NATIONAL PARK SERVICE Fauna of the National Parks of the United States No. 4 Ecology of the Coyote in the Yellowstone

Figure 8— The cow which has fallen was weak after the winter season of food scarcity.
Note the closely grazed banks along the river.
Madison River, April 16, 1938.

ELK AS COYOTE FOOD

ELK CARRION is an important source of winter food for the coyote and also furnishes considerable summer food. There are about 11,000 elk (Cervus canadensis nelsoni) in the northern Yellowstone herd, more than 7,000 of which were counted within the boundaries of the park in the winter of 1937—38, the remainder having crossed into the Absaroka National Forest north of Gardiner. Those in the park wintered largely on the north side between Mammoth and the Buffalo Ranch. Some of the bulls winter on the higher slopes along the upper Lamar River and on Mount Washburn. Formerly quite a number wintered in Hayden Valley but in late years scarcely any have been found there. A few are found along the Madison River and in thermal spring areas, such as Old Faithful, where the warmth in the ground melts much of the snow.

Each year, mainly in winter, a certain number of animals perish, usually the calves and the older adults. The "winter kill" may be due to a variety of causes, such as old age, necrotic stomatitis and other diseases, heavy tick infestation, and malnutrition. The losses are generally light, but in winters during which snow conditions are unfavorable they may be large. In the winter of 1936—37, when conditions for elk were favorable, losses were light and the coyotes went hungry. During the winter of 1937—38, losses were relatively large and so an abundant food supply was available to predators. The heavy crusted snow conditions prevailing during the entire winter, along with the scarcity of browse, such as Douglas fir, willow, and poplar, made conditions especially unfavorable to the elk. As winter progressed, the elk became thinner and the mortality mounted, coming to a peak in April. Elk carrion was so abundant that there were always carcasses on the range, untouched or only slightly eaten by coyotes, even as early as January. The rangers found more than 500 carcasses and in the course of my field work I came upon 282, half of which were found on the poorer range along the Yellowstone River. The number of animals found each month was as follows:

¹ Many of these had died in April.

A few elk die during the summer, thus supplementing the staple summer diet of field mice and pocket gophers. A total of 1,153 of the droppings collected, mainly during the spring, summer, and fall months, contained elk remains. In 1937, coyotes were observed feeding on a bull elk on June 3; a cow so weak she fell down several times was seen on July 14; and a thin weak cow still in the winter coat was seen on July 12. Elk hair is frequently found in coyote droppings during the summer. Calves are eaten during the calving season, and this food item will be discussed in considerable detail in the succeeding sections.

There was no evidence that coyotes killed elk calves in winter, and I feel certain that such predation must be light and that only weak or disabled animals, away from the main bands, would be attacked. In the following incident coyotes are reported to have been hunting a calf elk. Unfortunately the condition of the calf is not given. Reports of coyotes molesting elk are very rare. Observations of elk indicate that the relationship between coyotes and elk is usually similar to that described by former Park Naturalist E. J. Sawyer in his comments on the incident reported by Ranger Cottrell. The incident and comment from Cottrell's note (Yellowstone Nature Notes, February 1928, p. 4) follow:

I saw a calf elk running down the ridge at high speed and stopped to observe the cause of the excitement The elk was followed by a lone coyote at a distance of about 50 feet which was gaining rapidly as the animal approached. The calf stopped to fight the coyote away, and at this time four more coyotes appeared and circled the calf; all four were going in the same direction; they gradually closed in as they circled the distressed animal and the fifth coyote held it at bay. They had closed in and were rushing and snapping at the calf when I decided there was no chance for it to escape and opened fire on its attackers. I killed two of the coyotes and the others escaped. One of the coyotes killed had been struck and bruised by the elk in its frantic efforts at self-defense. I have seen six other calf elk during four recent patrols that had to all appearances been attacked and killed in this manner.

Comments by the park naturalist:

The above described incident recalls to mind that I have seen two or three coyotes at once close to a yearling elk so weak from winter conditions that it could hardly stand, and of course quite incapable of escape or self-defense. Yet the coyotes were merely circling ahout it. Again, along the Lamar River, at a point opposite Specimen Ridge I once came upon a young elk too weak to rise. Fresh coyote tracks in the snow round about indicated that these animals had reconnoitered the elk, but there bad been no attack. Returning by the same route a day or two later, I found the elk still there and still alive and all conditions as before.

It is not implied that coyotes pressed with hunger will not kill elk, deer, or antelope on occasion and under certain conditions. What is implied is this: that, under normal conditions of available food in the form of winter-killed animals—carcasses put out as bait, mice, ground squirrels, and so on—the coyote will not ordinarily kill any of the larger animals. He then even prefers to wait until elk, which he might easily kill, die of starvation. Finally, such weakened elk as the coyotes may destroy in late winter would be those most likely to succumb to weather and food conditions (winter-killed) in a short time; so that the coyotes' work in such instances is often an act of mercy, and, economically considered, an act wholly beneficial to the herd.

The following observation quoted from a typewritten report on trumpeter swan studies submitted in 1939 by Assistant Park Naturalist Frank R Oberhansley shows a calf elk-coyote relationship similar to that found by Sawyer.

March 17: On the right bank of the Yellowstone River about 2 miles below the mouth of Blacktail Deer Creek, a mature coyote (Canis latrans) was surprised at close range, gnawing upon an old weather-beaten elk skull. About 100 yards farther down stream an elk calf was encountered lying near the trail in such a weak and emaciated condition that it was unable to regain its feet. Fresh tracks of the coyote in the snow plainly showed that he also had seen the calf earlier that morning and that he actually detoured away from it in arriving at the old skull farther up the trail.

During the course of this snowshoe trip down the Yellowstone from March 16 to 18 inclusive, three other elk calves were observed in a weakened condition similar to the one described above.

Figure 9— After a hard winter this cow was so weak that she could hardly rise and stand. Note the odd appearance of the lower jaw while "grinding" the molars, an action common to many ungulates when in great discomfort or anger.
Below Cottonwood Creek, March 4, 1938.

Elk calf mortality.— During the calving season the coyote feeds extensively on elk calves as is evident by the occurrence of remains in 290 droppings. In 1937 carcass remains of 14 elk calves were found. The calf mortality noted seemed to be concentrated during the actual calving period, for the remains found were those of animals which were very young. Eight of the carcasses were found on the winter range which the majority of the elk leave before and during the calving period.

It is extremely difficult to determine what proportion of the calves are found as carrion and how many are killed by coyotes. In domestic animals we know that there is a mortality among calves at birth and shortly after birth. In wild animals we know less about this type of mortality, but we do know that there is a definite mortality at birth. In the spring of 1936, I found a calf moose about 2 or 3 days old which had been seen acting sickly the day before. He was one of twins. The mother was still in the vicinity, so the calf had not been deserted. Under the section on antelope an example of antelope fawns dying at birth is given. Presnall (1938), in discussing effects of an overgrazed deer range, writes: "A weakened condition of the deer has already been indicated in the high death losses during the winter of 1936—37. Also in the summer of 1937 several deaths in parturition were noted."

In regard to calf elk mortality at birth, O. J. Murie in his publication on the coyotes of Jackson Hole, Wyo., gives several instances of calf mortality in which predators were not involved. He writes: "It was discovered that calves of both elk and moose had been dying shortly after birth, and in the spring of 1931 eight dead elk calves were found, but opportunity was afforded to examine only one of these before decomposition began. While no positive conclusions were reached as to the cause of death, it was determined that natural enemies were not responsible. . . . The fact that eight dead calves were counted in a limited area, and that it is difficult to find such carcasses in timbered country, would indicate that the percentage of loss from this unknown ailment was fairly high."

In the spring of 1938 I made some special search for uneaten dead calves. Obviously, however, such a search is almost futile, for the calving ground is very extensive and even though many calves should die at birth it would be only by chance that a person would find a carcass, especially before coyotes had found and eaten it. The first day I searched for dead calves was on May 24. I found one which had just been born, for parts of it were still moist. The mother was feeding nearby and it was from observing her actions that I was able to find her dead offspring in a clump of sagebrush. This animal appeared to be normal but was rather small, weighing only 20 pounds (considerably below the average weight which is 30 pounds or more), and with the following measurements: total length 3-1/2 inches, hind foot 1-7/8 inches, ear 14 inches.

On May 28 from the top of a butte in the Horseshoe I saw two ravens fly to a distant spot and alight on the ground. On going to the spot, I observed that they had been feeding on a dead calf elk. The only marks were small breaks in the skin on the back and on the abdomen where the ravens had been feeding. The hair was slipping so that it had probably been dead a week. It was either born prematurely or had developed abnormally. The body was but little thicker than the legs, the carcass probably weighing about 10 pounds. Measurements were as follows: Total length 33 inches, hind foot 1-1/2 inches.

A few days later in Hayden Valley, Assistant Park Naturalist Oberhansley was attracted to the carcass of another calf elk. About half the carcass remained and it had decayed considerably. If killed by coyotes one would expect that it would have been eaten before any decay had set in, so it seems that this is another record of a calf that had died at birth.

The hard winters may increase the death rate of calves, since it has been found in studies of domestic animals that deficiencies in nutrition cause abortions and weakened calves. Furthermore, contagious abortion has been found in the elk so that some calves may be lost as a result of this disease.

In Jackson Hole O. J. Murie found each winter a few aborted calves. I have frequently seen coyotes in late winter among the elk herds and think it probable that the coyotes are attracted by the chance of finding an aborted calf or a carcass of an old animal. O. J. Murie writes about contagious abortion as follows: "Field observations, however, supplemented these tests, and each winter a number of aborted fetuses were found—10 or more being found in one winter. Considering that such fetuses are not readily found and that ravens often do away with the remains in a short time, it seems safe to conclude that a considerable number of abortions occur. An employee at the elk refuge observed one, but when the fetus was sought later in the day, it had disappeared. . . . One cow examined had died of necrotic stomatitis. Only a few feet behind her lay the aborted fetus." In certain cases the elk calf remains found in droppings might represent fetuses found by coyotes in dead cows, for some of the cows dying in the spring carry fetuses. Also some cows may die during the trials of labor and leave a calf to die.

Besides the calves dying at birth a few are no doubt occasionally lost accidentally or possibly at times are deserted. On May 27, 1938, Assistant Park Naturalist Oberhansley and I found a calf elk in a badger hole a few feet from where I had seen the animal the previous day. One leg was straight out behind in the hole in such a position that it did not seem probable that the calf could extricate itself unassisted. When we stood it up, its hind quarters quivered and it walked as though quite weak. This calf might have become carrion for coyotes if we had not happened along to help it.

On May 28, 1937, a band of 95 elk were following the Lamar River looking for a place to ford. As the river was high, the elk were hesitant in crossing. A cow some distance to the rear was followed by a wobbly calf, which kept lying down after following 10 or 20 yards at a time. The cow wanted to move forward with the herd. She looked alternately toward the herd and the calf until a group of five cows passed her on a trot. Following them, she joined the main herd one-third of a mile from the calf. The cows finally crossed the swollen Lamar River and it was not known if the mother returned to her offspring. The herd instinct and the migration habit were pulling strongly, and in this case it seemed that the calf may have been deserted although desertion of young is probably a rare occurrence.

There is a natural calf mortality at birth, and although there are relatively few records, those existing seem to be sufficient to indicate that a number of dead elk calves are available on the range as carrion.

Figure 10— A weak calf elk. During the latter part of each winter a number of such calves usually die from disease or malnutrition.
Below Cottonwood Creek, March 20, 1938.

MATERNAL PROTECTION

TO GAIN some measure of the potential coyote predation on calves an attempt was made to learn what opportunities a coyote might have for preying on them. The watchfulness of the cows with young and their action when coyotes were near were observed.

The calving period extends from the middle of May to about the middle of June. In 1937 the first calf was found on May 15 and the last newborn on June 18. In 1938 the first young was not found until May 23. The majority of the calves are probably born during the last few days in May and the first week in June, during the period in which the elk are migrating from winter to summer range. Many of the calves are born on the winter range, but more of them do not arrive until the cows have reached the summer range. Cows drop out of the traveling bands and go off by themselves to give birth to their calves. Many of them go to the open sagebrush and in a few days, when a calf has become strong enough to travel, the mother moves off with it to join any band of elk that happens to be moving past. As early as June 1, I saw eight calves traveling easily with eight cows which were moving at a brisk trot. In the Horseshoe and at the Buffalo Ranch bands of 50 to 100 elk were often seen resting near the edge of the trees while one or more lone elk would be out in the sagebrush, each with a calf. As the calves are brought into a herd a few days after birth, they have the benefit of the general protection offered by the band.

On May 25, 1938, at 9:30 a. m., an elk calf was seen in the sagebrush 15 yards from some scattered Douglas firs on the fringe of the woods. While I was watching the calf, it stood up, apparently to stretch, and lay down on its other side. It was still in the same spot at 2 p. m. No cow was seen, but one may have been resting in a nearby grove of trees. Calves lying alone do not stay perfectly still but occasionally stand up for a minute or two. This movement of the calves increases their exposure to predators, but the duration of the movement is probably too brief to add appreciably to the insecurity. Even if a coyote should see a calf, the mother would generally be near enough to protect it.

Figure 11— A coyote was seen plucking the hair from the near portion of this elk carcass while a raven sat on an antler watching him.
Swan Lake Flat, April 12, 1938.

Some observations were made which indicate that mothers remain close to their calves for several hours after birth and later stay near them. On May 25, 1938, at 10 a. m. a cow and newly born calf were seen in a clump of aspen. Fresh blood on the ground showed that the calf had been born that morning. The calf seemed barely able to rise but did so several times during the hour that I watched, and three times appeared to be nursing. After walking 7 or 8 yards to the edge of the grove, it would wander back to lie beside its mother. At 2:30 p. m. the cow and calf were still in the aspen grove. When the cow scented me, she tried to entice the calf to leave with her, but the calf was so attached to the grove that, after moving a few yards beyond its edge, it would return. This would cause the cow to return to the grove, and as she trotted off again the calf would follow a short distance but then retreat. The procedure was repeated several times. Finally the calf moved some distance from the grove and, after further coaxing by the cow, followed her on wobbly legs. The calf lay down in a hiding posture when I approached and the cow ran into the woods a short distance, returning almost at once when the calf cried as I lifted it.

On May 26, 1938, another cow was seen lying beside her calf on an open slope of Specimen Ridge, a little below a band of 60 feeding elk. When I was 40 yards away, the cow ran off with the band but was lying with her calf again an hour later. With head up, the calf watched me approach and was unafraid when I stroked it.

On May 28, 1938, in the Horseshoe, a lone cow was lying down in the sagebrush. In about 15 minutes she looked over her back toward her calf which had stood up 25 yards away and was walking unsteadily toward her. She met the calf, which nursed for about 5 minutes. The cow then walked off 20 or 30 yards to feed and the calf followed a few yards and lay down.

In the Horseshoe on May 29, 1938, a cow after grazing, lay down about 25 yards from her calf. This calf was tame and docile and would not bear its own weight at once when I stood it up. Young but apparently strong, it started up the gentle slope toward the aspens about one-third of a mile away where its mother stood watching. It lay down after traveling about 100 yards but got up again when it saw me coming. Seeing her calf approach, the mother trotted toward it a couple of hundred yards and two other cows followed her. When the three cows met the calf they all smelled of it and then turned up the slope, the calf trotting close to its mother. One of the cows struck at the calf, but I doubt if she intended to touch it. Often when a calf is thought to be in danger, one or more cows have been seen to join the mother and act as solicitous for the safety of the calf as the mother. On May 26, 1937, I found a calf just born, and while examining it was approached by the mother and nine other cows all excited and worried. They advanced and retreated several times.

On May 29, 1938, a calf lay near the highway at Tower Falls. All day the cow remained in the vicinity, afraid to come to her calf because of the traffic on the road, but at dusk she returned to it.

On May 31, 1938, at the Buffalo Ranch several observations were made showing that the cows remain close to their young calves much of the time. A calf followed a cow 25 yards and then walked off to the side another 25 yards and lay down. The mother fed within 50 yards of this calf for the half hour that I watched her and frequently looked toward her offspring. Another cow was feeding near her calf which had stood up to wander around in a patch of sagebrush, later joining the mother to nurse, and then alternately walked and trotted after its mother as she moved off about 100 yards. Another cow was seen lying down beside its calf for an hour, and still another was lying 30 yards from its calf which was resting on a patch of short bright green grass. On June 2, there were a dozen single cows in the sagebrush in the Buffalo Ranch area, each looking after her calf.

Figure 12— So many elk died in 1938 that the coyotes were unable to clean up the carcasses and thus minimize water pollution, as in other years.

Most of the observations which were made indicate that the cows remain close to the calves before they join the moving bands. Occasionally a cow is not seen near a calf, but usually there is a possibility of the cow being in a position to watch it. Some observations made June 4, 1938, are a little different from most of those cited above. However, proximity of the road to the calves may have had some bearing on the actions of the elk in this case. I spent the day watching the behavior of antelope does immediately east of Trumpeter Lake. Near the top of a butte I noticed 2 elk calves lying about 2 yards apart. Although they had been there at least since 9 a. m. when I had begun to watch, I did not see them until 11 a. m. when 4 cows came on the slope below. Then one of the calves stood up, stepped around a bit and lay down again. One of the cows walked up within 50 yards of the calves, but after peering at them for a few minutes returned to feed with the 3 other cows. When the calf stood up all the cows as well as 3 antelope watched it. These cows left at 11:45 a. m. and I am not sure that the calves belonged to any of them. During the day the calves each stood up twice to my knowledge and possibly did so at other times when I was looking elsewhere. At 5:45 p. m. 3 cows appeared from over the rise to the north and fed slowly toward the calves, coming to them at 6:10 p. m. The calves came forward about 5 yards and met their respective mothers and nursed for 8 minutes. The third cow which appeared heavy with calf stood between the other two families, looking around. At 6:30, the three cows and two calves moved west and at 7 they reappeared and went down the east slope feeding. Although no cows were seen near the calves during the day, except the four below them in the morning, it is possible that the mothers were out of my sight over the ridge but within view of the calves. Also, the road passing near the base of the butte on which the calves were resting may have kept the cows away during the day.

The mother elk protects its calf vigorously and with courage. O. J. Murie saw a cow chase a dog which had accidentally come near the calf and miss the dog by inches when it struck. Some observations on the behavior of elk and coyotes in Yellowstone are set forth to show that coyotes are little tolerated near the calf. Sometimes even antelope and other cows are driven away from the vicinity of the calf.

On May 30 in the Horseshoe, a lone cow galloped 100 yards after another cow which was passing 30 or 40 yards distant.

On June 2, 1938, at the Buffalo Ranch, two different cows with calves were seen chasing another cow, and one chased two antelope. Usually the antelope are not molested in this way nor are other cows.

On May 27, 1938, on a flat along Slough Creek, a cow chased a coyote about 150 yards, following it with evident determination. Near the edge of the open flat, the cow made a small circle back of the coyote and pursued it across the flat again. The coyote dodged the cow two or three times and disappeared in a grove of cottonwoods along the creek.

June 1, 1938, on the upper part of the Buffalo Ranch, I observed three coyotes traveling loosely together over the open sagebrush range. There were antelope alone and in small bunches, and several single elk, each with a calf, standing out in the sagebrush. I first noticed the coyotes at 10 a. m. moving about 100 yards apart, stopping here and there on their way to investigate smells and occasionally to pounce on a mouse. The coyote in the lead came near a buck antelope which advanced toward it, circling up to within 15 yards and shaking his horns. The buck stopped and the coyote trotted on his way. Two of the coyotes reached a marsh and waded through the water which was about 6 inches deep. On the margin of the marsh at least one mouse was captured. The third coyote followed an old river bank a little to one side of its two companions. When it came within 60 yards of two doe antelope it circled around them. The antelope, which appeared heavy with young, watched the coyote part of the time it was passing around them and advanced toward it when it cut back to its original course after passing them. All three coyotes went down the flats about one-third of a mile. One of four separate elk standing in an area of closely browsed willows advanced about 100 yards toward the approaching coyotes and the three other cows moved forward a few yards. About 75 yards from the first elk, the coyotes, after tarrying a few minutes, reversed their direction and started weaving their way up the valley again along a course a few hundred yards nearer the edge of the woods. At one o'clock, after the coyotes had gone out of sight up the valley, the cow which had approached the coyotes walked about one-third of a mile and joined a calf that had been lying, as near as I could determine, about 30 yards to one side of the course taken by the three coyotes in passing up the valley. It is rather surprising that this cow did not become worried when she saw the coyotes pass so near her calf. The coyotes went out of my view at 12:15. Near the same spot 15 minutes later a band of eight antelope were seen advancing alertly toward a coyote. They followed it while it hunted mice, and then began to feed as it continued to hunt through the sagebrush. A cow elk looking over her back watched the coyote and, while it was still about 300 yards away, arose and walked toward it with ears cocked rigidly forward. Fifty yards from the coyote the elk started after it on a dead run, causing the coyote to exert itself to keep out of reach. The cow then lay down and was there 1-1/2 hours later when I again passed by. Apparently she had a calf near her. These coyotes seemed to be hunting mice primarily.

On June 2, 1938, I returned to the Buffalo Ranch and made some more observations. At 9:30 a. m. a lone cow was watching a coyote 200 yards away hunting mice. The cow walked toward it and when 15 or 20 yards distant she dashed after it, driving it to the north. The coyote continued about 250 yards farther and after hunting mice for 10 minutes, and rolling on the ground, returned in the general direction of the watchful cow, but to one side of it. The cow walked toward it and when within a few yards, made a rush, which the coyote easily avoided. The cow circled and made another run at it, chasing it once around in a small circle perhaps 10 yards in diameter. She then followed the coyote as it moved off again to the north. A half hour later the first cow was seen wandering up the gentle slope but in a few minutes returned at a fast walk after the coyote which was moving again southward. She then nuzzled her calf which had been lying near the spot where she had been resting and from which she had chased the coyote. The latter wandered off in the sagebrush where I lost sight of it.

The observations made indicate that the cows remain quite near the calves and that the mothers keep a close watch for coyotes and drive them away.

Figure 13— A calf elk that died at birth but was not yet deserted by the mother.
It forms potential carrion for coyotes.
Base of Hellroaring Slopes, May 24, 1938.

CALF SURVIVAL, 1937

CLASSIFIED counts were made of elk whenever an entire band could be counted in order to get some idea of the calf increase in proportion to the cows and yearlings. The figures are not extensive but represent a fair sample. The percentage increase of calves in various bands is uniform considering the great chance there is for variation. My calf ratio is higher than that obtained by Rush (1932) between 1928 and 1931, from counts during the months of January, February, March, and April. His figure, converted so as to be comparable, is 25 percent and mine is 41 percent. The lower percentage of calves recorded by Rush may in part be due to the fact that his counts were made during the winter period when a relatively higher mortality occurs among calves. Summer counts made by O. J. Murie (1935) in Teton National Forest just south of Yellowstone National Park resulted in 1,192 cows and 458 calves, or a calf increase of 38 percent.

Elk Calf Survival, 1937

THE high survival of calves in 1937 indicates that coyotes were not getting many. No good calf counts were made in 1938 but I suspect the crop was lower than in the previous year because of the hard winter of 1937—38, which resulted in the cows becoming abnormally thin and weak. Their condition was poor during the last months of the gestation period and during calving time.

Figure 14— A very young calf elk shows remarkable faith in hiding and allows itself to be handled.
Soon calves become less tolerant and run away when approached too closely.
Tower Falls, May 29, 1938.

STATUS OF ELK

The elk population in Yellowstone Park is unquestionably too large, resulting in a severely overbrowsed winter range. The depleted range is harmful to the elk but even more harmful to the deer, antelope, and bighorn over whose ranges the elk wander and with whom they compete directly for food. The elk herd could safely suffer a loss of two-thirds of the present number, with benefit to the other ungulates, the ranges in general, and to the elk themselves. In an effort to improve the situation a program of elk reduction was inaugurated by the National Park Service in the winter of 1934-35.

All available data indicate that the coyote is a minor factor in the status of elk. Although the latter on the big game winter range on the north side of the park make up the bulk of the winter food supply of the coyote, it is in the form of carrion and little if any predation on elk exists at this season. During the calving period a few youngsters may be eliminated by the coyote but the data indicate that the calves eaten probably are largely carrion. Since there are now too many elk on the winter range occasional coyote predation on the calves would not be harmful to the welfare of the elk population.

Figure 15— Elk cow slowly enticing calf less than 24 hours old away from aspen grove in which it was born.
Junction Butte, May 25, 1938.