Fauna Series No. 5

Fauna of the National Parks — No. 5 The Wolves of Mount McKinley

CHAPTER TWO:
WOLF (continued)

Food Habits of Wolves (continued)

DISCUSSION OF FOOD ITEMS IN WOLF DIET

Caribou.—The main food supply of the wolves in Mount McKinley National Park, as well as over interior Alaska in general, is the caribou (Rangifer arcticus stonei). Both young and old animals are taken. During the calving period greater attention is given to calves. Remains of adult caribou, including calves in their first winter, were present in 267 scats; calf remains were found in 313 scats. The remains include hoofs, foot bones, and pieces of the long bones.

In the Mount McKinley National Park region there is a local caribou herd numbering at least 20,000 and possibly as high as 30,000. This herd as a unit has existed since the early 1900's and probably for a great many years before that. Its movements, which vary greatly over a period of time, are not known in detail but the animals inhabit an area which at one time or another includes Broad Pass, all of the park, and the Lake Minchumina district. At times they probably extend their range east of Broad Pass. Most of the animals move through the park over a period of a few weeks in May and June, at which time the resident wolves live mainly on the calves which they run down. The movements of the caribou and their hunting by wolves is discussed in detail in the chapter on caribou, beginning on p. 144. After the main bands have passed on, a few stragglers are always left behind. Often little groups and lone animals are up in the headwaters of the streams near the glaciers in the crest of the range. Although these stragglers are scarce the wolves seem to find them and continue to subsist mainly on caribou during the summer months after the large bands have moved westward.

In winter at least a part of the caribou herds generally are to be found along the north boundary, both within and outside the park. Those wolves living in the park then move down to the caribou to secure their food but still make occasional trips into the sheep hills. The park wolves in winter are not entirely dependent on the caribou, for sheep are also available to them. But when caribou are present among the sheep hills they probably furnish the bulk of the food supply.

Not all the animals eaten by wolves are killed by them, for caribou are frequently found that have died of other causes. However, it appears that most of the caribou eaten by wolves are killed by them. It is not known what proportion of the adults killed are weak, but it seems probable that the weaker animals are the first to be taken.

No doubt the caribou has been the main source of food for centuries and are adapted to hold their own in the presence of a wolf population under natural conditions. Wolf numbers might vary and perhaps cause the caribou numbers to fluctuate some but the relationship is old and tried.

Dall Sheep.—Remains of adult sheep (Ovis dalli dalli) were found in 304 scats, and those of lambs in 42.

Adult sheep were not preyed upon extensively during the summer. At three dens only four scats contained adult sheep and only one contained lamb. Probably more sheep remains were not found at the dens because in 1940 and 1941, when the dens were observed, calf caribou were readily available and formed the bulk of the food. If a den had been observed in 1939 no doubt more sheep remains would have been present, because in that year calf caribou were not available in the eastern half of the park until early June.

In 1940 and 1941, after the bulk of the caribou had left the vicinity of the den and only stragglers were available, the food of the wolves was supplemented by rodents rather than sheep. This would indicate that at this time the wolves were more disposed to capture rodents than to run down sheep, even though many sheep roamed the hills only a few miles from the dens. Further discussion of the predation of wolves upon sheep is given in the chapter on sheep beginning on page 62.

Ground Squirrel.—Ground squirrels (Citellus parryii ablusus) were found in 174 scats. At the rendezvous used by the East Fork wolf family during July 1941, ground squirrels occurred in more than one-third of the scats. About one-fourth of the scats gathered at the rendezvous in 1940 contained ground squirrels. During these two periods, caribou were scarce which probably accounts for the heavy utilization of these rodents. Along with ground squirrels, marmots and mice were also utilized more than usual at this time.

Ground squirrels are abundant from low to high elevations. They are an important food supply to foxes, eagles, and gyrfalcons (Falco rusticolus), as well as, at times, to wolves.

Marmot.—A total of 114 scats contained remains of marmot (Marmota caligata caligata). Like ground squirrels, the marmots hibernate all winter and thus are available for food for only about 5 months. They are abundant, living usually among cliffs or loose rocks and boulders. Marmots weigh up to 17 or 18 pounds and therefore furnish considerable food even for the wolf. They can be methodically hunted by wolves with success, so in lieu of other game would furnish subsistence to a certain number of wolves. They are quite vulnerable to attack. I have frequently come upon marmots which I could have captured easily if I possessed the speed of a wolf or dog. They often range some distance from their holes. Once I saw a group of six large marmots move from one cliff to another about 200 yards away. In one place marmots often traveled 500 yards across an unprotected route. O. J. Murie reports that his Norwegian elk hound, which resembles a small Husky dog, captured a large marmot with little trouble, and I saw him run down another which he bit at but did not hold. This last one was almost captured, even though, along with some others, it had been scolding the dog that was approaching in plain sight. Their vulnerability is also indicated by the fact that coyotes have been known to subsist almost entirely on them in bighorn range in Wyoming. The largest number of marmot remains were found at the wolf rendezvous at a time when caribou were scarce. The wolves at this time were resorting to marmots far an important part of their food supply. The predation on marmots tends to check their numbers and so moderate their consumption of vegetation among the cliffs used by sheep in winter. The extent of the control is not known. Probably the wolf's predation by itself would be ineffective, but combined with the activity of other predators it may play an important role in controlling marmot numbers.

Mouse.—Mouse remains were found in 73 scats. The mice available were the lemming (Lemmus yukonensis), red-backed mouse (Clethrionomys), and four kinds of meadow mice (Microtus) In analyzing the mouse contents no effort was made to segregate the species. Several scats were made up entirely of mouse remains, as many as six occurring in one, but often only traces of a single mouse were found.

When caribou are plentiful the wolves do very little mousing for they prefer to feed on the larger game animals. But even when feeding mainly on big game the wolves will sometimes turn aside to pounce on a mouse. In the fall considerable mousing by the pups and one or two adults was observed.

On May 3, 1940, an adult wolf on East Fork River was seen hunting a mouse in the snow. He pounced with legs stiff, much in the manner of a coyote, in order to break through the crust. After the pounce he dug in the snow but I could not be sure that the mouse was captured.

On September 10, 1940, at Polychrome Pass, an adult wolf was observed hunting mice for an hour on a flat grown up in dwarf birch and sedge. During this hour it made about 17 pounces. It then traveled briskly toward the Toklat River, turning aside occasionally to catch a mouse which it heard or smelled along the way. Usually in pouncing on a mouse it did not hop up in the air and drop on it, but pounced in a more nearly direct horizontal line, much as a dog would do. On one occasion it went up in the air more than usual and so vigorously that on landing it went off balance and its hind quarters swung to one side. Often it made a short run of five or six jumps before pouncing. Twice while it hunted it stopped to howl. When looking for a mouse—one for which it had pounced and not captured—it wagged its tail, the rate of tail wagging increasing with the rise of its excitement, which in turn was dependent upon the nearness of the mouse.

On the morning of September 17, 1940, I watched the East Fork family from a vantage point near Polychrome Pass. A black pup hunted mice by itself a half mile from the others for almost 2 hours. A yellowish pup hunting mice in some tall grass, played with one it had captured, tossing it in the air a few times and catching it. Apparently the pup was not hungry. The presence of magpies (Pica p. hudsonia) and an eagle, and the uncovering of a cached morsel by the gray female, were evidence that the wolves had finished a feed on larger game earlier in the morning. At 1:15 p. m., after a rest of 3 hours, the yellow pup went off hunting by itself. The usual method of pouncing was noted, but sometimes there was hardly any jump and only the forepaws would strike forward to press the mouse to the ground.

On the morning of September 23, 1940, three pups about a quarter of a mile apart were moving eastward over the broad flats at Polychrome Pass, probably to join the rest of the family. They were constantly attracted by mice to one side or the other, and they followed up grassy swales where the hunting was good. In about an hour one of them lay down in the open and the other two disappeared behind a slight rise in the tundra.

On September 24, 1940, the East Fork family was still at Polychrome Pass. While the others were resting, two pups hunted diligently for mice a half mile away. These two pups hunted from 8 a. m. until noon. In the afternoon one of the pups was again seen hunting mice. At this time, when the main caribou herds were elsewhere and only stragglers were available, the mice seemed to form an important supplement to the food supply, especially for the pups, but also for the adults. A number of sheep were only 2 or 3 miles from the rendezvous where the wolves were hunting but still were apparently not much molested.

Perhaps the wolf would feed more on the mice if it did not take so many of them to make a meal. Mice are large enough to serve as a staple diet for a 10-pound fox or a coyote, but are probably a little small for a 100-pound wolf to depend on, especially if the mice are not plentiful. I do not know how many mice would make a full meal for a wolf. As an average-sized field mouse weighs only a few ounces, many of them would be needed to furnish a meal of 7 or 8 pounds. One evening in September I tossed in quick succession to the tame wolf pup, which had a surplus of dried salmon and scraps available and was not especially hungry, 19 mice and 2 shrews. These were caught in the air and swallowed so rapidly that each one hardly stopped in the mouth. There was no evidence of satiety after the last mouse was swallowed. But when mice are plentiful a wolf would probably be able to subsist very well on them.

In winter I found little evidence of feeding on mice, but no doubt they are often eaten at this season, and in winters when the mice are exceptionally abundant, as in 1938—39, they probably feed considerably on them. Exceptionally deep snow would, of course, make mousing difficult.

Moose.—Remains of moose (Alces gigas) were found in nine scats. At Savage River some pieces of thick moose hide had been chewed. The evidence gathered indicates that moose are not readily taken by wolves. Probably at times under certain conditions moose may be preyed upon, especially if they are in a weakened state due to scarcity of food or disease. The majority of trappers interviewed were of the opinion that ordinarily wolves were not a menace to moose.

Porcupine.—Remains of porcupine (Erethizon epixanthum myops) were found in eight scats. In the woods at Toklat River where porcupines had killed many spruces I found the nearly complete hides of three porcupines turned inside out. Two wolf droppings found nearby contained only porcupine remains, including large stout spines. Other skins neatly turned were also found. It is well known that it is not uncommon for coyotes to kill and eat porcupines, and there are considerable data to show that the fox also feeds on them. A wolf shot May 10, 1940, contained porcupine quills under the skin of the muzzle and front legs.

Former Chief Ranger Louis Corbley had a Husky dog which a few years ago killed many porcupines. The technique used by the dog was to keep circling the animal and worrying it until an opportunity came to seize it by the nose. The dog kept his hold, then as the porcupine relaxed, a deeper hold on the head was taken, which usually was fatal. The dog deftly turned the porcupine over on its back, while still grasping its head, and if still alive, quickly killed it. The killing was so skillfully done that the quills were usually avoided. A wolf would be able to use a similar technique.

Back in 1927 there were unusual numbers of porcupines in the park. One could see dozens of them with out any trouble, according to all reports. The animals are still fairly common. In places entire groves of trees have been killed by girdling. At timber line, where the growth is scattered, there are places where every tree is killed, thus serving as a pressure to push timberline down the valley. However, I have noticed many seedlings coming up in some of these areas so that these advance patches of timber are recovering.

Snowshoe Hare.—The snowshoe hare (Lepus americanus macfarlani) was represented in only three scats, a scarcity correlated with the extreme scarcity of hares. Only in a few spots along the north boundary was any appreciable hare sign noted.

According to the monthly wildlife reports for Mount McKinley National Park, the big die-off took place in the summer of 1927. Since that time the hares have remained rare over most of the park. In a memorandum accompanying the November 1942 wildlife report for the park, Chief Ranger Grant H. Pearson states that when the hares were dying during the last epidemic, small blisters appeared all over their bodies under the skin, and that dead hares were to be seen everywhere. Some were even observed as they fell over and died. (The blisters were possibly caused by the larvae of the tapeworm Multiceps serialis.)

Although hares in Mount McKinley National Park have been scarce since about 1927, in other parts of Alaska they have become numerous since then and in some of these areas they have again disappeared. For instance, in 1939, from the railroad, I saw many dead hares near Fairbanks.

If hares were plentiful they would probably supplement the food supply of wolves considerably. In 1923, when I observed them in Mount McKinley National Park, I am sure they were plentiful enough to furnish subsistence for a number of wolves.

E. A. Preble (1908, p. 212) reports that one band of wolves near Fort Simpson lived largely on hares, many of which were taken from the snares of the natives. J. F. Stanwell-Fletcher (1942, p. 138-139) reports wolves in British Columbia hunting snowshoe hares in late February when there was a firm crust on the snow. Earlier in the winter the hares had been able to escape the wolves in the soft snow. No doubt the abundance of the snowshoe hare is an important factor in wolf ecology.

Beaver——The beaver (Castor canadensis canadensis) is widely distributed over the park but is not abundant.

Remains of beaver were found in two droppings. In 1941 a dead female, found by Wildlife Ranger Clemons, represented potential carrion.

Red Fox.—The red fox (Vulpes kenaiensis) is numerous in the park, but remains were found in only one scat. One trapper told me that wolves frequently ate foxes they found in his traps. All evidence points to the fact that in Mount McKinley National Park foxes are little molested by wolves.

Wolf.—Wolf remains were found in one scat. In the spring of 1939, remains of a black wolf were found which had been eaten by other wolves. A trapper told me that he knew of several wolf carcasses which had been eaten by wolves.

Ptarmigan.—Remains of ptarmigan (Lagopus spp.) were found in six scats. Ptarmigan are probably taken incidentally and possibly some represent carrion as they not infrequently fly into the telephone wires. There are three species of ptarmigan available but the willow ptarmigan (Lagopus lagopus alascensis) is the only one which becomes sufficiently abundant at times to be of some importance as a food. At the present time the willow ptarmigan is far from its peak of abundance but recovering somewhat from the low part of the cycle.

Grass and sedge.—Remains of coarse blades of either sedge or grass were found in 21 scats. Grass is eaten at all seasons. Some of the droppings containing grass also contained several round worms, so seemed to act as a scour. On June 27 I saw a black male eat grass for a few minutes. He left a watery scat in the road which indicated his stomach was not quite normal. Later he vomited up some of the grass he had eaten.

Garbage.—Garbage remains were definitely recognized in five scats. Wolves seem to visit garbage dumps readily. The garbage dump of a road camp near Polychrome Pass was visited regularly by wolves during the summer of 1940, and they have often been seen at the Savage River Camp seeking garbage. During the winter. wolves have at times stayed around Park Headquarters seeking refuse.

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Last Modified: Thurs, Dec 20 2001 10:00:00 pm PDT
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