2:10 - 2:45 pm
Ungulate Population Trends &
Winter Wildlife Monitoring Update
P.J. White, Yellowstone Center for Resources

Transcript

Female Voice: And we have one more?  All the other ungulates are going to be dealt with by P. J. White.  He’s got a big job, since bison get two talks today and everybody else just gets one.  PJ’s also with Yellowstone Center for Resources.

P. J. White: What I was asked to talk about today is just some of the trends in the ungulate populations through the park.  I’ll primarily be talking about the northern range in the west central part of the park, mostly because that’s where I spend all my time.  That data was collected in collaboration with a bunch of people, and so I don’t forget them I’d like to acknowledge them now...the US Forest Service Geological Survey, Montana Fish, Wildlife and Parks are all collaborators with us on these ungulate trend counts, and also Montana State University in the central part of the park. Time permitting then I’ll also talk about some of our findings from our winter wildlife monitoring with regard to motorized recreation, again primarily in the west central part of the park.  And that’s done in collaboration with Resource Management Dan Reinhart, Craig McClure and  ? (Pat Paratee) ?

We’ll start with the northern Yellowstone elk, which have been a subject of rather intense debate for about 80 years probably, and many varied management actions. As most of you are probably aware during the 1930’s up till 1968 the park actually actively removed elk by either shooting or trapping due to concerns about overgrazing.  And during that period the state also had fairly liberal harvest outside the park so during that period about 70,000 elk were removed from the northern range.  In 1969 the park kind of shifted management philosophies into what’s commonly called natural regulation.  They ceased the removals of elk from the park and went to allowing weather, density, predators and other factors to influence elk numbers. And you can see at the same time, starting over about here, the state also reduced the harvest to virtually nothing.  So we did see a period of rapid growth, from about 1969 to 1976, very rapid growth, in the elk population, from about a count of 4,000 up to above 12,000. Thereafter from 1976 to around the 1990s the population growth rate slowed though it still increased up to about a count of 19,000 some elk.
 
This slow, or slowing of the growth rate during this period has generally been attributed to the population approaching the capacity of the range, in other words the numbers increasing to a point where there was less forage per individual and that affecting reproduction and survival so that the growth wasn’t as quick.  The one thing that’s interesting and I think needs to be considered is if you look at the harvest down here by the state outside the park, you see in 1976 they ramped up the harvest again, due to concerns again about  increasing elk numbers and overgrazing of the winter range.   In about the early, or mid 1980s, they switched from primarily a bull harvest to primarily an adult female harvest, which has very different effects on the population because with females you’re obviously removing the reproductive driver of the population.  So this slowed growth rate could also be due to this increased harvest level.  And my point here is that even though the park went to a philosophy of not removing or culling animals from the herd, there was still intensive management through the harvest outside the park.

And then the next change in philosophy if you will, or management was in 1995 and 6 when the park restored wolves to the northern range.  Thereafter, as Doug talked about earlier we’ve seen a fairly substantial decrease in elk counts during the past ten years, where the count is about 50% of what it was in 1994.  Previously Doug kind of alluded to several factors we think that may have contributed to this decrease, including the drought which I’m not going to talk about much since he did. But the drought certainly can influence maternal condition, and through that birth weights and survival of calves.  

There are three important contributors I think to this decrease that we’ve seen.  And I should point out that most of this decrease, or the very rapid part of it has been since about 2000.

First, I’m going to say that wolves have been a significant factor in the decrease of this population. To be honest I have little patience for listening to people say they haven’t had an effect, especially when we brought them in here partially because we had an abundant elk population. So I think it’s somewhat silly to say that they haven’t had an effect.  But that’s just my opinion I guess (laughs). But, as an example, if you look at as numbers of wolves increased on the northern range, and there’s the wolf to elk ratio, we’ve seen a decrease in recruitment.  And certainly this is not a conclusive figure, but recruitment in the last four years has dropped to about 12 -14 calves per hundred cows, and been very consistent, and very consistently low I should say.  So I maintain that wolves are having an effect on the population.

Second, Kerry Gunther talked about it earlier. There has been an increase in the grizzly bear population in the greater Yellowstone area, which this figure shows. The increase within the park and on the northern range is probably been much less than this. But what we’ve found in the past few summers looking at calf mortality is that bears are accounting for about 50 to 60 % of the calf kills that we’ve monitored, that we’ve tagged the calves. And this is a much higher percentage than a similar study back in 1987 to 1990, which bears were responsible for about half as many of the proportion of deaths.  So it appears that bear predation, at least in the past couple summers, has been very high on young calves.

Thirdly, I think the hunt has been a significant contributor to the decline in elk in the past years.  This is a figure showing the elk count on the bottom and the percent of the total count harvested on the left there.  As I said, in 1994 our count was around 19,000, and as the population has decreased over time since then, the percent of the population that’s been harvested has increased, so the state has maintained the harvest, at least up to 2002 at similar levels prior to the introduction of wolves. The level of harvest essentially stayed the same, and what that means is an increase in proportion was harvested each year. And what this does is accelerate the rate of decrease in the population. And this continued from about 1995 – 2002.  Over here on the left you see the reduced permit quotas, and that’s the last couple years. The state has cut the permits for the late hunt, primarily, and this has gotten away from this accelerating trend of decreasing the population. In fact the state for next year has proposed to cut the number of permits to about 100 for the late hunt which would be a substantial cut from the 1100 this year. If that continues then I would expect the growth rate of the elk population, I should say the decreasing rate, to slow somewhat and hopefully get out of this rapid rate of decrease.
  
There’s a lot of debate on what will happen in the future, with various people predicting a population of elk on the northern range ranging from 14,000 animals all the way down to 4.000, with people predicting it to go down that low, and to be honest we don’t know.  The million dollar question, even if they cut the hunt, is when will the wolves respond to decreasing elk numbers, in other words when will the wolf numbers start to go down and predation off take go down.  As Doug talked about this morning there’s some indication that’s starting to happen, but it remains to be seen.

The next population that I’d like to talk about is the central Yellowstone elk which inhabits the Madison, Firehole, and Gibbon drainages.  It’s a non-migratory population, very different from the northern Yellowstone elk.  As you can see from about 1965-1998 when wolves colonized those drainages the population kind of bounced around, an equilibrium of about 550 elk. It’s a very severe winter climate there. The primary cause of death prior to wolf colonization was winter kill; animals would starve to death during severe winters. And then under favorable conditions the population would build back up again through better recruitment. As I said wolves colonized this area in about 1998, and by about 2001 there was a significant number of wolves using this area. I believe 30 - 40 wolves used it the past couple winters.  And we have seen again a pretty significant rate of decrease in the elk population, from over 600 counted down to 250 the last couple winters.  This decrease has been tied fairly closely to wolf predation.  The primary cause of death for collared elk there now is wolf predation.  Wolves have reduced recruitment even after we account for the effects of snow pack and severe winters. Recruitment is lower now than prior to wolves colonizing this area.

This is a very interesting system because it is heavily dominated by bison in the winter; it’s much different than the northern range which even now is an elk dominated system.  And wolves in this system have started to kill substantial numbers of bison, which is much different than the northern range.  In fact this winter about 30, 35% of the wolf kills have been bison, which I think on the northern range is probably less than 5% I would imagine.  So the interesting question here is if wolves can switch to bison, and make more of their diet bison they may be able to keep high wolf numbers in this system, which means that they can keep the pressure on the elk, because they’ll always select elk which are easier to kill. And we may be looking at a shift here of the elk population going down to 100 - 150 elk, due to fairly consistent wolf predation on them.

Now we’ll switch to pronghorn.  These are on the northern range, they winter in the Gardner Basin, and then about 2/3 of the pronghorn migrate up the elevation gradient to as far as the Lamar in the summer, with 1/3 of them remaining in the Gardner Basin throughout the year.  Pronghorn are a species of special concern for the park, primarily due to the low numbers and concerns that kind of a random event like disease or a severe winter could drive them down to very low numbers.

One of the things that’s interesting to me is prior to where this figure starts back in the 1940’s and 50’s the park also culled pronghorn, due to concerns about there being too many on the winter range.  Then it got to the 60’s and pronghorn were down to around 150 being counted, and all of a sudden, I think it was Doug  ? (Houston)? said “Wait a minute. We’re getting down there and we need to be thinking about how many we have”.   And so the culling was stopped and you can see that during this period for about 15 years the counts are relatively stable, around 150. And then all of a sudden we had this dramatic increase up to almost 600 over a period of 10 years or so. And then within 3 or 4 years the numbers crashed down to about 250 animals and they remained relatively consistent since then.   

I wish I could sit here and tell you a nice story about this increase and decrease, but to be honest I have no idea about why the hell it happened (laughter).  We have looked at all the data we can find, talked to other people, tried to tie it to increased irrigation outside the park, decreased coyote numbers, precipitation, many things, and we just don’t see a signal. Right now I can’t explain what happened.  It seems to be a critical event, so if you have any ideas I’d like to hear them certainly.   And we’re still working on it. But at least over the past ten years there seems to be new kind of equilibrium level of about 200 - 250 animals, and its remaining relatively constant.

Bighorn sheep counts, this is just for the northern range.  Most of you probably are aware that back in the early 1980’s there was a pinkeye epidemic in the sheep on the northern range, centered around the Mt. Everts wintering area, that decreased the population about 60 %. We haven’t seen a recovery from that epidemic. Sheep are notorious for slow growing populations, but they haven’t rebounded from that even though we’ve seen no sign of the disease since then. 

We started standardized surveys in 1995 with the Northern Yellowstone Cooperative Wildlife Working Group. These go from Point of Rocks out to Lamar, and the counts are shown here. And they are relatively, again relatively consistent, relatively stable. One thing I would like to point out is there hasn’t been a substantial decrease in bighorn due to wolves, which is commonly reported in the paper. We don’t see, we’ve seen very little wolf effect on bighorn, very little predation at all.

Mule deer counts, again this is the northern range, and recruitment is indicated by these columns. Again the counts have been variable within about 1500 to 2500, just bouncing around within that time frame.  Again, it’s often commented there’s been effects due to wolves from the reintroduction in ‘95, but we haven’t seen them or detected them. The interesting thing to me about this is if you look at the trend in recruitment in the columns in the bottom of the figures they pretty much pattern the trends in the counts, with a lag of a year or two. So this is suggesting that recruitment is essentially driving the population differences in these population estimates. And so probably adult survival is pretty high with recruitment varying and being responsible for the differences in the count.

Mountain goats are considered a non native species for the park.  They were reintroduced by the state of Montana in various areas in the Absorkas, I believe in the 1940s and 50s. They started to invade the park I guess back in the late 1970’s and have essentially increased exponentially our counts in and near the park, near meaning along the boundary of the park. This invasion if you will has primarily happened in the northeast and northwestern corners of the park. There is established recruitment in the park, especially in those two corners. We are seeing goats, a lot of goats, in the eastern part of the park but we haven’t seen consistent reproduction or recruitment there, so it seems to be somewhat slower there. This is considered a non native species, which has ramifications for the park.   Most of you probably remember the trials and tribulations they had in Olympic National Park with mountain goats. But this is a growing issue I guess.  We have seen some alpine effects to alpine vegetation, increased barrenness of the ground, vegetation trampling. We had a grant to start looking at those effects more closely starting next year, but it’s now been delayed until 2008.  So right now we’re doing very little with goats other than counting them, but hopefully that will change in the near future.
 
Doing all right? (5 minutes) 5...

Well, I’ll go quickly through this. There are two big issues regarding wildlife with motorized winter recreation. One is, has grooming of the roads affected the abundance or distribution of bison, which I’m not going to talk about at all today.  Rick will get into that after this.  The second is, how does this motorized recreation affect the behavior and energetic costs essentially of wildlife.   During 1999 – 2005 we sampled more than 8,000 interactions between bison and elk, and over snow vehicles and the associated people. To go very quickly, the responses of the wildlife that we’ve seen have been very minor to moderate. If you look at this, most animals either look and resume what they’re doing or show no response. Some maintain an agitated state but they stay in place. About 13 % move, I mean walk away from the people or the vehicles, and only 2% show a very active flight response, which means moving away, running, or my favorite, actually attacking or running at the people on the vehicles. (Laughter) So in general this is a relatively low energetic cost for all of these interactions.

Some of the things that increase the likelihood of them responding...certainly if they’re on or in the road they respond more. As you increase the number of vehicles in a group the animals are more likely to respond. Likewise if there’s less wildlife or smaller numbers in a group they respond more, and then if they’re in areas with less cover they tend to respond more. So all this is relatively intuitive, I think.

Interestingly, as use increases over the winter what we see is the active responses by bison and elk decrease, which suggests to me that they habituate to the motorized recreation. Again these animals have to be there, it’s their wintering area, it’s where their forage is. It’s a very severe winter environment, and they either need to deal with the use, or die, essentially, and it seems as though they’ve habituated somewhat to it.

I think a key point is we haven’t seen any evidence of a population level effect during the period of motorized winter use. What I mean by that is that there’s no indication that the populations of bison or elk have decreased, or that motorized winter use has affected their survival, essentially. To illustrate this, this solid line shows the winter use over time increasing from about 1,000 users in early 1960’s to over 140,000 in the early 1990’s.  You can see that the bison population, these black columns, increased very rapidly over the same time period of increasing winter use, and the elk population, the purple columns, remained relatively constant.  So I don’t see a smoking gun here at the population level, which is essentially how we manage wildlife. For that, I guess my opinion is that the issue of motorized recreation on wildlife, at least the energetic effects to wildlife is largely more of a social issue than a wildlife management issue. It really comes down to what people are willing to tolerate. And I might tolerate more behavioral effects to wildlife than someone else. These effects seem to be largely at the individual level, and they’re not seeing decreases in survival at the population level, or numbers at the population level.  And I guess I’ll just end it there. Any questions?

Audience Member: On this mortality of elk calves, how do you tell the difference if one of Doug’s wolves goes up and kills a calf, and then one of Kerry’s grizzlies (Laughter) chased the wolves off?   How do you tell who did what?

P. J. White: Well, in that situation we probably couldn’t.  These calves are pretty small. When the wolves get them they’re generally hauling large pieces back to the dens, it’s during the denning season.   So there’s not much there, they deal with it very quickly. Thank you.

Audience Member: What was the question? I didn’t hear the question, Paul’s question.

P. J. White: How do we tell the difference if wolves kill a calf, how can we tell if bears come in after it and take it over. I mean we do have cases where we don’t know if a wolf or a bear killed it.  We categorize it that way.

Audience Member: Did you say that mountain goats were reintroduced to the Absorkas, and if they were reintroduced how come they weren’t in the park way back when when they were in the Absorkas.

P. J. White: They weren’t reintroduced, they were introduced. Thank you. (Applause)