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Ecological Studies of Wolves on Isle Royale

Annual Report 2005-2006*by

Rolf O. Petersonand

John A.VucetichSchool of Forest Resources and Environmental Science

Michigan Technological UniversityHoughton, Michigan USA 49931-1295

31 March 2006

*During the past year, major support for these studies was received from the National Park Service (Co-op Agreement No.CA-6310-9-8001), National Science Foundation (DEB-0424562), Earthwatch, Inc., and the Robert Bateman Endowment at theMichigan Tech Fund.

Additional contributions were received from the following organizations and individuals: Dorthey L. Behrend, Sheri A.Buller, Greg and Janet Capito, Alison J. Clarke, Donald C. Close, Ronald and Barbara Eckoff, Edith N. Greene, MaryHindelang and Mark Silver, Horace and Mary Jackson, H. Robert Krear, Stephen and Deborah Laske, Meghan Oldfield andChris Lowry, Michael and Kari Palmer, Janet L. Parker, Tony and Thelma Peterle, Rolf and Carolyn Peterson, J. and LindaSchakenbach, Mary D. Seffens, Joan Silaco, Billie E. Smith, Milt and Althea Stenlund,William and Cynthia Veresh, John W.Weisel, and Dorothy D. Zeller. At Michigan Tech,William A. Tembreull, Arlene Collins, Diane Keranen, and Angela Johnston(all of the Office of University Communications) were instrumental in producing this report.

The following Earthwatch volunteers are gratefully acknowledged for their important contributions including personal timeand financial assistance:

Team 1A: Patrick Aird, Kazuko Baba, Erik Freeman, Rick Glatz, Lynda Thompson, and leader Greg Wright.

Team 1B: Marcy Erickson (staff-training), David Gates, Lawrence Kettner, Matthew Kettner, James LaRochelle, andleader Tim Pacey.

Team 2: Clay Ecklund, Ron Eckoff, Barry Goldstein, Daniel Lee, Joanne Patman, and leader Jeff Holden.

Team 3: Dan Mahoney, Kim Thomas, Mike Thomas, and leader Greg Wright.

Team 4A: Lee Cooprider, Brigitte Grov, Matthew McFalls, Benedict Mejchar, and leader Rolf Peterson.

Team 4B: Alex Englund, Eric Englund, Carman Kessler, Leslie Linser, Adam Scribner, and leader Jeff Plakke.

Team 4C: Sonia DaSilva, Allison Plute, Johann Schlager, Rick Weiss, and leader Sam Gardner.

Tax-deductible donations to support continuing research on Isle Royale wolves and moose are greatly appreciated and canbe sent to Wolf-Moose Study, Michigan Tech Fund, Michigan Technological University, 1400 Townsend Drive, Houghton,Michigan 49931-1295.THANK YOU to all who help!

Photo credits: Inside of front cover and inside of back cover by George Desort, Rolf Peterson, and John Vucetich; backcoverand fig. 17 by George Desort; frontispiece, figs. 4b, 4c, 5, 11, 22, and sidebar on pg. 16 by Rolf Peterson; and cover, figs. 3, 4a,6, 7, 9, 20, and sidebars on pgs. 11-12 and 14-15 by John Vucetich.

Results reported here are preliminary and, in some cases, represent findings of collaborators; please do not cite any materialcontained herein without consulting the authors.

5/06

2

Ecological Studiesof

Wolves on Isle Royale

“The more we come in contact with animals and observe their behaviour, the more we lovethem, for we see how great is their care of their young. It is then difficult for us to be cruel inthought, even to a wolf.”

I. Kant’s Metaphysics of Ethics

Personnel and Acknowledgements In summer 2005, Rolf Peterson and John Vucetich

directed ground-based field work, aided by MattAbbotts, Reid Andress, Marcy Erickson, Sam Gardner,Carolyn Peterson, and Leah Vucetich. Fieldworkcontinued from early May through August. In 2006, theannual winter study extended from January 19 toFebruary 28. Peterson, John Vucetich, and pilot Don E.Glaser participated in the entire study, assisted in thefield by Leah Vucetich and the following personnel fromIsle Royale National Park: Jean Battle, Kate Goodwin,Phyllis Green, Beth Kolb, Marshall Plumer, and MarkRomanski. Bert Frost, Deputy Associate Director of theNational Park Service, visited the study in January. SteveMartin from Isle Royale helped with mainland driving,and Bob Glaser and Jack Huhta provided invaluablelogistical help on the mainland. US Forest Service pilotsWayne Erickson, Dean Lee, and Pat Lowe flew several

supply flights to Isle Royale from Minnesota. Dean Beyer,from the Michigan Department of Natural Resources,provided important technical assistance, and SteveSchmitt (Michigan Department of Natural Resources),Scott Fitzgerald (Michigan State University), and MarkJohnson (Wildlife Veterinary Resources) all assisted ininterpreting a wolf necropsy. Several photographerscontributed in a variety of ways: George Desortparticipated in the winter study, shooting still photos andvideo; Jim Brandenburg provided a high-definition videocamera for aerial use; and John and Ann Mahan reportedfinding the skeleton of a radio-collared wolf washed ontoshore, posting their photos athttp://www.sweetwatervisions.com/Pages/IRwolf.html.During the course of the year, many park staff andvisitors contributed key observations and reports ofdead moose (and two additional dead wolves).

Figure 1. Wolf and moose fluctuations, Isle Royale National Park, 1959-2006. Moose population estimates during 1959-1993 werebased on population reconstruction from recoveries of dead moose,whereas estimates from 1994-2006 were based on aerial surveys.

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Summary During 2005-2006, the wolf population was unchanged

in number, thirty in all, while moose declined for thefourth year in a row to 450 (fig. 1). The ratio of moose towolves, 15-to-1, is the lowest ever documented at IsleRoyale. Three territorial wolf packs raised a total ofseven pups, offsetting a mortality rate of 23 percent inthe past year.Wolves maintained a high rate of predationon moose, and one pack invaded the territory of theneighboring pack and appropriated at least two kills.

Moose calves, relatively abundant in summer 2005, butsubject to intense predation pressure, were relativelysparse in winter 2005. The wolf population hasmaintained itself on cohorts of moose born in the early1990s. The effect of moose ticks diminished somewhat inspring 2005, but hair loss was still common in winter2006. Moose will probably decline further, until wolfnumbers decline. Inter-pack conflict in 2006 wassignificant, resulting in the death of one alpha male.

The Wolf PopulationDuring the 2006 winter study, the wolf population

contained thirty individuals, a number identical to theprevious year. This is the third year in a row of relativelyhigh wolf numbers, partitioned into three territorialpacks that have maintained their integrity since 2000(fig. 2, p. 4).Wolf social organization and maximum packsizes changed little from last year:

East Pack III (EP) . . . . . . . . . . . . . . . . . . . . . . .9Middle Pack II (MP) . . . . . . . . . . . . . . . . . . .13 Chippewa Harbor Pack (CHP) . . . . . . . . . . . .82006 Total . . . . . . . . . . . . . . . . . . . . . . . .30

We observed dispersing wolves and “loners”infrequently in 2006, so our wolf estimate is based on the

maximum number of wolves observed in the threeterritorial packs between 26-30 January. Usually theMiddle Pack numbered eleven while Chippewa Harborand East packs commonly numbered six to eight wolveseach.

Two wolves had long-term radio-collars thatcontinued to transmit: male 670 (alpha male in EastPack, collared in 2001) and female 410 (alpha female inChippewa Harbor Pack, collared in 2003). Alpha female1071 from the Middle Pack, collared in 2001, is still aliveand recognized by her radio-collar, but the radio signalfailed in 2003. Two-year-old female 1060 died just priorto the 2005 winter study, and her carcass was recoveredfrom a beach in May 2005 (fig. 3, p. 4). Two additional

Wolves

Moose-Wolf Populations1959–2006

Moose

4

wolves from the East Pack were collared withouthandling in summer 2005, and one of these transmittersproved very useful until it fell off during the 2006 winterstudy (see sidebar, p. 16).

In 2006, four of the six breeding individuals (fig. 4, p.5) in the wolf population were identified by radio-collaror appearance as the same breeders in 2005. Two veryold alpha wolves (female in East Pack and male inChippewa Harbor Pack) died in the past year and werereplaced by wolves of unknown origin that wereprobably much younger. The East Pack female died inlate September 2005 on a park trail, and her intactcarcass was recovered and necropsied. She weighed 45pounds and apparently had starved to death, probablybecause of an “incarcerated bowel,” the pathologists’term for a partially strangulated hernia. The ChippewaHarbor male was killed when the East Pack invaded on31 January and caught him and a pack-mate on a moose-kill (fig. 5, p. 5 and sidebar, p. 11).

During 21-26 February, courtshipbehavior was observed in all threepacks, but copulation was not observed.The alpha pair in the Middle Pack islong-established, but in the East Pack, apresumably young female was paired offwith a very old male (fig. 6, p. 6). TheChippewa Harbor Pack lost its alphamale on 31 January, but by 21 February amale was showing preliminary courtshipbehavior toward the alpha female oflong-standing, also quite old. If shesurvives until spring, we anticipate thatthree litters of wolf pups will again beborn, one in each pack. Anothercourting pair was evident in the EastPack, but they engaged in relatively littlecourtship behavior while underobservation by the alpha pair (fig. 7, p. 6).

Annual mortality (23 percent) during 2005-2006 wasnear average (fig. 8, p. 6). Three of the seven wolves that

died in the previous year were recovered—carcasses oftwo washed ashore while the third (identified by DNA asthe alpha female from the East Pack) was found deadfrom starvation on a park trail (see above).

The key event during 2006 was the conflict thatensued when East Pack repeatedly moved into landstraditionally held by the Chippewa Harbor Pack. Moosedensity in the East Pack territory was markedlyreduced, especially the formerly moose-rich Blake Pointpeninsula on the northeast end of the island. After theEast Pack killed the Chippewa Harbor Pack alpha male,the Chippewa Harbor Pack retreated to the middle oropposite side of its territory and seemed to be verymuch on the defensive. East Pack scent-markedprominently, traveled extensively within formerChippewa Harbor Pack territory, and seemed to have asolid claim to some of the highest concentrations ofmoose on the island.

Ironically, the kill rate of the Chippewa Harbor Pack

Figure 3. Radio-collared female 1060 died on or under theice of Lake Superior in January 2005, and her carcass wasrecovered from the beach of Siskiwit Bay in May. Cause ofdeath was unknown.

Figure 2. Wolf pack movements and moose carcasses (all fresh wolf-kills) during the winter study in 2006. All three of the packswere observed scent-marking.

2006 Wolf Population Organization and Kills

was higher than either of the other packs, but itscontinued existence is uncertain because of territorialencroachment by the East Pack. Compared to the long-term average kill rate of about two moose per wolf per100 days, the kill rate of the CHP (2.6) was aboveaverage while the EP (1.4) and MP (1.2) attained below-average kill rates. Kills were invariably well-used, soscavengers found few leftovers (fig.9, p. 6).

The present island-wide ratio of fifteen moose perwolf is the lowest recorded in the past 48 years on Isle

Figure 5. Pilot Don Glaser inspects the scavenged carcass of the alpha male from the Chippewa Harbor Pack, killed on 31January (left) when the invading East Pack surprised him on a moose carcass (see sidebar, pp. 11-12). This uncollared wolf hadvery heavy toothwear (right).

Figure 4. At least four of the six pack leaders in 2006 werehighly experienced and probably 8-10 years old. Top leftphoto: Alpha female (radio-collared, front) and the whitishalpha male of Middle Pack. Right top photo: Radio-collaredalpha female of the Chippewa Harbor Pack. Right photo:Radio-collared alpha male of the East Pack.

5

6

Royale (fig. 10, p. 7), but it seems unlikely that it will persistlong at this level. With one exception, all the moose-killscollected in 2005 were either calves or more than thirteenyears old.These old moose were born during years of rapidexpansion when the moose population experiencedrelatively little predation. However, these abundant cohortsof moose are soon to expire completely, leaving a moosepopulation with a relatively young age structure. For thisreason, we expect wolves to decline in the next year or so,allowing the moose population to stabilize. It is now evidentthat there were no changes in the leadership of all three

Figure 9. Wolves relied primarily on old adult moose duringwinter 2006.

Figure 8. Wolf population size (top) is explained bypatterns of mortality (middle) and reproduction (bottom).

Figure 7. (Left) Beta male 1423 (after radio-collar was lost) in mutualcourtship with a subordinate female in the East Pack. (Right) The East Packalpha pair carefully scrutinized the second courting couple, and onlysometimes intervened.

Figure 6. The East Pack leaders in 2006 includeda newly-recruited female (left) and a very old(and tired?) male, radio-collared in 2001.

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Wolf Population/Mortality/PupProduction1971–2006

packs for at least the past five years, but two alphawolves have died in the past six months. It is possiblethat stable leadership by experienced wolvescontributed to pack success in recent years (fig. 11).

During the 2005 visitor season,“fearless” wolves wereseen near human concentrations in Windigo (May) andRock Harbor (July). The wolf near Rock Harbor becameknown as male 1423 after radio-collaring (see sidebar, p.16), and he is a relatively high-ranking (beta) male in theEast Pack. Analysis of fecal DNA (an effort headed by Dr.Leah Vucetich at Michigan Tech) will allow us todetermine his age and trace his history. In 2004, a two-year-old radio-collared wolf (female 1060) entered theempty tent of a lone camper at Hatchet LakeCampground, but this wolf died in early 2005. Fearlesswolves are a public safety concern, heightened by thepossible death from wolf attack of a young man inSaskatchewan in November 2005 (see www.wolf.org).Virtually all recent wolf attacks on humans in NorthAmerica have involved wolves habituated throughaccess to garbage or foods provided by humans. At IsleRoyale, visitors are routinely instructed in “leave notrace” principles, including proper food storage and

garbage disposal. Park staff are continuing to focus oneliminating all access by wolves to other human-derivedfood sources (e.g., disposal of fish offal).

Figure 11. The Middle Pack roams over three-quarters of Isle Royale. Moose are sparsely distributed in this area, and the packdid not face challenges from neighboring packs in 2006.

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Figure 10. The number of moose per wolf has declinedsteadily over the past three years, to one of the lowest levelsobserved at Isle Royale.

Moose/Wolf Ratio2003–2006

During February 2006, the moose population wasestimated at about 450 animals (+/- 90 percentconfidence interval of 330-590), or 0.8 moose/km2 (fig.12), about half the level of three years ago. The ninety-five moose counted on ninety-one census plotscomprised 11 percent calves (fig. 13), slightly belowaverage. It is likely that high mortality from intensepredation pressure led to the 16 percent drop in moosenumbers from 2005 to 2006. During the summer 2005field season, calves were relatively numerous, at forty-six calves per one hundred cows. No twin calves,however, were observed by project personnel duringeither summer or winter in the past year.

Unusually warm temperatures, that characterizedspringtime weather in several recent years, moderatedsomewhat in 2004,probably leading to thedecline in moose ticksobserved on moose inspring 2005 (fig. 14, p. 9).We continue to map hair-loss patterns for mooseobserved in spring, andthese surveys provide ourbest long-term data ontick abundance.

Carcasses of twenty-four dead moose werediscovered during aerialsurveys in the 2006 winterstudy, and fifteen wereinspected on the ground(fig. 15, p. 9). All of thesemoose were killed bywolves, and one kill wasobserved (see sidebar, p.14). About one-third of thekills were calves, near the

long-term average for wolf-kills in winter. Twelve offourteen moose killed by wolves exhibited significantloss of fat from marrow cavities, suggesting relativelypoor condition (fig. 16, p. 9). Hot weather wasnoteworthy in July 2005, possibly contributing to poorforage intake during the growing season.

Snow depth was relatively low prior to the 2006winter study, and snow remained stable and uncrustedduring the study. Neither moose nor wolves seemeddramatically affected by snow conditions. Moose movedto coniferous cover by the end of January, and wolvesmade extensive use of shoreline ice for travel.Collaborating filmmaker George Desort observed onemoose at the west end for several days in earlyFebruary, and he recorded foraging primarily on

The Moose Population

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Figure 13. Moose calf abundance (at approximately six months of age) on Isle Royale, as aproportion of the total population. These are best estimates, a weighted mean of aerial countsin fall and/or winter.

Calf Cohorts as Percent of Total Moose Population1959–2005

2006 Moose Distribution

2.50 moose/km2

0.52 moose/km2

Figure 12. Moose distribution on Isle Royale was more uniform than usual in winter 2006. Only two strata were delineated, basedon habitat types and results of the aerial counts on ninety-one plots that comprised 17 percent of the main island area.

9

balsam fir, northern white cedar, and lichens, withsignificant eating of snow on all days (fig. 17, p. 10). Wespeculate that snow provides required water duringperiods when forage intake is extremely low (winterforage may contain 50 percent water).

There have been significant shifts in moosedistribution in the past two years. After many years ofuniformly scarce moose on the western two-thirds of IsleRoyale, the Houghton Point peninsula on the island’ssouth side at the west end has emerged as a majorconcentration area. At the other end of the island, thezone of high moose density has shrunk, leaving theBlake Point peninsula at the extreme eastern end almostdevoid of moose. The East Pack made no kills there in2006, after more than three decades during which thisarea was a reliable provider of moose. It is not known ifthese shifts in moose densityresulted from movement ormortality. We do know thatthe East Pack has huntedintensively in the Blake Pointarea during both latesummer and winter for manyyears, and the prey supplythere may have simply beenexhausted.

Ph.D. student Joseph Bumpis investigating the nutrientflows from wolf-killed prey atIsle Royale and YellowstoneNational Parks. He has foundthat soil nitrogen and sodiumcontinue to increase for atleast two years beneath thepoint where wolves breakinto the rumen, or four-chambered stomach, while consuming theirprey. Wolves don’t eat the plant matter in amoose’s stomach contents, but they generallyspill the highly liquid stomach contents on theground while feeding on internal organs. At IsleRoyale, Joseph has found that animal-derivednitrogen increases even two years after a kill inlarge-leaved aster plants growing at the kill site.Because the presence of wolves affects wheretheir prey live and die, wolves may influence thespatial heterogeneity of nutrients for plants andsubsequent feeding by animals that seeknutrient-rich vegetation.

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Figure 14. The extent of moose hair loss in spring, caused bywinter ticks, declined in 2005 after four years of increase.Circles represent individual moose, heavy bars are annualaverages, and smaller bars mark the interquartile range.

Figure 16. Long-term trends in moose bone-marrowfat. Data for calves (which best reflect currentconditions) represent mean levels, whereas data foradults is the proportion with greater than 70 percentmarrow fat.

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Figure 15. Moose mortality rate in midwinter was above average in 2006. All of the recordedmoose mortalities resulted from wolf predation.

Average Moose Deaths/Day1974–2006

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Forest VegetationThe forests of Isle Royale provide the context and

foundation for long-term fluctuations in wolves andmoose. The widespread stands of regenerating balsamfir at the east end of Isle Royale provided the foragebase for most of the island’s moose population duringthe past decade, following the catastrophic moose die-off of 1996. Moose survival was apparently higher at theeast end in 1996, providing the population base forquick recovery. A third wolf pack developed after 1999,and during 1999-2006, two wolf packsshared the eastern one-third of theisland with about half of the moosepopulation. Moose on the westerntwo-thirds of the island continued tobe sparsely distributed and theMiddle Pack hunted over acorrespondingly larger area.

Semi-annual counts of tagged,mature balsam fir trees at the westend indicate a steady and lineardecline in the number of live treeswhich continued unabated into 2006(fig. 18). Consequently, the mortalityrate of the remaining trees is steadilyincreasing, as expected for oldindividuals. Only about 20 percent ofthe 473 trees tagged in 1988 are stillalive. Along this transect there areonly six regenerating balsam firstems, all inaccessible to moosebecause of their location on highrocks or crevices along the rugged

shoreline. All mature fir trees at the west end appear tohave rotten cores. They probably were established acentury or more ago when no moose were present, andmany die after cracking off near the base duringwindstorms typical of the late autumn season. On 9November 2005, one of these storms contributed toabove-average mortality in mature fir. We project thatall tagged trees will have died by 2009-2010.

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Figure 18. Balsam fir trees in the forest canopy that were tagged in 1988 havesteadily died off without replacement. The remainder of our sampled trees areexpected to die by approximately 2010, an indicator of a dramatic reduction over75 percent of Isle Royale in seed source for this species.The demise of this speciesis ultimately caused by moose herbivory.

Figure 17. One bull moose observed for several days on Beaver Island in February 2006 ate snow frequently (left) as well asarboreal lichens (right).

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Isle Royale, 1/31/06, 4:55pm The airwas still. The lightly overcast skyforetold the coming of a fresh blanketof snow.

Chippewa Harbor Pack (CHP) hadkilled a calf in late afternoon theprevious day. Now they rested. Threewolves occupied the east end ofChickenbone LakeÑone sprawled outon the ice while two pups play-wrestled with great enthusiasm. Thealpha male and a subordinate wolfchewed bones and hide at the calfcarcass in the forest a half-mile to thenorth. The alpha female and two othersubordinate wolves were beddedbetween the kill site and ChickenboneLake.

This was the third moose CHP hadkilled in eight days, and the wolvesÕbellies were full. But the pack hadengaged in risky behavior recently,killing moose on the fringes of itsterritory. Just a few days earlier, thesewolves had made a kill in countryoccasionally patrolled by MiddlePack, their neighbors to the southwest.Now, CHP was pushing its luck on theborder of East Pack territory.

And EP was on the move. They hadnot made a kill in eight days. This wasan especially difficult winter for thispack with nine hungry mouths to feedand the lowest number of moose in itsterritory in decades. For four days thepack had rested at their last kill site,just north of Daisy Farm. On 30January, they left the Daisy Farm areaand spent the entire day wanderingand resting.

EP traveled north to the MinongRidge on 31 January. By 9:30 AM theyhad made Robinson Bay. Aftersleeping away most of the midday,they continued southwest toward theirmutual border with CHP. By 5:10 PM,the EP had reached McCargo Cove.Eight wolves of EP were present,traveling deliberately, mostly in singlefile.With no apparent hesitation, EP cutsouth and uphill into the forest at acreek that drained into the south sideof McCargo Cove.

They crested a hill and crossed anopen swampÑsingle file all the way.Their travel had all the appearances ofhunting; it was purposeful Ñmovingthrough more difficult and hilly terraincovered by deep snow and dense

vegetation. Were they hunting moose?Or did they somehow detect that CHPwas only 600 meters away? CHPappeared to be unaware that EP wasso close.

As EP crossed the swamp, their pacequickened. Pushing further south theypassed through another thick strip offorest separating two open swamps.After punching through the forest andon to the second swamp, EP was lessthan 400 meters from the two CHPwolves (including the alpha male) atthe carcass.

How and when did EP know that

CHP was just ahead? EP probablysmelled CHP; the wind was to theiradvantage, though very light. Andthere were ravensÑabout twenty atthe carcass, more than usual. EPcertainly heard them.

After crossing the second swamp,there was no doubt EP intended toseize their neighborsÕ kill, now justahead. And as for the CHP wolve s Ñthey seemed to have no clue aboutwhat was happening.

On the south side of the swamp, EPrallied, wagging tails and howling.Still, CHP did not respond.

Wolf Wars, 2006 John A.Vucetich

Aerial photo of the landscape surrounding the area where East Pack killed thealpha male of Chippewa Harbor Pack.

Map of the local area where East Pack killed a wolf from Chippewa Harbor Pack(CHP). The line shows the travel route of East Pack. Sites A and B refer to sitesdepicted on page 12. C is the site where CHP had killed a calf. D is the site whereEast pack killed the alpha male of CHP.

(continued)

Other WildlifeThe National Park Service conducts

aerial surveys of known osprey and baldeagle nests each summer. After regionaldeclines in organochlorine pollutants in theLake Superior watershed, both species re-established at Isle Royale in the 1980s.Eagles and ospreys are both present in lownumbers, and factors limiting furtherexpansion are poorly understood. In 2005,

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Figure 19. Relative snowshoe hare densityreaches a peak around the beginning of each newdecade, both at Isle Royale and on the mainland inMinnesota. Counts were made at Isle Royale during all hikes in May-August, while hares were counted in Minnesota on routes usedto count drumming ruffed grouse in spring (Minnesota Department of Natural Resources, with thanks to William E. Berg).

Then, EP ran to the southeast, swung around on thebackside of the kill site, and attacked, ambushing thetwo CHP wolves at the moose carcass.The chase lastedseconds and covered no more than thirty meters. Undera thick clump of trees, the lead EP wolf tackled the alphamale of CHP. Immediately, all of EP surrounded andmauled the CHP victim. In less than three minutes, EPleft only a lifeless carcass and blood in the snow.

Meanwhile, a half-mile away, two CHP pups onChickenbone Lake continued play-wrestling while thethird slept. After roughly ten minutes, a CHP wolf ran outof the forest and onto Chickenbone Lake, tackled thesleeping wolf and aggressively wrestled with it foralmost a minute. How does a wolf communicate toanother that tragedy has just taken place? It took severalmore minutes for the remaining three wolves of CHP toemerge onto Chickenbone Lake, and when they allarrived, they showed no sign of retreating to a saferlocation. Did the alpha female know what had happenedto her mate?

After spending another fifteen minutes on the eastend of Chickenbone Lake, the CHP wolves finally got upand ran, seven-abreast, westward, down ChickenboneLake, for about half a mile. They stoppedÑsome laydown, others looked back. Were they waiting for thealpha male?

During this entire time, EP was running, full ofexcitement, between the site of the dead CHP wolf andcalf-kill. The pack spent the next twenty-four hours atthis site. CHP, still missing their alpha male, moved thatnight to a much safer portion of their territory just northof Lake Richie, where they spent the next two days,mostly resting.

It is not unusual for a wolf to be killed by another wolf.In a typical year on Isle Royale, one to three wolves arekilled, and a typical alpha wolf may kill two to fourwolves in his or her lifetime. But, contrary to commonmyth, wolves do not kill others of their kind withoutreason. It is a matter of survival.Wolves kill other wolvesso they can have more food for themselves and theiroffspring.

Top photo: East Pack approaches the Chippewa Harbor Packkill site by traveling uphill through deep snow (Site A). Middlephoto: Moments after howling, East Pack, led by the alpha male,charges into the Chippewa Harbor Pack kill site (Site B). Bottomphoto: East pack surrounds and kills the alpha male ofChippewa Harbor Pack (Site D).

Wolf Wars (continued from page 11)

Snowshoe Hare Population Density1974–2005

active eagle nests numbered nine,with eight eaglets fledged. The num-ber of osprey nests was six (as in 2003and 2004), with seven young fledged.

Snowshoe hare observations werestill relatively low in summer 2005,consistent with a cyclical declinefollowing a peak at the turn of thedecade (fig. 19, p. 12). Red fox, amajor hare predator, have apparentlydeclined to exceptionally low levels(figs. 20 and 21), probably a result oflow food supply. Beaver havedeclined as forests mature and thehigh wolf population at the east endexerts predation pressure—only threebeavers were seen by projectpersonnel during 2005 field work.(The National Park Service plans tocount active lodges in October 2006;the last successful survey was in2002.)

River otters continue to thrive in allparts of the island. One unusuallylarge family group of six otters wasobserved at Washington Harbor inFebruary 2006 (fig. 22). The recentlyestablished American marten will bethe subject of a study by park staffbeginning in 2006. Although nomarten were reportedly observed inthe past year, fresh tracks of severalindividuals were recorded in winter2006 at the west end of Isle Royale.

Figure 22. River otters increased dramatically on Isle Royale in the early 1990s as several strong cohorts of lake herring becameavailable in Lake Superior. Herring abundance did not stay high, but otters persisted throughout the island and their scats arecommon on park trails near wetlands and shorelines.

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Foxes/100 hrsFoxes on Kills

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Observations of Red Foxes from Aircraft1972-2006

Figure 21. Relative abundance of redfoxes from aircraft observations in winter,1972-2006. Grey bar is the number offoxes seen away from moosecarcasses/100 hours, while the black baris the number of foxes seen on carcasses.

Figure 20. Facing a food shortage caused by low numbers of snowshoe hare (at amid-point in population trough) and fewer scavenging opportunities left by thehungry wolf population, red foxes have become relatively scarce. However, foxesare often raised in close association with public campgrounds, so they arefrequently seen in summer by visitors.

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John A.Vucetich

2/12/06, Isle Royale. Don Glaser, our pilot, had justpicked me up from Lake LeSage where I had spent thepast several hours snowshoeing into a site whereChippewa Harbor Pack had killed a moose a few daysbefore. I performed a necropsy and collected a fewbones that we’d later study in more detail.

Before flying back to Washington Harbor, our winterbase, we would make one final check on each of thepacks.

We found East Pack just as they were crossing to thewest side of McCargo Cove. Two weeks earlier, East Packkilled the alpha male of Chippewa Harbor Pack. Now, asthey crossed to the west side of McCargo Cove, theywould be in CHP territory.

I had been fortunate enough to witness East Pack killthe alpha male of Chippewa Harbor Pack. It was the mostdramatic wolf event I had ever observed. I expected itwould be some time before I’d see anything like thatagain.

We didn’t have much daylight left, so we couldn’twatch East Pack for long. After noting the direction oftravel and number of wolves, I suggested to Don that westart looking for Chippewa Harbor Pack. As we wereleaving the area, I noticed a bull moose feeding in athinly forested area just ahead and upwind of thedirection East Pack was traveling. Hmmm. Should we waitand see what happens? If we waited, we wouldn’t find theother packs. Besides, I’d seen this many times: a pack ofwolves tests or chases a moose, the moose escapes, andthe wolves regroup.

Don suggested that we wait to see what might happen.The moose was just about 200 yards ahead of East Pack.

It took a few minutes for East Pack to arrive at the otherside of the cedars where the land was more sparselycovered in aspen. Just as East Pack worked through a verythick stand of cedars, the wolves and moose saw eachother. They were perhaps 50 meters apart.

In an instant the bull turned and fled. The wolveswere quickly at his heels, and the moose stopped, spun

around and made a stand. The wolves skidded to a stopand then lurched back a few steps. The next moment,the bull was surrounded. Wolves grabbed any holdavailable at the moose’s rear. The moose tried to turnand face each lunge. But every turn left some areaexposed. For a brief moment, there was a break in thecircle of wolves. The moose bolted for that opening,heading for the thick cedar stand from which the wolvesfirst came. As the moose passed one of the wolves, itlunged and bit deeply into the moose’s right hindquarter.Running through deep snow, the moose dragged 80pounds of wolf, attached by sharp, powerful canine teeth.With each forward lunge, the moose struck the wolf in thebelly with its rear leg.

After 20 meters, the moose broke free, but the wolvespursued. The moose didn’t quite make the edge of thethick cedar stand when the wolves caught up, and onemanaged to bite and hang onto the moose’s hindquarter.The moose slowed down considerably. A second wolfleaped up and latched onto the moose’s rear.

Now the moose was moving slowly enough for thealpha male to run to its front end. Although the moosewas stopped, it was still standing and extremelydangerous. The alpha male waited and maneuvered tofind a safe angle and timing for his attack. But the moosenever yielded such an opportunity, and the alpha malenever succeeded.

During this time, four wolves, about 320 pounds, hadgrabbed the bull’s rear end, causing his hind legs tocollapse. Amazingly, the moose’s front remained upright,and still no wolf could bite his nose and, unbelievably, themoose shook himself free from all four wolves and stoodup. He was, however, surrounded by the nine wolves ofEast Pack. Some were focused and waiting for the rightmoment to attack; others milled around just waiting tofeed.

After several minutes, one wolf attacked, then asecond, third, and fourth. The moose’s rear was broughtto the ground once again where it remained for severalminutes. The pounded-out snow had begun to turn pinkand then red with the moose’s blood. After a few minutes,

The Rare Observation of a Common Occurrence:East Pack Kills a Moose

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the moose managed to once again shake the wolves.This cycle of being brought half-down and thenrecovering repeated itself two more times. In the finalcycle, forty minutes after the wolves first chased thebull, his front end collapsed. As the once powerful andmagnificent body of this bull moose hit the ground, allnine wolves struck the moose and began tearing itsflesh from all sides. From the ground, he could nolonger kick. For a few moments, the wolves fed whilethe moose was not quite dead.

At some unknown moment, the moose’s life endedand the life of the East Pack wolves was renewed. Thismiracle of passage occurs several times a week onIsle Royale. Worldwide, more than 250 species live bythe flesh of other warm-blooded animals. Except forplants and scavengers, all animals require the flesh ofsome other organism. In such a world, if one is aware,no day is routine. Only lack of awareness makes theday seem routine.

Photo series: East Pack in successful pursuit of a bull moose inthe usual range of the neighboring Chippewa Harbor Pack.The chase lasted a few hundred meters before the wolvespulled the moose down by hanging onto its rear. A wolfsecured a nose-hold only after the moose was down andimmobilized.

Figure 23. Snow depth (daily),ambient temperature (hourly), andwind speed (measured hourly atRock of Ages lighthouse) during the2006 winter study on Isle Royale.

Wind Speed Barametric Pressure

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Weather, Snow, andIce Conditions

Snow depth was average andstable during the 2006 winterstudy (fig. 23). On the other hand,temperatures were considerablyabove-average early in the study,then declined to near-averagelevels by the end of February. Atno time was there an ice bridgeto the Ontario mainland, and formost of the winter study, verylittle ice existed, even inprotected bays of Lake Superior.During the 2006 winter study, asin 2005, winds (reported everyhour at Rock of Ages lighthouse)were somewhat stronger thanaverage. Excellent f lyingconditions require wind speedsof less than 25 km/h. In a typicalyear, calm conditions prevailabout 40 percent of the time.This year, however, winds wereless than 25 km/h for 33 percentof the time (fig. 23). Also, windsexceeded 50 km/h for 12 percentof the time (typically, windsexceed this value for about 8percent of the time).

Snow Depth, Temperature, and Wind Speed on Isle Royale, Winter 2006

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For the past two years, we have beenattempting, along with researchers in three otherlocations, to devise a way to radio-collar a wolfwithout capture or handling. Such an advancewould not only facilitate research in wildernessareas and national parks, but also expandopportunities for attaching radio-collars in winter,when foot-hold traps cannot be used because ofthe risk that wolvesÕ feet might freeze, and indensely forested areas, where helicopter-dartingis impossible. The idea is not new Ñ over fortyyears ago, Lou Verme from the MichiganDepartment of Natural Resources published anarticle on self-attaching collars for deer.

In summer 2005, we were finally ready to deploythese collars for wolves at Isle Royale, using adesign that followed, for the most part, onedeveloped by Ron Schultz from the WisconsinDepartment of Natural Resources. The device usesa snare that incorporates a radio-transmitter andantenna into a fabric Òdog-col lar,Ó with abreakaway link that detaches the collar after it ispulled tight over the neck. Ideally, after the wolftugs briefly at the restraint, the breakaway givesway and the newly-collared wolf simply runs off.Foxes can shake off the collar over their smallheads.

We weakened the breakaway from the Schultzdesign, making it easier to release, but this allowedwolves to release themselves before the collarattached. After retrofitting a stronger release in mid-summer, two wolves were radio-collared in a month.One collar ended up on a mature male from the EastPack, and it worked fine until the fateful day in lateJanuary when his pack attacked and killed the alphamale from the Chippewa Harbor Pa c k Ñ we foundthe collar lying on the ground at the site of thebattle. The second successful collaring ended whenanother wolf simply chewed through the heavynylon fabric.

The device has proven to be safe for wolves andfoxes, but the presence of non-target animals is amajor consideration. In 2005, we deployed theself-attaching collars through the summer periodand, unfortunately, one young moose calf wascollared in early June (when it was evidently notfollowing its mother). MurphyÕs Law is not to beignored. With timely assistance from Dean Beyerof the Michigan Department of Natural Resources,we were able to immobilize the mother with atranquilizer dart, but were unsuccessful incapturing the calf, by then weighing about 75 kg.Mitigation planning continued on our part but,within a month, wolves intervened and killed thecalf. In future work we will avoid deploying thedevices when moose calves are young, but thebasic approach has promise and we will continueto attempt improvements.

Can Wolves Radio-Collar Themselves? Rolf O. Peterson

Top and middle photos show adult male from East Pack (1423)before (July 2005) and after (February 2006, wolf on right) beingradio-collared with a self-attaching device. Bottom photo shows thecollar after it was pulled off in a violent skirmish with theneighboring pack.