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Northern Wyoming 


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Copyright © 2013 Travis N. Wood

Moose of the Greater Yellowstone Area
And Questions of Predation by Wolves

Historically, moose in Wyoming were rare to non-existent. According to their History of Moose Management in Wyoming and Recent Trends In Jackson Hole, Brimeyer and Thomas of the Wyoming Game and Fish Department (WGFD) wrote, "Few if any moose were believed to exist in the Yellowstone and Jackson Hole areas of Wyoming prior to 1850." Early explorers of that same area who kept detailed journals did not mention moose. And there is no archeological evidence of moose living there. But after 1850 moose are believed to have migrated from Montana. Yet not until 1912, a century ago, were there believed to be even 500 moose in that area and in the entire state of Wyoming.


Moose population estimates are not very reliable. Moose are difficult to count, but population estimates cannot be gained by a summer resident standing on the ground around low elevation towns such as Jackson or Dubois in the warmer months of the year when moose naturally seek higher and cooler areas. There are numerous factors that combine to conceal even the moose that are present. Moose do things to cool off during warmer months. They seek elevations much higher than the Dubois or Jackson area. They may retire to shaded forests during the day and come out during cooler nights. They leave riparian areas in which waterflow has been reduced — either from drought or from lack of snowmelt and rain in summer.

There simply is no valid rationale for claiming summer residence of an area qualifies a person to derive a population count. That is especially true when that summer resident admits to deep-seated prejudices and openly declares he does not care about a lack of evidence.

Predation on moose did not begin in 1995. Wolves did not appear in force with reintroduction. It required years for their numbers to expand from the few that were reintroduced. Meanwhile bears and mountain lions were well-established. And even after wolves reached population numbers capable of having an effect, research showed that bears were the primary predator on moose. Yet those bears were present during both expansion and reduction of moose populations. So if there is a coincidence, was predation also responsible for expanding the moose population?

There are numerous factors affecting moose decline. Among them are forest fires or forest fire suppression, loss of habitat to development, competition from elk that over-browse riparian areas, closing of artificial feed grounds, prolonged and severe drought (as evident in the last decade), severe winters such as 1988-89 and 2010-11, parasites such as worms and ticks, loss of shade from the devastating pine beetle epidemic, hunting especially of moose cows, traffic fatalities, and so on.

Wolf predation simply cannot explain the ups and downs of Western moose populations. In 2006, as shown below, moose populations were considered expanding both where wolves were present and where they were not. More recently, populations were thought to be declining — also both where wolves were present and where they were not.

Wyoming moose populations are still historically high. In 2001, six years after wolves as a species were returned to their native habitat in Wyoming, moose populations were estimated at 13,657, a 26-fold increase over a century ago. That's 2700% of 1912 populations. As with other populations that approach saturation levels and carrying capacity, it could well be that there was nowhere for the moose population numbers to go but down. And decline has been reported.

But compare Montana: That state also has wolves and the Montana Pioneer reported that in 2008 Montana had a stable population of only about 4,800 moose. Yet that number was considered evidence of a "thriving" population in that state. In the same year, the smaller state of Wyoming reported a population of 7,700 moose — 60% more than Wyoming's larger northern neighbor, from which moose migrated to Wyoming to begin with. (See Annual Report for 2009, page A-5.)

So how is a current population of 7, 000 to 8,000 moose in Wyoming a tragedy when a population of only two-thirds that many moose in larger Montana is a great success story? We cannot reasonably expect populations to remain at or above historic highs in a state where moose were historically absent before mid-nineteenth century.

Now compare Idaho: In 2006, a decade after reintroduction of native wolves, and in the state with the largest wolf population in the Northern Rockies, the moose population was reported as "exploding" at a whopping 20,000 moose, a persistent increase of moose since wolves were returned to their native habitat there. The news report said, "Moose populations exploding across the West" — in areas both with or without wolves. In Idaho also moose were historically scarce or absent. So were wolves in 2006 responsible for the exploding population of moose in Idaho?

Wyoming and Yellowstone area moose populations — forest fires and feeding stations. The National Park Service says that, not wolf "control" (that is, annihilation and extirpation) of the early 20th century, but rather the "suppression of forest fires probably was the most important factor" responsible for the increase in moose numbers in the Yellowstone area up to 1988. But then a decline followed with the fires of 1988 and with the severe winter of 1988-89. Note that this decline does not coincide with wolf reintroduction, which was delayed to another seven years afterward.

But moose expansion in the Greater Yellowstone Area was also the result of several artificial moose feeding areas (see Brimeyer above, page 135):

  • "By the early 1980s there were 5 moose feeding areas approved by the Wyoming Game and Fish Commission along with several other unofficial moose feedgrounds.... Most of these sites were phased out by the early 1990s."

So if we are going to claim a coincidental decline of moose after 1995, why blame it on wolves instead of the closing of feeding stations?

Finding Wyoming Moose Population Estimates. The Wyoming Game and Fish Department (WGFD) recently restructured it entire website into entirely new web addresses that often make previous year's documents unavailable. Population estimates for moose in Wyoming continue to be contained in "Job Completion Reports" (JCRs) for each year. Those are further divided into "Big Game," "Migratory Game Bird," and so on. Moose figures are located under "Big Game," of course. But years previous to 2008 are no longer available, thus making previous population estimates even more difficult to locate.


"Job Completion Reports" are published by region. And there are seven game management regions in Wyoming. Each region is further divided into moose hunting areas and the "herd" that resides in that area. Population estimates for the Dubois hunt area and Dubois herd are found in the Lander Region, which also contains the Lander hunt area, of comparable size and habitat. The Dubois area is northwest of the Wind River Indian Reservation and bounded by the Continental Divide and Fremont County line. The Lander herd and hunt area is south of the Reservation. Both hunting areas contain habitat that ranges from desert to the alpine slopes of the Wind River Mountains. Each hunting area includes the river drainages emerging from those mountains. And each hunting area has a moose population goal of 400 animals.

Links to Job Completion Reports for the Lander Region by year are as follows:

  • 2008, Dubois Herd: pages 379-390; Lander Herd: pages 363-377.
    2009, Dubois Herd: pages 373-384; Lander Herd: pages 353-372.
    2010, Dubois Herd: pages 393-402; Lander Herd: pages 377-392.

Wolves among the moose, first appearance. Critics of wolf reintroduction claim that moose populations began a decline when wolves were reintroduced. The year was 1995, and those critics claim that it cannot be simply coincidence that moose population decline in that vary same year. They believe the wolves had to have caused the moose population decline.

There is indeed evidence that moose numbers began a decline in the Lander and Dubois herds in that same year 1995. The big problem with the critics' claim is that even though wolves were reintroduced in 1995, they did not arrive in the Dubois and Lander areas until years later. So the moose decline actually began before wolves arrived in the area. Evidence for the Lander Hunting Area is most striking. Game and Fish documents clearly show a steady moose decline for several years after 1995. But wolves were not resident in that area until 2007 — twelve years after reintroduction of wolves to Yellowstone Park, hundreds of miles to the north.

In the Dubois Hunting Area, there seems to have also been a moose decline beginning in 1995, but wolves did not arrive there until 1997 to 1998. And wolf numbers were small to begin with. But the Dubois area is tougher to document because Game and Fish has never been able to obtain good counts of moose in that area — before or after 1995. Yet we can consider the population counts of each area. To repeat, the population goals are 400 moose in each area.

The Lander Hunting Area moose counts. Annual Moose Populations for the Lander area since 1995 are given below:

  • 1995=439, 1996=417, 1997=391, 1998=383, 1999=379,
    2000=348, 2001=316, 2002=300, 2003=281, 2004=296,
    2005=314, 2006=339, 2007=315, 2008=321, 2009=326,
    2010=335, 2011=322

USFW annual reports show that a wolf pack did not form in the Southern Wind River Range, and wolf-pack territory did not include the Lander Hunting Area, until 2007. The decline in moose began immediately in 1995, twelve years before wolves reached the area, and the decline continued to year 2003. Then the moose population increased for three years in a row to 2006. Since 2006, the moose population in the Lander Hunting Area has been stable, varying slightly above and below about 325 moose. That's a small area with two-thirds the moose population of the entire state only a century ago. And those moose population figures are 75% of all-time historic highs of 1995 in that area.

The Dubois Hunting Area moose counts. The Dubois area, including the Upper Wind River DuNoir Valleys is the area that some folks claim has seen a dramatic decline in moose since 1995 when reintroduction of wolves began in the Northern Rockies. The DuNoir Valley in particular can be seen at this Acme Mapper link. Though the reintroduction of wolves began in 1995, they were planted in Yellowstone Park, far north of the DuNoir. It was not until 1997 when the Washakie Pack formed (see "Wolf Report, 10/28/1997") that wolves arrived at the DuNoir. And the Washakie Pack that year consisted of only a female with five pups. The alpha male was was blamed for killing cattle and shot by Wildlife Services soon after his arrival to the Dubois-Dunoir area.

(For origins and early history of the Washakie Pack, see Wolf Reports 2/12/1996, 10/28/1997, 10/30/97, 11/16/1997, 11/24/1997, 12/10/1997. For other Wolf Reports, see 1997 Wolf Update Reports, Reports from 1995 to 2003, or Reports from 1995 to 2006.)

The Job Completion Reports (JCRs) linked earlier describe the long difficulty of obtaining moose sampling counts and population estimates for the Dubois Herd. The most details are contained in JCR 2009, pages 373-384.

JCR 2010 merely summarizes in brief the same conclusions on the long history of lack of data that is found in the documents above. To summarize those and previous year's reports: There has never been a reliable count of moose in the area. Sampling sizes have always been too small and varied widely from year to year. Hence, there has been no population model developed for calculating the full number of moose. And hunter harvest data (hunter-killed moose numbers) are too small to mean anything.

But clearly the moose count sampling sizes only represent a small portion of the Dubois Herd. That becomes apparent when yearly sampling ("classification") varies widely from year to year. For example, when a count of 20 full-grown, adult bulls in one year is supplanted by a count of 40 full-grown, adult bulls in the next year, something is amiss. Obviously, the adult bulls were not born the previous year and therefore either were hidden from view during the count or moved into the area after the count.

Either way, the evidence suggests that a large majority of the herd has never been counted (or is moving in and out of the hunting area to which the count is restricted.) Yet for five years most recently, the small sampling size has averaged 84 animals, representing a herd most likely in the hundreds. Those numbers themselves do not evidence a devastating, wolf-caused decline in moose numbers for a herd with population goal of 400 moose. Remember, the Lander Herd with the same population goal of 400 dropped to as low as 281 before wolves ever arrived in that area.

Yet Game and Fish suspects the Dubois Herd has declined. And the probable causes are habitat deterioration due to drought and disease among the moose. (See discussion of these factors below. And see Appendix B of JCR 2009 (pages 443-447) for other details on problems of weather, drought and vegetation.) Nowhere does Wyoming Game and Fish blame wolves for the decline of moose numbers, and if any state would like to blame wolves, Wyoming would.

Testing dead moose. Because Wyoming hunters, outfitters and other critics of wolves can not cite real numbers for moose in the Dubois area, they resort to a case of nine dead moose in the year 2000 — and they leave out the details that clearly exonerate wolves. Each of the Job Completion Reports contains the following information.

In the year 2000, nine "non-hunting mortalities" are recorded for moose in the Dubois herd. None of those deaths were attributed to wolves by investigators. Not even one of them. On the contrary, not one of those nine moose showed signs of injury commonly associated with wolf attack, and not even one of those animals was scavenged by wolves after death. Perhaps a wolf pack may kill an animal on rare occasion and not consume the carcass. But how could a wolf pack kill nine moose, leave no bite marks, hamstring injuries, or any evidence of even taking a single bite from the carcass of the animal they supposedly killed to feed from?

Incidentally, the WGFD document says explicitly that not even one of those nine dead moose was tested for disease. The only moose tested for disease that year were the seven healthy moose that hunters harvested. The official cause of death of the nine moose was listed as "unknown." It is fair to say that if you want to know what killed moose, you test the dead moose, not only the live moose that hunters are taking. Testing for disease was not done on the moose that needed to be tested. What is known is that wolves did not kill them.

If your neighbor dies unexpectedly, an autopsy will be performed on his body to determine cause of death. What is unheard of is for authorities to go out upon the streets, kill some other person and perform an autopsy on him instead to determine why your neighbor died. There is a lesson here to be learned when critics of wolves try to blame them for the nine moose of year 2000. Those wolves were physically examined. Wolves did not kill them. So again moose populations over the years, and in the year 2000, suggest disease was the cause of any decline.

Comparison to moose populations in the Bighorn Mountains. It has been claimed that the Dunoir Valley (pictured below) northwest of Dubois has been the specific scene of the dramatic decline of moose.


The complaint is that while this decline was happening in the DuNoir, moose in the Bighorn Mountains were thriving. But that is not an accurate comparison. The Dunoir Valley area reaches an elevation of from only 7200 to 8000 feet. But moose in the Bighorns are rarely seen below an elevation of 8000-8500 feet, higher and cooler than the Dunoir Valley.

Additionally, moose in the Bighorns resort to forested areas for cooling shade. But the DuNoir slopes are predominantly treeless and offer no such protection.

Dr. Scott Becker, writing in Habitat Selection (p. 168) found that female moose in Northwest Wyoming chose summer habitat based upon a need to limit heat stress. Those summer ranges averaged a thousand feet higher in elevation than the winter ranges the moose selected.

Moose cannot survive warmer climates. Moose biology 101. The elevation is important. It is a well-known fact of moose biology that heat stress is a big problem for moose. Moose begin to suffer heat stress at temperatures of 57°F. Moose compensate for rising temperatures by seeking water and shade, and by decreasing their activity during the day and increasing that activity during the cooler temperatures of night time. But what happens during a severe drought when water becomes scarce?

Heat stress has been shown to reduce reproductive success, that is, lower the number of calves born each year. And heat stress has also been associated with malnutrition and disease. The moose pant so hard to cool off that they do not eat as much, and they become more susceptible to the parasites that they continually harbor but are able to resist when cooler and healthier. This source in particular from the Minnesota Department of Natural Resources shows that moose that die from heat-stress related problems are often listed in Minnesota under the cause "unknown," just as the nine moose in the year 2000 were listed in the Dubois area.

Even in normal summers, the temperatures in the Dubois area are high enough to induce heat-stress in moose. The Western Regional Climate Center shows that normal, summertime temperature highs in the Dubois area are well above 57°F, the temperature above which moose are known to suffer heat stress if they cannot find enough water in which to cool off. At temperatures above 68°F, the moose begin to pant heavily. So what will happen in a well-documented drought in the Dubois area? Whatever their numbers, they are not likely to be seen by residents and casual observers during the daytime, and at lower elevations.

Reported decline of moose coincides with long drought. Drought maps. Moose need water to cool off. But drought maps of the United States show clearly the progression of extreme drought in the Dubois Area of northwest Wyoming. The drought began rather suddenly by year 2000, and by end of year 2001, northwest Wyoming was in the red zone, considered extreme drought. That drought lasted 8 to 10 years. On the margin between mountains and desert, the Dubois area is simply not favorable climate for moose during prolonged drought — a far more persistent, and far better documented force there than roaming wolves.

The DuNoir valley empties into the Wind River about nine miles upstream of Dubois, Wyoming. Appendix A of JCR 2009 (page 436) includes the graph (to the right) of drought severity in the Wind River area, where the DuNoir and Dubois are located. The graph shows that drought progressed rapidly with approach of the year 2000, the same year that the nine dead moose were found in the Dubois Hunting Area.DroughtSeverityIndex.gif

Research published in June of 2013 shows that elk, a relative of moose in the deer family, tend to suffer low pregnancy rates because of drought but not because of the presence of wolves. The drought causes diminished nutrition, which causes a low pregnancy rate and thus the possibility of a population declining in numbers. The article, "Low Pregnancy Rates in Elk Not Due to Wolves" reports a similar connection long known between drought and domestic cattle. And it appears to be true also for moose.

Disease, Ticks, and Worms are widespread in Yellowstone Area Moose. A side-effect of drought and heat-stress is that moose can become more susceptible to disease and parasites. Even though the drought may subside, the parasites and disease can remain. Last year, the Jackson Hole News and Guide quoted John Henningsen, a disease biologist with the WGFD to say that as many as 50 percent of moose in western Wyoming are inflicted with the carotid artery worm. Henningsen says that the worm is a contributing factor in the states moose population declines.

At least one moose south of Jackson that likely died from the worm "appeared to be in otherwise good body condition," with no signs of wolf predation or even scavenging — remarkably similar in condition to the nine dead moose of the Dubois herd that WGFD failed to test in 2000. The parasite is spread by horseflies that do best when climate is hot and dry. The drier the summer the better the horsefly population does, and Henningsen noted, "I believe Wyoming's been in a drought for the last decade," thus bolstering the horseflies and the worms — and putting even more pressure on a moose population prone to heat stress during drought.

Ticks are also considered a contributing factor in the moose decline. As reported by Steve Kilpatrick, WGFD habitat biologist, moose in western Wyoming are often seen with a heavy infestation of winter ticks. Those ticks he lists with the worms, with forest fires or their suppression, with lack of nutritional quality of available forage, and with drought and climate change. We can also add traffic mishaps along the area's highways. Cars also kill moose.

On the question of wolves affecting the moose population decline, Kilpatrick writes, "Although the potential effects of predation cannot be discounted as a contributing factor, calf and adult survival rates indicated that predation was relatively low."

Finally, if a population has reached unacceptably low levels, the wise course of action is to quit killing them, quit hunting them, let them recover. And especially quit killing the females. But hunting continues, and during the most notable decline since native wolves returned to the area, that hunting included the females upon which the future population depended. In the Dubois area, females were hunted through 2004. In the most recent hunting season, statewide, 183 cows were killed by hunters. In fact, over a third of the yearly hunting fatalities are females.

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