that are out there as well. So, we set up a number of studies over several years. Yes. Question?
Mostly you were talking about like the larger area, you know, covering more area. What could you use something like dry ice for something smaller like a lawn or something?
Right. So, the question is could you use dry ice instead of one of these fancy machines to get the same results? It's kind of a two-pronged answer to that. The short answer is, not really because it's not legal. And hasn't been approved for that use. And to use it in that capacity, you would be using it as a pesticide. You would have to have a label to do that. It's not approved for that use. Not for ground squirrels, not for gophers. So, technically it's not a legal option for you at this time. Would it work? Probably if you got enough dry ice into the burrow system. And I think it's something that, you know, they're continuing to consider. It is available again for rats, right. If you can find, if you can find the product. But it has at least been approved for Norway rat control.
But yeah, there's a lot of hurdles to using dry ice, particularly for getting an approved, once you, even once you have an approved label for it. Part of the problem is, is when you go buy the dry ice, you know, it starts shrinking immediately after you buy it. And so, you have to use it immediately in order for it to work. And how does the distributor make money doing that with a labeled product? That's one of the hurdles they're running into, right. Because you can't just go to the grocery store and buy dry ice and use it in that capacity. It's not legal in that manner. It has to be a certain approved product for it. So yeah, it's just not an option right now. It would certainly be simpler and probably a little bit cheaper on the small scale, but just not an option right now.
Let me add in on that.
I talked to DPR about this whole thing a year or so ago. And if you are a homeowner, it's kind of like vinegar for weed. It would be legal for a homeowner to go put dry ice into a burrow.
Really, they said that would be okay?
I mean it's, and on the weed we had it for a short time. We had a labeled as a 25 B product, an exempt product but that got rejected. And then, what else was I going to say? Yeah. So, and I think they bought that dry ice at Walgreens, some Walgreens when we did our trials. It was pretty effective on rats.
By all accounts it is pretty effective.
We had to make sure to get every burrow once. So, it's kind of a bureaucratic, sad bureaucratic story right now.
Yeah. It's not that it wouldn't work, it's just what's allowed for us at this point. Yeah. Okay. So, you know, one of the first steps obviously that we were interested in was testing the efficacy of these products. There's no point in looking at it further if it's not efficacious. And so that was our initial focus. And so initially we set up some studies up in the Klamath Basin testing the PERC machine for ground squirrels and for gophers. We also set up a study in Fresno County on this case, looking specifically at the Cheetah Rodent control machine on how effective that would be for ground squirrel management. Then we started looking at the PERC machine for California ground squirrels in Alameda County. You will notice this was really dry conditions and we'll hit on the importance of that here in a little bit. And then we also tested it in an orchard setting for California ground squirrels and more ideal soil conditions settings.
And then lastly, I have had a little bit of testing experience with the Eliminator. Again, this was a hot dry condition in an abandoned orchard. Now as far as the application process is concerned, as with any method for gopher or ground squirrel control, you first have to find active burrow systems. It's not going to work if you don't find active burrow systems. So, you'd go out and look for the most fresh mounds. You go out and look for the most fresh ground squirrel activity. Once you find them, you then insert the probe for gophers. You find the mounds, you probe around just like you would if you were going to apply bait, if you're going to set traps, et cetera. Once you find that burrow system, you then just crank a lever and it starts shooting the gas into that burrow system.
Same thing for ground squirrels. You find the burrow system, insert the probe. Usually we'd take a shovel full of dirt and kind of pack that in and around the probe so that it would hold gas in and then you turn it on. How long do you run the gas for? That's a great question. Don't really have the answer for that yet, at least as far as what is ideal. I can tell you that the manufacturers, for pretty much all the machines, generally recommend around three minutes. So, that's usually what we use. We usually, inject the gas for about three minutes. Of course, you know, this is just as much of an art form is trapping is and some of those other tools out there. So, if you think you see a burrow system that's a little bit larger, you might decide you want to run a little bit more gas into that burrow system.
And in fact, in one of the study sites we used, we had a professional applicator who was doing all of the applications and they had large burrow systems out there. They preferred to run the gas for closer to six or seven minutes. And that was based on his general experience out there. So, people do have different opinions on what's appropriate, how long you need to run it. I don't have the answer for you actually tried to get some funding to look at this to try to narrow down how long we need to run it. But we didn't get it funded.
Right. The question is, are there negative ecological effects for running too much gas in there? No, I don't know of anything that would be, it's carbon and oxygen basically. So, outside of potentially non target species being in the bureau system, there really shouldn't be any negative impacts. And running it for three minutes versus six minutes wouldn't have any more or less impact on the non targets as it would for the ground squirrel or the gopher. So, running it longer, I don't think probably has any real potential impact there.
What about on a Levy system generally? I mean, what did they do?
They use a variety of different tools and it varies from county to county, location to location. Some people still use rodenticides extensively. Some people prefer aluminum phosphide, some are running these kind of pressurized exhaust machines. Some went to mostly trying to use raptors, so it varies. Some still use trapping heavily. So, it's really kind of depends on county restrictions and who's in charge of the applications and what they want to go through. So, we see all kinds of different options you used out there.
So yeah, duration variable. Wish I had a better answer for you on that. All I would say is that most people use about three minutes, so that's probably a good starting point, at least for you. And then when you're done, obviously for Gophers, you're going to pull that probe out and you're just going to cover that opening up just so the gas holds within that bureau system. Same thing for ground squirrels. You're going to pull that out and plug up any kind of opening that might potentially be left there. So again, that you're sure maintain that gas supply in there. With ground squirrels--also, I always try to look at some of those adjacent openings. You can usually see if there is a little bit of air movement or something along those lines. And if there is, then I plug up those openings too. If ever in doubt, I just go ahead and reapply that next opening to try to maximize the likelihood that we got them. But again, that gets back to kind of, you know, one of the benefits of that Burrow RX machine is it creates the smoke. So, you do know what's connected to what. So that can be an advantage. Did you have a question?
Do you ever plugged in beforehand just to keep it contained?
If, you knew that something was connected, then yeah, absolutely. I would plug those other openings. Yeah, shovel it in.
And do you ever see ground squirrels running out or the other holes?
Have I ever? I'm not sure I ever have. Certainly not on any kind of consistent basis. They don't know. So, that doesn't seem to be an issue there.
I was curious, and this relates to it relates to the dry ice thing too, if they would detect this hissing of this gas coming in and start running or blocking tunnels or what not.
Right. So, one of the theories why it may not always work is that maybe they do detect that, and they plug themselves up somewhere within there to where the gas doesn't get to them at a high enough rate. I think that's probably more likely for gophers than it is for ground squirrels. Because it's really easy for a gopher to throw up a plug in their tunnel system in matter of just a few seconds. Ground squirrels, that's a little bit harder to plug up. You know, that part of the tunnel system. And which is why I think we generally see better results for ground squirrels than for gophers for all fumigants regardless of the fumigant type. But no, we don't really ever see him come screaming out of the tunnel system or anything like that. And one of the benefits potentially of, you know, these kinds of pressurized exhaust systems is that you're putting in really high ppm immediately. Whereas with dry eyes, with aluminum phosphide it takes time for that gas to build up. And so, they have time to decide; do they want to leave, do they want to throw up a block in the tunnel system, etc. With these kind of devices you're hitting them with high concentrations immediately. And so, in theory, the animal will pass out and then succumb to the product within a matter of a few minutes after application.
So, how efficacious were these products based on the studies that we looked at. For gophers, I would classify it as moderately effective. We averaged about 60 to 65% removal rates. Contrast that with some other tools out there; trapping, we oftentimes see 90 plus percent removal, aluminum phosphide, we regularly see 90 plus removal. Even if we were strychnine baiting, we usually get better results with strychnine baiting. So, it wasn't the magical panacea out there when it came to gopher control, but it wasn't horrible either. It was decent control and consider that we can treat multiple burrow systems at once. There is an advantage to that, and I'll show some data on that here in a few slides and also keep in mind that particularly for you all, there are a lot of these tools you can't use on a consistent basis. So, having a tool that's at least moderately effective that you can use is better than not having anything at all. So, there's some benefit there.
These were two treatments through a particular field, generally speaking. Yeah. The first one might've only been one. This wasn't my study. It might've just been a single application, but for the studies I was involved with, there were two applications. So, we also looked at it for Belding's ground squirrel, which is a different ground squirrel species found in the northeastern part of the state. It worked better for Beldings. We had 76% removal rates, anything above 70% we consider it to be a pretty good tool. And we were definitely above that. And this was with one of the original machine type devices. They've made a lot of advancements since then. So, my guess is that it probably works a lot better for Beldings now than it did in that study. I base that guess in part on some of our work for California. Ground squirrels were when we were dealing with ideal soil conditions, we had 100% efficacy with the PERC machine for ground squirrels.
So, it worked really well in that setting. We looked at it, if you think back to those dry conditions I was talking about, we actually had 66% efficacy in those dry conditions. Fumigants aren't supposed to work when you have dry soil conditions. Yet, this was still working fairly well. I was really surprised pleasantly how well it was working in those dry conditions. The reason we did it in those conditions is because I thought it might work better in dry conditions because it's pressurized. You're putting tons of this gas into the burrow system in a very short period of time so it doesn't have as much time to leach out through the soil. And I think that's probably what was happening. So, even in dry conditions, it's not ideal, but it works okay in dry conditions.
Sure. So, what we can do, what we generally do is we use monitoring tools to assess relative efficacy. So, for ground squirrels, what we do-- there are ground squirrel counts. We set up monitoring plots. It's about a one-acre plot. We go out there before treatment, we count squirrels, we count them 10 times a day, usually five in the morning, five in the afternoon, separated by five minutes in between each count. We do that for three days. So, we have 30 counts squirrels basically. And we take the maximum amount that we have. That's our before treatment number. Then we go ahead, we do the treatments and we come back after several days after and we repeat that whole process again for three days. And we take that maximum number left after the treatments that we do a before and after comparison to come up with overall efficacy. So, it's an index of relative index of overall efficacy.
This is not photographic. Nope. This is visual observation. For other species, we do use cameras for photographic evidence in some cases. Some studies, I've got one going on right now, we go out and actually physically radio collar individuals. Those are probably the most accurate assessments because we have true measure of survival during that process. And so, we can directly assess mortality, but that's more complicated. You got to go out, catch, put the collars on, you've got to track them, et cetera. So, that's not done very often. We usually use these more indirect measures. For gophers we do use what we call an open hole method. It's kind of an occupancy assessment. We have a bunch of different plots out there. In those plots we dig holes down into gopher tunnel systems. If they plug it up, we know they're there. If they don't plug it up, they're not there. And so, we do a before and after assessment with our treatment types there too. So again, it's a relative measure of efficacy.
So Perc machine, I'm rather bullish on for ground squirrels. I think it's a really good tool for ground squirrels. I think it's a moderately good tool for gopher control. But we did look at the Cheetah Rodent control machine as well. You see, we actually had more ground squirrels after treatment then before treatment. So, the Cheetah, not quite so excited about. It certainly is cheaper and more portable, but the design just doesn't seem to be quite as good as some of the other products out there. So, at least based on our trials, it wasn't working very well. Now we did look at the Eliminator as well. Now, we only had 44% efficacy with the Eliminator, but there's some very important information, very important caveats to this. Again, we were dealing with really hot, dry conditions at this site. So, I don't consider this to be an overly representative study of this product.
Also, at this site, it was an abandoned orchard, so they had a lot of old trees, law of the burrow systems were up and underneath the root systems of these trees, the trunks of the trees. So, there are lots of large cracks and crevices. And so, I think that the gas has had a lot of areas to dissipate in. And so, I actually don't put any credence to this value at all. Since we're talking about it, I thought I would show it here today, but otherwise I generally don't even talk about it. What I will say is the manufacturer has had independent testing of the product for both gophers and ground squirrels. And I don't remember the exact numbers. I don't have the study available to me, but I did see a presentation on at one time and they had 90 plus percent removal rates with the Eliminator for gophers and ground squirrels based on their study.
So, my guess is that this is actually a pretty good tool when it comes to gopher and ground squirrel management at least if you use it in the good soil moisture type conditions. So, it's probably okay, but I don't have a lot of data myself explicitly on it. So, those are devices that I do have data on. I don't have any data on the Burrow RX. I don't have any data on the CO. Jack. My guess is that they work fairly similar to the PERC machine. In other words, I think they probably work relatively well. That's based on external feedback that I've gotten from people who use it combined with the similarity of the design of those devices compared to the PERC machine. But I don't have any explicit data on it. So, that's efficacy. But we're also interested in, you know, how costly is it to utilize these products?
Is it reasonable and practical for us to use it. So, I do have some data for ground squirrels and for gophers. So, this data first off is for ground squirrels and what we have is the efficacy value in the blue lines and dots. And then the cost is represented by the red bars here. And what I have is data for the PERC machine, gas cartridges, aluminum phosphide. So, three burrow fumigants here and then a 0.01% broadcast application of diphacinone. Now there's a real important caveat to this particular comparison here and that this data was not head to head. In other words, we didn't collect all this data from the same fields at the same time. So, you have to take this with a bit of a grain of salt. I would look at large contrast rather than specific numbers here.
And the other thing I'll point out is that for the PERC machine, this cost is based on a $60 per hour charge. In other words, we hired somebody to come in, do the applications at $60 per hour so we didn't have to pay for the machine, but we're paying for the utilization of the machine and the labor to do so. And what we found out is that with the PERC machine and gas cartridges, they were the most expensive option that we had per hour. Aluminum phosphide was quite a bit cheaper. And then the broadcast application, a diphacinone was of course the cheapest of them all. Efficacy-wise, aluminum phosphide and was generally the most efficacious, which shouldn't be surprising. It's been known to be highly efficacious for a long time. Otherwise, the other three tools, we're all fairly consistent overall efficacy. So, what this would suggest is the perk machine is relatively efficacious, but it is also pretty expensive to use if you're hiring somebody to come in and do those applications.
What would happen if we bought the perk machine and then used it? How would that change, uh, this dynamic of cost? So, for this we had to amortize the cost out over time because obviously when you buy the machine, you have a very expensive cost outlay initially, but that cost will go down and over time the more and more you use it. And so, what we did is we collected data there on daily costs per barrel system that we were treating. What we have is data for aluminum phosphide keeping them aligned with aluminum phosphide your only costs are buying the aluminum phosphide and the labor to apply it. So, there was no amortizing of costs needed there. Same thing for gas cartridges. So, pretty flat. For PERC machine, obviously if you're only going to use it a few times, that cost is going to be really high because the cost of the machine is really expensive.
But as you use it more and more over time, that cost is going to slowly start to level off. We had two different kinds of studies where we were looking at the one study side. I told you we had an average application time of six minutes. One of the costs of applying more gas is that it's going to take you longer to go through an area. And so that is represented by these dashed and dotted lines here. And the completely dotted line is representative of the three-minute application. Long story short, I didn't take long before the PERC machine got below the cost per burrow system of gas cartridges. Gas cartridges are pretty expensive on a per burrow system basis, so we can certainly get below that pretty quickly and I think it's probably a little bit more efficacious than gas cartridges overall. So, I think there are definitely some benefits there. If we look at it for aluminum phosphide, if we were doing three-minute applications, eventually we got below that cost level. But you had to use it for about 700 days or so. So, it takes a long time. Now in theory, these machines should last for a number of years, so you can use them an extensive period of time eventually getting that cost down below the aluminum phosphide costs. The six-minute applications actually never did get below.
It's some kind of a carbon, I forget carbon something or other. Basically, the primary gas that kills the ground squirrel is carbon dioxide. It's not the sulfur in it. A lot of them do have sulfur in them though. But there are different, there are different gas cartridges and they have different compositions. So, some of them are more heavy on the sulfur side. Some of them are more heavy on the charcoal and carbon thus carbon monoxide side of it.
Yeah. If you're talking about like the giant destroyer and the, there's another gopher bomb or something like that. Yeah. I Gopher Getter. Yeah. Which incidentally, they don't work well for gophers, so that's always comical anyways, so you can see that there is definitely a cost. It takes a while, but if you're somebody who's going to use it a lot, eventually you can get to that area where it's probably fairly comparable to some of the other options, but it takes a long time. Now we also have data for gophers as well and this data is a direct head to head comparison. So, I would place more weight on the exact relationship between this data collected here. So first off, I wanted to show overall efficacy that we saw from this head to head comparison. You can ignore the blue bar for today.
That just represents three trapping sessions. That's part of a different discussion there. In particular, look at the efficacy for the red bars, that's for trapping and aluminum phosphide. There was no statistical difference in efficacy between these two approaches. They both were highly efficacious. The PERC machine you can see was a little bit lower. I think the overall efficacy in this study was about 56%. So, not as good, but still some level of efficacy. And keep in mind, we can treat multiple burrow systems at once. And that gets us into this data here. So, what we wanted to do in this particular case is relate the cost on a per gopher removed basis. In other words, first we wanted to determine how many gophers would we remove in an eight hour a day, utilizing trapping, aluminum phosphide and the PERC machine.
And that goes back, there's a lot of equations involved with this. We're not going to get into the weeds there. But basically, what we found out is that we were removing 44 gophers per day with both trapping and aluminum phosphide quite consistent actually there. And the PERC machine, we were actually removing 47 gophers per day. So slightly more, even though the efficacy was quite a bit less, the reason why is because we could treat multiple burrow systems, we could move through an area more rapidly. So, that gets to kind of one of the advantages of this particular device. So, once we had that number of gophers removed per day, then we could go back and relate the costs of that to come up with a daily cost per pocket gopher removed. And this is where we get into the amortizing of costs again. With aluminum phosphide no amortizing needed it's a flat rate.
For trapping there is--you have to buy the traps initially and then you have to replace traps periodically throughout time as well. So, you do have a little bit of cost. So, some amortizing involved there. For the PERC machine same thing, you know, the cost is going to be really high when you initially purchased the machine, but that cost is going to go down over time. So, what did we find out? Well, we found out initially that, aluminum phosphide of course was the cheapest because you had no additional materials to buy, but very quickly trapping drop below that after about 20 and 25 days. So, trapping is a very cost-effective approach when it comes to managing gophers. PERC machine, it took a while, but eventually the PERC machine got to the point where it dropped below aluminum phosphide and it took less time for gophers than it did for ground squirrels incidentally.
So, certainly there be some utility there. I always like to point out it never does drop below trapping. Trapping sometimes gets a bad rap for being labor intensive, but it's important to remember number one, that trapping is highly efficacious. We see 90 to 94% removal rates oftentimes with trapping. So, it works really well. And when you get good at trapping, you can actually set a lot of traps pretty quickly. So, trapping is a pretty cost-effective tool. But the PERC machine definitely can be a more cost effective; obviously, the longer you use it as well.
Yes. Yeah. I always use the Gophernator. We've tested several different kinds of traps out there. The Gophernator has consistently proven to be the most effective of the traps that we looked at. So, that is the one that I prefer. And these values would change if we utilized different traps.
If you utilize a less effective trap, it's not going to be quite as cost effective for you, which gets me to this particular caveat here, this data, the reason you don't see a lot of these costs assessments is because it varies tremendously from site to site. Who's applying, who's doing the trapping, who's applying the fumigant, etc. So, there's going to be a lot of caveats to this. This won't be the same situation in every location. I have trapped areas where I can put out a trap set in two minutes. I've trapped in areas where it takes me 10 minutes to put a trap set out because it's really dry or rocky or something along those lines and in those settings trappings not going to be very cost effective to give me a lot of other more cost effective tools. So, keep that in mind. In this particular scenario, this is how it, it showed up for us, but it does, I think provide a good window into the cost effectiveness of this device.
It can be relatively cost effective if you plan on using it for an extended period of time. Your question.
Was Gopher Hawk one of the traps you evaluated?
We have never tested the Gopher Hawk and I need to, because I've pretty much every one of these presentations I give, somebody asked me about the Gopher Hawk. There are lots of people using the Gopher Hawk right now and most of the feedback I get is very positive. My general inclination is that it's not going to be as efficacious as the Gophernator, but that it will be quicker and easier to set. And so how does that combination compare to the overall utility of the Gophernator? That's what I'm really interested in. But I haven't done it yet, too many things, too little time, but it's a great question.
Yeah. Well I forget what value we used. I think it was $10 or $12 an hour or something along those lines. Yeah. We use the same per hour rate for all the different strategies, yeah.
Right. So, in that case, we had to go back, that's where we had to use equations to calculate it because we don't know exactly what that number was. What we did is we more or less used our overall efficacy rate. What we did do is count the number of applications we had per day. So, we took that efficacy related that to the number of burrow systems we treated to come up with an overall number of gophers that we likely removed per day. But we don't have an exact number of that. No.
Great question. So, how often do we get incidental captures in gopher traps? Almost never outside of moles. We will catch moles occasionally. Like if I put out, this is just off the top of my head, but if I put out a hundred trap sets for gophers we might catch--and it depends on the density of moles in an area--sometimes there aren't any moles so we don't catch any. But if there are moles and area, we might catch two moles per hundred traps sets maybe somewhere along those lines. As far as other non targets, we caught one gopher snake out of several thousand trap nights and that's it. That's the only other non target we've ever caught. And the gopher snake, we just let all the trap and he went away.
How often did you check the trap?
And have you ever done the trapping in an area where [inaudible]?
No. We tend to avoid those for specific reasons. Yeah. Right. So, that's always the limitation. Whenever you're dealing with endangered species, you have to figure out what the endangered species are and what might potentially impact them. Particularly relevant for burrow fumigants because there are a variety of species that might be living in burrow systems. It's more so for ground squirrels than for gophers. But it is I guess possible, that you could impact them in some gopher burrow systems too. But far more likely in ground squirrel burrows systems. So yeah, there are plenty of situations in which you would not use fumigants, if you're dealing with a lot of those endangered species in a given area. Yeah. There are a lot of people that actually prefer to use--it seems counterproductive--but there are a lot of people that advocate actually for the use of rodenticides in areas where you have endangered species in those burrow systems because it's far safer to use than the burrow fumigants when it comes to those non target endangered species, yeah.
So when it comes to endangered species, is it the ground squirrel versus a bird of prey?
Right? So, the endangered species, if we're talking about blunt nose leopard lizards, red legged frogs, California Tiger Salamanders, things like that, they're not going to be feeding on the bait. And they're not going to be feeding on dead ground squirrels. So, they're not going to come into contact with that product. But if you're putting the fumigant into a burrow system where they are there, then it's going to kill them just as quickly as it would a ground squirrel.
And what kind of trap was it where the gopher snake was caught? Do you remember?
It was either a Macabee or a Gophernator. I want to say it was a Macabee, but I'm not.
You said it was alive though, right. You said it just crawled away, right?
Yeah. Well he was caught in the trap. We went up there. And we said, "Uh, oh!" we let them out and he's just-- yeah, he didn't seem hurt in the least. So, yeah.
I'm not saying it would always be that way, but in this case, yeah, he's completely healthy. Now, the only other study I've ever seen about looking at non target capture rates was more in--gosh, where was it? Washington maybe? And they had chipmunks around and so they did, I think they were laid on a thousand, a thousand trap night effort and they had about three or four chipmunks that they might catch per thousand trap nights. So again, very low, but it's possible.
Yeah, I agree. I understand. Yeah. That's a potential at least a potential hurdle there.
I caught a gopher snake in a black box, and it was safely released as well.
Oh, good. So, I would be more concerned there because there it's a little bit more powerful of a snap.
It had a girdled wire that goes up. It's called a Get Gopher, and so it was doubled-up.
Okay. Coming towards the end here. So, is the use of carbon monoxide and carbon dioxide, is it a useful tool? Well, we find that it's highly efficacious for ground squirrels, at least the PERC machine was highly efficacious for ground squirrels. The Eliminator based on the other independent study that was done seems to suggest that it's pretty effective for ground squirrels as well. We found it to be moderately effective for pocket gophers. I definitely think it has some utility. It's not as efficacious as some other tools, but in areas where you don't have many other options, it's certainly is a tool that I think is worth considering. And it may not be as cost effective as some other approaches. I understand that. But the cost does decline over time, the more you use it. And again, it gets back to that idea of do you have other practical options to use? If you do that, maybe you use those other options a little bit more extensively, but if you don't, then this becomes a tool that could be a good option for you. So, with that. That's my spiel for today, but I'm happy to take more questions.