OBAMA ~ Mustang poster © Lise Stampfli 2009
Cross-posted from Hippies 4 Horses by Afroditi Katsikis
This is the text of the meeting of the Wild Horse and Burro Advisory Board meeting held on September 9, 2013 in Arlington, Virginia. This text was copied directly from the captioned text of the live-streaming meeting– no edits or corrections – only some spacing to make it easier to read. I can not assure you that it is complete as per the meeting – it is as complete as the captioning was on live streaming.]
[Joan Gullifoyle starts the meeting]
>> Okay, hi, everybody. We’re going to get started in two minutes. So, if you would take your seats and finish up your conferences. I can’t couldn’t see because I can’t see that side of the room. But Carol Lanne of the National Research Council National Academy of Sciences is here and she was very involved in the coordination of this report. I wonder if she would take a moment to explain in digs to the 11 questions that the BLM asked of the NAS, what the — what the report did and didn’t cover intensely just to help it be more clear why some things may be in and some things may not be in and what you’re leaving it to us to kind of do with the report if you wouldn’t mind.
>> Sure. Thank you, again for making the report your focus of this meeting. My name is Cara. I’m the study director for this particular project. And I’m a program officer at the National Research Council.
As you’ll find had your report on page 2 and 3 in the summary and then again on page 16 and 17, that’s a statement of tasks that the BLM and NAS agreed that the committee would look at.
Following that there’s a section in the report called bounds of the study which goes through what we were asked to look at and what we weren’t asked to look at. As you’re all aware there are many issues that are not related to science but national research committees are commissioned to look at science-based questions so that lends itself to the nature of the questions that are part of the statement of task which have to do with population estimates, range land estimates. Population growth. Genetic diversity population control. Things outside the bounds of science supp as how many animals should be on the range — because that’s a policy question, not a science question. Forage can tell you how much forage, how animals may use the forage, how different animals may use the forage but how many animals you’re going to have out there and what kind of animals they’re going to — for instance livestock and wildlife or some of all. That’s a question for policy makessers to make. So the purpose of the report in answering the science question is they can inform the policy conditions. That’s the role of BLM. Not the committee.
>> And Kara, if you don’t mind just for clarification, what BLM asked the NAS to do was look at these 11 questions about the science of the animals on the range. But not to look at perhaps the multi use nature of the rest of the agency for example. Is that right?
>> KARA LANEY: Yes, things like whether the law could be changed, whether different laws perhaps conflict with the Wild Horse and Burro should be changed, whether the allocations can be changed. Those are policy conditions that the policy was not asked to look for?
>> JOAN GUILFOYLE: And the logistical political educations that were asked for that were science based you’re leaving up it up to the receiving agency to determine the feasibility of some of it.
>> KARA: Correct. So the budget associated with recommended actions was not part of the committee’s purview. As you’ll note in the report, we do find that — we do go so far as to say an option will be expensive such as continuing to move horses to long-term holding will be expensive and the committee thought that its recommendations would be less expensive in the long run. You about we don’t go through and put a financial — attach a number to those actions or to the actions of gathering animals, implementing fertility control, anything of that nature.
>> JOAN GUILFOYLE: Boyd, just one more thing if I could add. The NAS, if I can say for Kara just for a moment, was concerned just as we were that there were a lot of interpretations about the report immediately after it was filed and to look at how we could correct that or they would correct that. They did do a posting on the Web site and I don’t know if you’re going to be here, Kara but I’d like that to be part of what we share with everybody.
>> Sure, I plan to be here the whole time.
>> JOAN GUILFOYLE: So we can go over that briefly now or wait until public comment period or Wednesday morning. It doesn’t matter. But I want to make sure that you all hear what they felt the media had misunderstood about the report and to be clear about what they said.
>> DR. BOYD SPRATLING: Kara, just so you know, we’re going to take latitude as a board to ask questions while we have experts in the room. We fully understand that a lot of the questions we ask were not part of the boundaries of the study and report. While we have people here that understand the dynamics out here, we’d like to ask questions to help us from our recommendations to the BLM.
>> Please make use of our expertise, they’re helpful to us and I hope they’ll be helpful to you, too.
>> DR. BOYD SPRATLING: Thank you. Next I’d like to introduce Dr. Robert Garrott. He’s a faculty member of the Department of Ecology at Montana State University.
>> ROBERT GARROTT: Thatch. I have two back to back talks one dealing wees mated population size and growth rates and then I’ll give another one on chapter 6 as well.
So as everybody can imagine, how many horse there are out there and how fast they grow is basic fundamental actions for the problem might take. So our job in this chapter was to look at those things and the objectives within that chapter was to review the the method used to inventory horses by the BLM and provide potential recommendations for improving the methods. And thirdly to review the data available to estimate growth rates. Typical growth rates of course on western range lands.
BLM spends about 1% of the wild horse and burro budget. Inventories horses, Marx sure the animals are accounted, HMA herd management area periodically and those counts are then used as your foundational knowledge for population management. Key attributes of any scientifically rigorous are good survey method. Scientific standpoint is that the methodologies be rigorous and standardized, that there be a statistical basis for how that’s done. That they’re consistently applied, they’re well documented and that the data that comes from these are complete, organized, and accessible. So that’s sort of the gold standard for what we’re looking for in a scientific inventory program for wildlife.
Our expectations before we actually looked at any of the BLM databased on our understanding of how the numbers will be generated and this partly comes from my experience in the 1980s when I worked on this issue by population dynamics of horses and potential of contraceptive control on horses in the 1980s and I worked with all the BLM offices was that there be a periodic count. So someone from the Bureau of Land Management most most likely wind up in a helicopter or airplane and flew through the herd management area and counted all the horses they could see. That count could be reported as a population estimate which you see this column here in this fictitious table that’s empty right now or that count could be modified to come up with a population estimate. If you think you counted them all, in other words, you had a perfect census of the heard management area, you just translate the number you counted into that population estimate.
But in general what we do know about counting large mammals and many, many places is that we don’t count them all. There’s a bias, what proportion you counted can be use if you have an estimate of that or even ball park figure, you can take and modify your count for the proportion you think you actually counted or the proportion you missed and come up with a population estimate. For example if we couldn’ted 422 animals and we thought we counted 80% of them, if you divided 422 by .8, you getten an estimate of 527 animals on that heard management area you’ve accounted for approximating what you think you might have missed.
But we also know that we don’t have the budget or the agency doesn’t have the budgets to count these populations every year. So, if you need a population every year. And you’re not going to count those years and you have some way of projecting that population from one year when you did do the count to the next years when you don’t do a count. And in general the expectation is you’re going to multiply your population estimate in one year by what you think is a growth rate of that population over the next year.
New England this case, this example, if think that the population is growing at 20% annually, we multiply 527 by 1.2 and we get an estimate the next year. And next year, 2003, there’s no count, you do the same thing again. Get a pop ration estimate. 2004, you get a count. You do whatever you’re going to do to that count to turn that into a population estimate and that’s — with the expectation of what was being done with the Bureau of Land Management. Then of course for national statistics if you do that for herd management areas every year and you aggregate population estimates for haul the herd management area, you get statistic how many horses you think are on the western range land throughout the west. So that was our expectation.
And to see if that’s what was actually being done, the NRC committee requested the BLM provide us records from 2000 to 2011 for all herd management area. The BLM was –’s response was that there was no — excuse me. No centralized database. The data was first among field office thought that request wasn’t manageable for what they asked it to do, they thought what would be more manageable would be if we requested records from agencies and suggested a maximum of 40.
And so what we did is the committee selected the 40. HMAs that requested data for and these are the distributions of the sample of HMAs that we received data from BLM versus the number of HMAs based on criteria that were available to be sampled. So we got records from 40HMAs represented there across those states based on the sample we requested.
And this is an example of what we got back. We provided BLM the national office a standardized table so we could get the data back in the same way. And I’m going to spend a little bit of time with this to point out some attributes of this. So this — I’d say, is a typical record for one of the herds we saw. And you request see that there’s attributes across the columns and there’s data filled in and there’s places where there aren’t any data. So those are the actual population counts. And the first thing you can see is that they’re irregular as far as when they were conducted. So sometimes we had two counts. Back to back and other times we had a year in between and sometimes in this case, a couple years in between. So there’s some inconsistency on how frequently this herd counted.
There’s a real inconsistency on when they were counted. And this is important because there’s a birth pulse where the population increases because of foaling and then throughout the rest of the year, there’s attrition, animals are being lost. If you count the animals at different times, you’re counting for a different amount of the seasonal mortality that occurs. And it makes the data less comparable from year-to-year.
So there’s inconsistency in these records in timing of surveys. And here you can see that there’s inconsistencies when the survey platform. Usually a helicopter was used. And then one year a fixed wing airplane was used probably because of logistics or perhaps budget. Fixed wings are much cheaper than helicopters. But the proportion of animals you can detect different survey platforms to be very different. So by changing your survey platforms from year-to-year, you’re probably adding additional variability to the count data that has nothing to do with what the population is doing. It’s due to your changes in the methodology you’re using to count them.
You can also see here that there’s also incomplete counts. Here’s that year that the fixed wing was used, only 70% of the area was surveyed. So that that adds a little bit of problem to interpreting those data as well. Now, if you look at the relationship between the population count and the reported population estimate. You see there’s a difference in this. There’s a first record. 190 were counted but population estimate was 164. You look over there at the last column on the right, the adjustment to the count was filled in as none.
But it — but the numbers are reported as being different. We’re not quite sure why those numbers were different there could be many reasons but we don’t know why. If we go down this column and look at how that number changed between counts and the population estimate each year, you see this year, the population estimate was a little lower than the count. Next time that incomplete count was 60, for some reason it was a really low count. But the population estimate — next year the population estimate was exactly the same. The next year it was counted, a little bit higher than the count. Population estimate was a bit lower. Next year is much lower. Next year little bit lower. Next year could be accounted for if there’s removal between population count and population estimate and that was accounted for.
We also had data on all the removals so we had the ability to cross reference these data to see if some of the discrepancies especially if they’re lower, sometimes that was the case. And then you had the years that there were no counts and the population was projected for those years as well. And we could find real consistencies if we adjusted the math just to see if there was a multiplier effect for population growth rate. If there was, it was very inconsistent from one projection to the next on the years that there weren’t counts. Here’s a different record that recommends another HMA that represents the best record we had at the 40. You can see that everything is consistent. Consistent use of both vehicles and horses. So these are ground counts, consistent time of the year, area was completely covered. Population counts were believed to be a census and they were always reported as population estimate.
Herd happens to be one that the USGS was conducting research project on supported by the BLM and so this might be a reflection of a research activity this herd is very much like the prior herd where the horses are all known individually by color patterns, there’s a lot of people to keep track of every horse. So this is an example of a small isolated herd. This would be represented of the horse record we received where there’s very little data filled in. There’s wide gaps, inconsistency where they’re counted and no population estimates filled in at all. We can just assume that the count was projected as population estimates since nothing else was provided in this table.
This gives you a representation of the types of data we received from the Bureau of Land Management from their inventory program. The other type of data you get is aggregated data which is reported on the BLM Web site that gives you an idea of the — excuse me, trajectory of the population range wide population throughout the west. Each of the data that have been reported on the Web site. This is important because it’s interpreted by public administrators. Gauge success of the program. It’s used in formal government review programs from the government accounting office reviews. And foundational data for planning and budge teary decisions that go to the Congress as well.
Given some of the data we saw in the field offices we weren’t quite sure of the national number. We started a conversation with Bureau of Land Management national office asking for an explanation how those national statistics came about. We were provided no documentation linking the national statistic to the field office. We compared the field office data from the sample of 40 HMAs and looked at what was reported on the Web site for those HMAs that were aggregate for national statistic. So Web site reports the sum but it also reports the number of population estimate for each HMA. I’m sorry, I had surgery just a little while ago on my throat.
And so when we did that, we found quite a few discrepancies between the field office data provided to us in given years and what was reported on the Web site. And we received no explanation of those discrepancies. So we just link — we can’t adequately link the field data to the national statistics.
So the committee conclusion regarding quite a few methodological flaws, inconsistent methods. It was also noted very often and with the public gave us testimony about movement of horses among HMAs. Which can confound at the HMA level that horsees are freely moving back and forth and adds variability to interpreting data. These are just straight counts.
Go up in a plane or helicopter and count all the ap malls you can see. So there’s no it at that time tickal method so there’s no proportion of animals detected which can be very substantial. The proportion that are missed. That’s giving a statistical range in what’s a plausible value given the data you collected and certainly inadequate recordkeeping and database management.
So we concluded that BLMs current herd inventory procedures don’t meet the modern standards management applied for most other systems where we’re required to inventory populations that we manage. Given how the data were collected and reported, we we concluded that the population estimates that are provided are likely substantial underestimates simply because we know we don’t count them all when we go up there and there wasn’t in most prop Asian estimates counts weren’t reported directly and if you didn’t count them all, it would suggest that the population estimates that are reported are underestimates of the number of animals actually on the range.
We also noted that this is the exact same conclusions that were made 30 years ago by the NRC committee that was in place when I was doing my Ph.D. in the 1980s and so this has been and this seems to not have changed since the program began. We also noticed there are attempts to improve the inventory program.
2010 wild horse burr and burro management handbook is published a rigorous set of guidelines for survey techniques and these are an excellent set of guidelines that mimics what I dictated as what would be ideal attributes there at the beginning of my presentation. They’ve also been working hard to aggregate HMAs where there’s a believe that horses are freely moving among HMAs and to essentially come up with more reasonable biological units to conduct surveys over which are called HMA complexes. So, if there’s no fences or fences are permeable between heard management areas, aggregate them together. Census and manage that as one population so it’s more interpretable data. That’s an improvement or could be an improvement if it it’s implemented.
And finally, BLM has had a partnership with USGS for about a decade to develop and test statistic rigorous survey methods. There’s a lot to be had from that 10 years as far as developing methodologies and horses can be counted well and scientifically rigorous. You can estimate detection probabilities and do a better job in that decade of collaboration certainly gives us some good science.
So our recommendations for improving population monitoring is that those two things that have been initiated, those guidelines from the 2010 handbook and the HMA complex initiative that those things actually be implemented well and consistently across west and evaluated on a routine basis. We also suggest that BLM should consider more intensive monitoring for what we call sentinel herds. So I’ll relate a little bit more to sentinel herds and why this is important, why we think this might be important in the presentation on the next chapter. But this is the idea that on some of your heards, a sample of your heards throughout the west that represent a diversity of ecological settings where BLM manages horses, that survey and inventory work should be done almost an annual basis in order to better understand population of horses.
We recognize there’s a budge teary constraint that’s firing that most HMAs only be inventories every two, three, four years, but in order to get the foundational knowledge like population dynamics, at least a sample should be monitored relatively routinely. Probably annually, to provide good data that can then feed into population management decisions and models that I’ll talk about.
We also recommend improved recordkeeping and development of a standardized and comprehensive database. And that all of this, inventory procedures. And data be made readily available to the public. We heard from a lot of public constituents that they don’t trust the numbers, don’t know where they come from and we think that that causes a lot of mistrust between many public groups that are concerned horse and burro management and the agency that’s responsible for the management.
Dealing with the second subject, population growth rates, our work primarily was limited to looking into literature review because there hasn’t been a lot of data available to estimate growth rates. So we looked at the papers that were published in the literature to estimate growth rates. We did conduct one novel analysis that provides additional insight and we looked at the age structure of about 168,000 horses that had been removed from public lands in the west. To try to get additional insight.
Essentially what we did is for each year, those horses are all age removed, that’s a lot of horses each year. So what we could develop is a young of the year to adult ratio is. And this is what those data look like. So this is sort of a moving window average of the young of the year versus an adult ratio for the horses removed from the range each year.
And you can see that generally between 20 and 25 young of the year say per hundred hundred adult horses so this is an index of population growth rate using those age data. We know that would be biased to growth rates because horses are moved to the range in order for t for it to be indicative of the actual growth rate, all the horses would have to be removed before the birth pulse. You had all the an halls that were going to die for the rest of the year up to the next birth pulse and I’ded y’allly that’s when you’d use these ratios since they’re throughout many more months, it’s providing a bit of an overestimate of population growth rate. But you can see where those numbers lie. 0 so our conclusion is while growth rates certainly virginiay from one herd to the next and within a heard — vary from one herd to the next both the population and age structure data from the horses removed is consistent with the idea that typical growth rates are probably in order of 15-20% annually. What’s that mean?
This is a graphic, a table, BLM estimates that there are 3,000 horses on public range lands in the west this year. If we want to project the number, say horses aren’t managed based on the growth rate you multiply that 33,000 by 1.2. And these are the numbers you get from that. So 20% growth rate would lead to a population doubling every four years if they weren’t actively managed and contribute willing in six years.
If you look at the same data for 15% population growth rate, if left unmanaged, horses would do you believe every five years. And triple — do you believe every five years and triple every 8 years until they became food and water limited like we heard about from Mike in a previous presentation. But that growth would probably go for quite a while when we start seeing that food and water limitation throughout the west.
So what’s that mean, these sort of numbers mean as far as BLM’s real dilemma and that is trying to manage the annual increment of horses so the population gets stabilized. So, if you multiply, this would be the annual increments for that 33,000 horses on the range that would accrue over one year, this current population if the populations were growing at 15 and 20% annually. You can see 6600 horses would be added to the population I’ll point out that for 10 years BLM has been removing an average of 8700 horses a year from the western range lands. Considerably higher than that annual increment at 20%.
And the national statistics would suggest that the population over that 10 years is approximately about the same. If the population is growing at 30% the BLM could remove an average of 8600 horses, I think that’s additional evidence that there’s more horses out there than the reported number. And it also provides evidence that these growth rates are realistic given that the off take of horses and the removal program.
So what would that mean if we looked at that annual increment at the different population levels. This would be the number of horses that those different population leveled. You’d have to remove from the range land just to keep the population in any one of those years stable. We know we can only adopt anywhere between 2 to 4,000 maximum. That’s the problem. And so you can see that there’s two things that are going to affect the annual increment that has to be removed. The annual population growth rate and the number of horses you have on the range.
So, if the ultimate goal would be horse management in the west is to only have to remove the horses that you can readily adopt 0 so you can get rid of long-term and even short-term folding facilities, you have to get the annual increment down to between 2 and 4,000 horses and there’s only two mechanisms to do that. And that would be to reduce the population growth rate which we have the NRC committee recommended at least three or four different fertility intervention technologies that could be used and/or you’d have to limit the number of horses on the range so that base population that that growth rate is acting on can meet those management objectives of 204,000 horses to be adopted. — 2-to 4,000 horses.
So in summary, we think the horse inventory procedures are not scientifically rigorous. That improvements to those inventory procedures have been initiated but we don’t know the extent to which actually been manipulated. Our implemented, excuse me. And whether or not that’s range wide throughout the west or not.
We definitely think that recordkeeping and database management has to be substantially improved. There’s no clear linkage between the national statistics and field offices or at least it wasn’t demonstrated to the committee. I’m sure there is a linkage but we don’t know what that is or we we couldn’t cover that and horse populations are growing at 15-20% annually. And with that, entertain questions if we have time.
>> Thank you very much for that presentation. Do we have any questions from the board. (off mic).
>> Have you done — in looking at nonlethal methods of slowing the growth rate, have — with what — what you’ve learned so far, do you feel that there is an opportunity to zero the growth rate based on the current population sizes?
>> ROBERT GARROTT: So the question — I don’t think the mic was working the question is do we think there’s a possibility to stabilize the populations using only –
>> Correct with the current based population?
>> ROBERT GARROTT: That wasn’t part of the charge of the NRC committee. I can tell you that there are a fair number of papers that were population models using horse data have been built and then what might be considered realistic fertility interventions with the tools available today and what might be viewed adds realistic treatment levels have been applied and in general, those modeling experiments would suggest that fertility control can help rethe growth rate but it will probably be very — reduce the growth rate but it will probably be difficult to stabilize the population useility control alone.
The fertility control is dependent on the number of the horses, the population of the population that can be treated. You can’t tread them all or if they do, it can be very expensive or difficult. And so it can help the problem but fertility control at least in the current forms we have probably are not going to — is not going to be able to essentially stabilize the population at whatever level.
So it can help. It can help substantially.
>> One of the tools that can be used.
>> ROBERT GARROTT: One of the tools, yes.
>> Thank you, again, appreciate that information and well-presented. I’ve got a couple of questions. So back to the estimating of the population size. And where you weren’t, I have my note here, did you question the local offices. So my understanding is you had to go to the local offices to get the data that you did for each one of those 40, is that correct?
>> ROBERT GARROTT: Not quite. The NRC communicated only with the folks at the national office. So the national — when we requested the data from the national office, the larger data request, the national office asked us if we would make a more modest request. We made a request to the national office. And I think they made a request to the field offices and then the data came through back to us through the national office. We didn’t have communications with the field offices directly.
>> All right. Thank you for that clarification. So off you’ve not had the opportunity to have the conversations with the local staff at all in any of the BLM offices?
>> ROBERT GARROTT: Not as part of the NRC committee.
>> Okay. .
>> On the new ways of counting that have been put in the policy book, there’s two, I can’t remember what they’re called. The handbook, yes. My question is are you familiar or have you seen them be what I guess I would refer to as ground troops or are they just models? I guess what I mean by that is for instance in the little book cliff because we do know how many horse there by name and picture. Have we flown that and done this process to verify that we are accurate?
>> That was one of the areas that USGS worked in. That they did do one of those survey methods which is called more creek capture where essentially that — every animal’s ID’d by his particular colors and patterns. They’re all individually marked. They’re intensively surveyed and known you actually very seldom do actually know the truth. So they use this herd because they did know the truth and then they applied a March creek capture technique where they didn’t use the known identities of those horses but you fly once and you photograph bands of horses and you essentially mark those bands you saw by the coat colors of that aggregation of horses.
Then you go out and do a second flight and now you’re considering those groups being marked groups, you know them. You saw them in the first light. And you go out a second time and you fly and you see unique groups that you saw the second time that you didn’t see the first time. You see the proportion of the marked groups that you saw in the first slide. And that can — stat thickly adjusted — statistically adjusted to allow you to estimate for the proportion missed.
So essentially you have your first flight identifies animals you know are out there. Groups you know are out there. Second time you don’t see them all and you see new ones so that provides you a way of estimating the proportion missed where you don’t have to know all the horses from the ground so you can do this on a — on a herd where you don’t have those individual IDs for all the animals. It does require, though, it’s hard to believe that this technique would be used for population these horses. It’s a methodology used for relatively small eyes isolated population where it’s realistic to do that and it take quite a bit of manpower to go through those photographs and identify them all. So what USGS did is identified a suite of techniques and they evaluate several more that didn’t work out very well.
And it would be that you’re not going to use — you probably wouldn’t be using this same methodology for every herd management unit. You have a suite of scientifically rigorous methods that were matched to the ecological conditions and the survey conditions on the various ranges.
>> Thank you.
>> DR. BOYD SPRATLING: Dr. Bray.
>> Dr. Bray: Dr. Garrott? Robert Bray. Clearly you and your colleagues on the committee have provided a comprehensive review of the literature so thank you very much for that. You reference that the field data was — could not be linked to the national statistics that were imported. Was there any pattern in those differences, less, more, highly variable. Any numbers to say they were consistently X percentage? Differences.
>> The only thing we’d have there is the population estimates reported for the 40 — the sample 400 HMAs that we were given and compare that against what was on the Web site for those herd management units. And for those where we had the field population — field office population estimates and we could compare with what was on the national Web site there was no consistency. Less or more?
>> I would also offer that of those 40 HMAs, I think something — I have to look back at the report. I can’t quite remember the figure but I think we only had about 50-60% of those population estimates filled in. From the field offices. But there were population estimates filled in in all the national statistic.
>> Was there a subsequent requests when you did not receive one the first time? Did you have a delivery request?
>> ROBERT GARROTT: There was about six months of communications back and forth to try to understand.
>> Dr. Bray: Is there any reason they were ignored or not responded to.
>> ROBERT GARROTT: They were always responded to. We always gout responses and I think that the records of the committee would have all the email responses went back and forth about that except for a couple conference telephone calls that weren’t recorded.
>> And finally with the 40 HMAs that you requested numbers from were they randomly selected or were they identified by the national law office as to what was going to be provided.
>> ROBERT GARROTT: No, the national office didn’t select that. The committee selected that.
>> Was that random or how did you go about making those 40?
>> It was a systematic examine and let me explain that a minute. We took the most recent population estimate for each HHMA, we ordered based on population size, since we could only get 40, we decided we didn’t want to burn up our sample of 40 by getting records for an HMA where there’s only 12 horses or 30 horses, we wanted to have something that represented both a range of horse sizes but but to get the best information we could from those 40. The present population had to be at least 40 or 50 animals. It couldn’t be a mix of burros and horses because we wouldn’t know how to split up that number between those two. So it was only horse only HMAs and then when we had that listing, then we took every third. So — when that list — we got a systematic sample across the range of horse sizes. That took us up to about 336 and then we added 4 in the 80s we he had population data that weren’t on that list that would give us more data that could reflect population growth rates to bring it up to 40 and that’s how it?
>> ROBERT BRAY: And one finally — my voice normally carries so I don’t worry about a microphone.
One final question, when you look at that pattern of differences between field data versus national numbers, can you give me a sense of high and low and how they varied? They were off by 4% or –
>> ROBERT GARROTT: All I can say is sometimes they were right on the money. It was exact same we got in the field office. Sometimes they might minor differences on the order of physician horses but it wasn’t unfrequent, infrequent to have differences of hundreds of horses. And the proportion would depend on the herd. We looked for patterns. We looked for patterns and could not find consistent patterns. So I think the NRC committee report we said we think that the national estimates are based on probably many hundreds of somewhat subjective independent judgments because there were certainly judgments being made at the field offices when they reported population estimates. And there must have been judgments being made at the national office as well after they got the field data.
>> ROBERT BRAY: I probably know the answer to this. But 15-20% foaling rate, do you think that’s a real number?
>> That wouldn’t be the foaling rate, it would be population growth rate.
>> ROBERT BRAY: I’m sorry, do you think that’s a real number.
>> ROBERT GARROTT: I’m not sure what you mean by that.
>> ROBERT BRAY: Do you think it could be substantially higher?
>> ROBERT GARROTT: Probably not. It’s plausible based on the biology of the animals, but probably not much higher. Some of the literature has reported population growth rates up to 28%. And the way that’s.
>> DON: I think in all of those records it’s where you have a good sequence of population counts. Say, 8, 10 counts in consecutive years and you can look at the trend of those counts and estimated a growth rate from that and that particular methodology has generated some estimates of population growth that exceeds 20%, up to about 28% there’s confidence limits on those and that’s when those higher estimates would cover 20%.
>> That model wouldn’t be based on accurate counts of animals.
>> It’s .
>> You how do you define an accurate count if you don’t know truth.
>> You could have some variability in what proportion you count every year but, if you had consistent methodology, and you counted those populations over over a number of years, you could statistically estimate the growth rate even if you don’t know the proportion you counted. And you get a legitimate and scientifically rigorous estimates of growth rate without knowing truth. How many horses are out there or any wildlife in our populations other than those few that are tracked by individual animals and they’re all named and you’ve got 20 people growing up out there that loved him and watch them and keep an eye op them for you?
>> ROBERT BRAY: Thanks again.
>> ROBERT GARROTT: Yep.
>> I’ve got a couple questions on the growth rate, do you have a percentage of it’s interesting, I spent my entire career working, one of the places I work is Yellowstone National Park and there’s more science on the demography of one out population in Yellowstone National Park than this entire species on the western range lands and indeed there’s been very little science done and most of it was done in the late 70s and 80s on population demography, growth rates, foaling rates, serious signs to understand horse vital rates, survival reproduction age first reproduction pregnancy rates.
And so there isn’t much science there and that’s the idea of sent until populations could help us get a little bit more of that. But certainly pregnancy rates at least 50-60% based on — 50-60% pregnancy rates based again on research done way back in the 70s and 80s, where a lot of horses were bred and certainly levels were assayed for horses being removed from the range land and part of a big research project that I was part of there in the 80s. So the foaling rates, the pregnancy rates as much as we can tell in the foaling rates would certainly support the idea that populations could routinely be growing at 20%. (off mic).
>> That would be more valuable than the actual growth rate of the herd I think as far as knowing population growth expression. Am I incorrect in thinking that way?
>> ROBERT GARROTT: So you don’t know which animals are pregnant or which animals are fertile most likely when you’d be treated them. So you’re going to — in a practical standpoint, you’d be treating at least Mary oriented contraception. You could be — wouldn’t be able to carefully target which animals were probably treated. In order to do any effective management with contraception and I’ll touch on that in the next presentation, you certainly have to have — or I would think you’d want to have some model of population dynamics for the horse herd that includes pregnancy rates. As well as foal survival.
>> TIM HARVEY: That’s where I’m going, I’m trying to figure out how many Maries you would optimally treat to get that rate you’re trying to get earlier to achieve the number of growth rate you were talking about that would be sustainable.
>> It would depend on the demography of the herd. So even though our conclusion is that typically herds in the west are growing on average of 15-20%. There are probably herds that are growing much less than that.
>> TIM HARVEY: I’m grasping for is there a number we need to treat 15% of the mares, 40%. The number that gets treated is quite low. So what I’m trying to get my mind around is mares need to be treated 0 on average. Can you comment or can you throw a number out there how many would have to be gathered and treated in order to affect some of the changes that we’re looking to do?
>> ROBERT GARROTT: So effect some — so — there have been a number of population modeling studies looking at just that question. If your target is the reduced growth rates, and the mare that you stop from having a foal for a year or two is helping to contribute to that. If you’re looking for a proportional decrease, it depends on what your state agoal is. If it’s to reduce the growth rate by athe least half, I think all the studies that have been published thus far with limited demographic data on horses it would suggest that at a minimum for mare oriented couldn’t Secretaries only you’d have to be treat — couldn’t sent only you’d have to be treating 20% of the mare.
Chemical vasectomy could be used, no one has incorporated any modeling that experiments where both mare and stallion contraceptive tools were used in combination. The bottom line is that to have a noticeable and a measurable effect that you could measure with good population inventory techniques, you’d have to be treating at least 30-50% of the annuals, of the animals and you’d have to repeatedly do that at least for the mare oriented an animals that were available.
>> Can I follow up on that, you’re saying you’d need to treat them. Is that accounting for the fact that only a certain percentage are going to be effective in contraception. Are you saying that 30-50% have to be couldn’t sented or treated?
>> ROBERT GARROTT: We’re getting way beyond the NRC report. The NRC didn’t do any modeling of that. So I’m speaking partly from the modeling that’s been done in the past of which I was part of when I was involved in the wild horse research in the past. I think that the NRC committee did strongly recommend that fertility control, there’s been 30 years of research on fertility control specifically targeted horses. That the problem of excess horses as defined by appropriate management levels that BLM has now is a real issue I think you can see by the end of that presentation that reducing growth rates can contribute to helping BLM solve the problem.
How it can contribute, how much it can provide, this would be a management experiment because nobody knows. But we do know there are multiple pools that can inhibits reproduction effective with side effects in the context of behavior in ways that were viewed to be acceptable. That could be applied. You about it’s not something that we’d recommend that BLM be able to say that for the next 10 years, we’re going to increment the number of horses treated with TZP or something by a thousand. It needs to be done if it was going to be credible, it needs to be done as science and as an experiment because it’s very uncertain how much of an effect it can have. But we’re very comfortable with the fact that it could have an effect. It could have a measurable effect.
>> Did you have a follow-up question?
>> TIM HARVEY: I’m just thinking numbers. I’m a numbers guy and I’m just listening to within 5-20% growth rate wondering what we have to do to get that growth rate down to something that can be handled by the adoption program. So looking at the growth rate and how does that shake out from foals in the ground and natural mortality westbound the herd? And you know, because that’s going to knock that number down a little bit. I think that again we’re outside the committee. Commit he it’s work.
But there was — some work done outside of the committee. And it’s a pretty easy math exercise if you look at that last table. If you applied if you aenough horses on the range for horses, I think the upper level for appropriate management is something like 23 or 24,000 horses on the range land. If you had that many horses on the range land and you reduce the growth rate by 50%, so dropping it down to 710%, you’d have annual — 7-10%, you’d have annual inyes 3,000 horses that could be adopted equival