Fauna Series No. 4

Fauna of the National Parks — No. 4 Ecology of the Coyote in the Yellowstone

CHAPTER II:
POPULATION AND MORTALITY

COYOTE MORTALITY AND NATURAL CONTROLS

NATURAL CONTROL of populations is a subject on which we do not have much information, especially in the case of carnivores, and it is a question which is at present receiving much attention. Before the white man interfered we know that controls existed, and although there were cycles of abundance and scarcity among many forms, there appeared to be large numbers of predators and prey species coexistent over extended periods. According to mathematics, any species could flood the world in a short time if unchecked. What are the checks?

In Yellowstone, after 4 years of absence of artificial control, it is apparent that coyotes have not multiplied according to mathematical expectation. The evidence shows that the population spread has been very limited and has been only into areas adjacent to the park boundaries. As I mentioned before, several rangers and naturalists in Yellowstone have been interviewed and most of them believe that the coyote population has not greatly changed during the last 4 years. Some felt that there may have been even fewer coyotes in 1938 than in immediately previous years. They were more plentiful in some areas, such as the Game Ranch area, in the winter of 1938—39, but were reported scarcer around Mammoth, suggesting a compensatory local shift in population.

My own impression, based on coyotes seen and frequency of droppings in the trails, is that the 1938 coyote population was quite similar to that of 1937. There is no good way of measuring coyote abundance and we can make only rough estimates of the comparative sizes of populations from year to year. At any rate, coyote numbers seem to be remaining rather stable and not pyramiding.

To determine mortality statistics and causes for an elusive animal such as the coyote is a difficult task. Dead animals are not easily found in a wide expanse of country, so that even though quite a number of coyotes may be dying on the range each year one would not expect to find many, or even any, of them. Discovery of a carcass or what is left of it is largely a matter of chance. It was, therefore, not expected that records of many dead coyotes would come to my attention. The number that did come to light suggests that quite a number of coyotes are dying each year.

Fourteen dead coyotes were recorded in the winter of 1936—37, 10 in the winter of 1937—38, and 3 in 1938—39. Data for the last year are probably incomplete since I had spent only about 10 days in the field. These observations were made during the latter part of February and early March, and were discontinued at that time because of other duties. In addition to actual deaths, a number of sick animals were observed. The percentage of dead coyotes found was naturally small.

The causes of death could not be determined with absolute certainty, but in the following discussion the incidents are grouped in accordance with apparent symptoms. These suggested two general causes—starvation and disease. It should be kept in mind that this grouping is entirely tentative, that successful diagnosis has not been accomplished, and that much remains to be done.

Figure 1.— Coyotes in a weakened condition, unable to run away, found at Tower Falls in February 1937, by Ranger David D. Condon.
Photo by D. D. Condon, February 1937.

Starvation.—In February 1937 Ranger Dave Condon found four coyotes at Tower Falls which were apparently starving. Condon states in his report for that month: "On the eighth a coyote was found at Yancey's ranch practically starved. On the ninth another was caught near the Yellowstone River Bridge, and on the tenth one was found near the station at Tower Falls. Two of the animals died before they were taken to Mammoth, the other was killed in Mammoth, and all were found to have been Starving."

Dr. Howard Welch of the Montana Veterinary Research Laboratory of Bozeman, Mont., examined one of these coyotes and found no evidence of disease or parasites. A fourth coyote was collected and examined by Raymond West but no cause other than starvation could be found to account for the poor condition of the animal. These coyotes were so weak that they were run down on foot within 60 yards. Condon reported that coyotes in general were in very poor condition in January. It was thought that the starving animals were young.

Conditions during the winter of 1936—37 were unfavorable to the coyote, for the snow was so loose that these animals had difficulty in traveling through it. On the other hand, the loose snow was only a slight hindrance to the mobility of the game animals in their search for food and they came through the winter in good condition. It is of significance that of 28 bighorn lambs wintering on Junction Butte only a single loss was reported by Condon. There were several deer at Tower Falls that apparently were not molested by the coyotes. Condon stated to me that the coyotes had great respect for the deer. When coyotes approached the deer, the hair on the backs of the latter raised as they assumed a threatening attitude and the coyotes retreated. The coyotes appeared to be actually starving in the midst of deer and bighorn.

The caretaker at Canyon stated that two coyotes had starved there during that winter.

Coyotes were reported to have been starving at Slough Creek and at the Buffalo Ranch. Coyote remains were found in eight scats at one of the haystacks at the Buffalo Ranch. The animal eaten may have been one of those that died of starvation. It seems probable that coyotes were starving in every part of the park during the winter. Trappers at the edge of the park in the Jardine-Gardiner area told me that the coyotes taken in the winter of 1936—37 were all extremely thin.

Remains of seven other coyotes which had died of unknown causes during the winter of 1936—37 were found. Some of these may have perished from starvation. Near the mouth of Elk Creek the remains of a large coyote which had probably died in April was examined on May 7. As the tips of all four canines were worn flat, the animal was undoubtedly an old one.

On May 11 at Yellowstone Lake I examined a coyote which had been found dead under one of the buildings. It was a female with well worn canines. There were no embryos. The animal was exceedingly emaciated, weighed only 13-3/4 pounds, and had an empty stomach. Near the hip bone was a suppurated lesion about 1 inch in diameter, which may have been a contributory cause of death.

On May 13 at the base of Specimen Ridge opposite Trumpeter Lake I found fur remains and the tip of the tail of a coyote that had died during the winter. This location is not far from Junction Butte where the bighorns were wintering.

On June 15 near Madison Junction remains of a coyote were seen in a coyote dropping, indicating that one had died in the vicinity.

On July 4 a coyote skeleton with some flesh and hide still attached was observed near Yancey's.

A coyote dropping was noted at Swan Lake and another above Oxbow Creek containing coyote hair.

Snow conditions during the winter of 1937—38, in contrast to those of the previous winter, were favorable to the coyotes in that heavy crusts made travel for them easy. Nevertheless, the remains of 10 coyote carcasses were found. Four of them were located where food was plentiful, but the remains of the other six were found in areas where food was scarce, so that these animals might have become weak and died from food shortage. On the north side of the park, deer, and especially elk carrion, was abundant because of the heavy winter kill among these species. As food in this area was readily available to the coyotes, starvation was not a mortality factor on the elk winter range.

Mrs. Margaret Gary (Yellowstone Nature Notes, March—April 1938, p. 18) reported finding two dead coyotes near the South Entrance and Ranger Tom Gary told me that later a third was found there. One of these was found January 27, 1938, one on February 26, 1938, and the third later. All were very thin and their stomachs were empty. Numerous porcupine quills were found in the throat and over the body of one of them. Very little big game winters in this area, hence there would be little available carrion. As the deep snows make mousing difficult and the snowshoe hare is not abundant, starvation in this case was likely.

Rangers Lee Coleman and Robert Beal found a dead coyote at the Thorofare Station on the Upper Yellowstone which may also have starved.

On April 13 Rangers Lee Coleman and Walter Gammill brought me a coyote carcass which they had found on upper Slough Creek. It was very thin, weighing only 13-1/2 pounds, and the stomach was empty. Since not many elk wintered on upper Slough Creek the latter part of the winter, there would be but little carrion available. This coyote also may have starved.

In June a dropping in Pelican Meadows contained a mass of coyote hair. This is not a clear case and the condition of the dead animal that had served as food is of course unknown, but starvation during the winter in this particular locality is a possibility.

On February 26, 1939, Ranger Condon captured a thin, weak coyote at Yellowstone Lake. This animal might have been starving. In addition to these more recent records, Ranger John Jay said that about 1932 he and Ranger Al Elliott had captured a weak coyote at Yellowstone Lake.

Figure 2.— Female coyote found dead under a building at Yellowstone Lake. This emaciated animal weighed only 13-3/4 pounds and had an ulcerated sore on its back.
Yellowstone Lake, May 11, 1937.

Starvation as a population control.—All the foregoing cases are characterized by extreme emaciation and the absence of any bodily evidence of specific disease or parasites (facilities for bacteriological examinations were lacking). Furthermore, they appeared to be associated with food scarcity. In view of these facts, starvation may have been the cause of death.

Food scarcity may operate in two ways to control coyotes: through death of individuals and through reduced reproduction. It has been thought that in the classic case of the lynx-rabbit cycles in the far north not only do many lynx starve during times of rabbit "lows," but many of the survivors fail to breed. It is generally recognized that reproduction is affected in varying degrees by food shortage or by an unbalanced diet. Hamlett (1938) states that female coyotes come into heat for only a short period and that the occurrence of two heat periods in the same year is doubtful. This would make it possible for a short period of starvation to sharply affect reproduction if this period should coincide with the breeding time. Thus winters unfavorable to coyotes may be followed by a decrease in number and size of litters.

Starvation among other carnivores is not unknown. The lynx has already been mentioned. In the Arctic regions the white fox is known to starve during certain winters and in some sections native trappers scrutinize the apparent crop of mice and lemmings in the fall, attempting to anticipate the probable harvest of fox furs for the coming season.

O. J. Murie has informed me that in the winter of 1914—15, during an expedition in Hudson Bay, there was a decided die-off of white foxes. Frequently little piles of white fur and the tail were found in the spring which, according to the Eskimos, were the remains of starved foxes that had been consumed by survivors. Two dead foxes, both greatly emaciated and one of them partly eaten by a raven, were found. Incidentally, field mice and lemmings were so scarce that it was with difficulty that a few were obtained for specimens.

Such conditions are, after all, comparable with those observed among the coyotes in Yellowstone.

Figure 3.— A coyote brought in sick, but after a week of feeding largely recovered and was set free.
Tower Lake, September 2, 1937.

Disease.—It is, of course, possible that some of the coyotes which seemed to have been starving may have died primarily from disease. At any rate, in addition to the cases of apparent starvation there were others clearly involving disease.

On August 26, 1937, a sick coyote was captured near Tower Falls and kept in the barn for more than a week. It appeared dazed, lay down most of the time, but occasionally stood up and turned in a circle. When I saw it on September 2 it was much better, although it had not recovered sufficiently to be wild and was still readily handled. It ate a large quantity of meat, there seeming to be no limit to its capacity. At this time the animal limped on a front foot and acted as though it had received a severe blow on the head. It may have been hit by an automobile.

Ranger Condon informed me that one of the tame coyotes at Tower Falls during the winter of 1936—37 was frequently seen jerking its head downward, and that in the winter of 1938—39 he had seen a coyote at the Mammoth dump and one near Gardiner with the same jerky movements of the head. Such nervous movements are characteristic in a number of diseases.

On September 28, 1937, at Gibbon Meadows I watched a coyote, apparently a pup, which acted abnormally. During the 10-minute period that I watched it hunting mice and grasshoppers it frequently shook its head and sometimes also its body. The shaking was done repeatedly as though it were trying to rid itself of some discomfort. It happened to trot into the woods where I was standing and ran off rapidly upon seeing me. Assistant Park Naturalist Oberhansley, in Yellowstone Nature Notes (November—December 1937), reports finding a sick coyote in Gibbon Meadows on October 11. This was about 2 weeks after I had noted at the same place the distressed coyote previously described; possibly it was the same animal in a later stage of some disease. Oberhansley stated that the coyote would alternately lift one hind leg and then the other, jerking them rythmically forward and upward.

It was suggested that the action resembled the early throes of distemper. When the coyote ran, Oberhansley was easily able to keep up with it, and when pursuit was stopped the coyote walked about 10 feet and lay down on its side, panting. When approached, it fled again in an awkward manner, its hind legs failing to "track." Finally, when cornered on the bank of the Gibbon River, it laboriously swam the stream and stood on the opposite bank, the hind legs alternately jerking spasmodically. Oberhansley suggests that since dogs are kept at campgrounds the coyotes that visit those areas could easily pick up a distemper infection from them.

On September 9, 1938, a bus driver picked up a coyote pup near Sheepeater Cliff and brought it to Canyon where Temporary Ranger Jean Young took charge of it. Young stated that the animal was extremely thin and too weak to stand. It made convulsive jerks, especially in the rear quarters. For 2 days it would not eat, but on the third day it was induced to take some milk, with apparent relish; later it was fed gravy with a little cod liver oil. Its appetite became ravenous and it improved rapidly in every respect, finally becoming too strong to handle readily. It was released on September 17, still retaining a slight twitch in the hind legs.

If the coyote had not been nursed it would doubtless have died, having been too weak to seek food. The incident suggests that starvation is an important secondary cause of death in animals which must spend some effort in gaining a livelihood. A slight ailment may cause disinclination to hunt and a consequent period of fasting, which, if continued for several days, may have a cumulative weakening effect. Eventually the animal, primarily due to lack of food, becomes physically unable to hunt and dies. Such an animal on the other hand, if fed, might readily recover. Since the coyote nursed at Canyon apparently had not fully recovered as indicated by the persistence of the twitch in the hind leg, it is possible that, when it returned to the woods, it again became weak.

Three of the dead coyotes reported during the winter of 1937—38 may have died from disease. At the Daisy Geyser in the Old Faithful area, where food is usually available, remains of a coyote were found in June by a temporary naturalist.

On February 9, in a patch of willows along the Gardiner River near Mammoth, I came upon six coyotes which had been feeding on another one and had cleaned it up except for one hind quarter. Most of the ribs had been consumed and the skin had largely been removed from the skull. This coyote had died during the day, for rigor mortis had not yet set in. On February 13 the skull of a coyote which had died rather recently was found along the Gardiner River. The teeth were much worn. These two coyotes could not have been starving, for food in this area was readily available at the Mammoth and Gardiner dumps in the form of carrion.

In the spring of 1938 Ranger Rudolf Grimm found the remains of a coyote near the Game Ranch, where food was plentiful. This one, too, may have died of disease.

Below Deckers Flat, a few hundred yards from the park boundary, a trapper during the winter of 1937—38 found two thin coyotes which showed no evidence of any wounds. These animals may have died from disease for a number of elk carcasses strewn over the area excludes the possibility that there was a food shortage.

During the winter of 1938—39 Assistant Naturalist Oberhansley followed the tracks of a coyote in the Mammoth area to the place where the animal had curled up in the snow and died. When he found the carcass it had been partially consumed by another coyote. In the same area he found the fur remains of another coyote, and saw a weak, thin one that had been lying at the edge of one of the hot pools. Since food was not scarce these animals, too, were probably diseased.

In the fall of 1938 coyotes were noted dying of disease in Jackson Hole. On October 5, O. J. Murie examined a dead coyote on the Elk Refuge. Workmen had found it very thin and weak on October 2, and had killed it with a stone. The cause of its weakness could not be determined, but at this time of year food was abundant. Early in September a guide found a small emaciated coyote up the Gros Ventre River. He fed it, and, feeling sorry for it, put a coat around it that night. Next morning it was dead. On October 7, O. J. Murie examined a dead coyote which had evidently been sick. A local resident had killed it the previous day with a rock. The lips and mouth of the weakened animal were encrusted with numerous wartlike growths. This same man had seen three other coyotes during October that appeared sick. He had not killed them, although his dog had been able to catch up with them easily and "stop them." It may be of some significance that in parts of Jackson Hole coyotes were scarce in the winter of 1938—39. South of the park, in the Pacific Creek drainage, no coyote tracks were noted by Rangers Condon and Gilbert on a trip made in February. Possibly the diseased animals noted in the fall were only a portion of a larger number of affected animals in Jackson Hole. One of the animals trapped there in the winter by one of the residents also had the wartlike growths about the mouth, but the general condition of the animal was not learned.

An abnormal coyote was also noted in the winter of 1935—36 in the Jackson Hole region. Two local wardens were going up the Gros Ventre River when they came upon it feeding at an elk carcass. Their dog had run up quite near the animal but was called back. One of them shot at the coyote but missed, and it did not even flinch. After a moment the coyote happened to turn and saw the two men. Then it became apparent that one side of the animal was almost bare of fur and that it had a nervous movement, repeatedly "bowing," as one of the wardens expressed it. As it departed, one front leg seemed useless and a hind leg partially so as if paralyzed. Since the fur was not good the men did not shoot it. They concluded that the coyote was diseased and stone deaf.

Diseased coyotes and wolves are occasionally mentioned in the literature pertaining to them. Bailey (1926, p. 151) quotes the following observations taken from the journals of Alexander Henry: "A large wolf came into my tent three times, and always escaped a shot. Next day, while hunting, I found him dead about a mile from the fort; he was very lean and covered with scab."

Warburton Pike in Barren Ground of Northern Canada, p. 52—53, writes about wolves: "I saw only wolves of two colors, white and black, during my stay in the North, although I heard much talk of grey wolves. There was some sort of disease, resembling mange, among them in the winter of 1889—90, which had the effect of taking off all their hair, and, judging from the number of dead that were lying about, must have considerably thinned their numbers."

Probably disease has always affected coyote populations periodically, just as in the case of game species, hares, lynx, foxes, and other animal forms. Disease, and possibly also starvation at times, operate most effectively when the population is large.

Mortality due to porcupine quills.—When opportunity offers, coyotes prey regularly on porcupines. It is reported by rangers that during the period when control of coyotes was practiced in Yellowstone a large number of them carried porcupine quills. Generally the presence of the quills had no deleterious effect. Often they were lodged no deeper than immediately under the skin. It is conceivable, however, that occasionally a coyote may become so impregnated with spines as to eventually cause death, and there is some evidence to that effect. Under "Brevities" (Yellowstone Nature Notes, October 1929) the following incident is given which shows that a coyote had been rather seriously "stuck up" by a porcupine. A Mr. Fisher of the park transportation company had found a coyote "with more quills in his mouth than the ordinary porcupine has in his body." He approached within 5 feet of the animal, and could have easily killed it with a club, for the coyote was more interested in extracting the tiny barbs than he was in the presence of the man.

O. J. Murie (1935, p. 12) gives the following incident: "That the coyote does not always fare so well is indicated by an experience related by Forest Ranger Jack Tevebaugh, who was stationed in the Upper Yellowstone in the winter of 1930—31. In the latter part of March he shot a coyote that was extremely emaciated. It was found to be full of porcupine quills, in the skin, in the tissues under the skin, on the head, and even inside the mouth. On the head were two festering sores."

When food is scarce the coyotes probably are less circumspect in their attacks on porcupines, and suffer more severely from the quills.

Attacks by elk and other ungulates.—Coyotes as a rule are too quick to be caught under the stabbing hoofs of an elk or a deer, but fatalities of this kind have occurred. E. J. Sawyer (Yellowstone Nature Notes, February 1927) reports an observation made by Ranger Bruce between Mammoth and Blacktail in which an elk had apparently killed a coyote. The dead coyote, badly mutilated and with a broken back, was found in the midst of a much trampled area in the snow, over which blood and hair were scattered. Tracks showed that it was an elk that had killed the animal.

Ranger Clifford Anderson at the Game Ranch on April 27, 1931, found a dead deer and dead coyote lying side by side. There was no mention in his report concerning the conditions of the animals or the cause of death.

On February 9, 1938, I watched a doe deer nearly strike a coyote. She kept reaching out for it with striking front feet and the coyote dodged the sharp hoofs only by great effort.

The trapper.—In modern times it is necessary to add the trapper to the list of controls of coyote populations, even in the case of a national park. While it is true that the Yellowstone coyote population is essentially a self-contained unit, subject to the ecological influences felt by such animal units, nevertheless it is not entirely contained within the political boundaries. Observations mentioned previously show that some coyotes go outside the park, probably for limited distances, but nevertheless far enough to become available to trappers in the vicinity who gladly take advantage of this occasional surplus of fur supply. As stated previously, many trappers who were interviewed expressed the hope that the National Park Service would not control coyotes so that they might have the opportunity to capitalize on the occasional surplus. Trapping is a small but persistent drain on the Yellowstone coyote population.

Last Modified: Thurs, Dec 20 2001 10:00:00 pm PDT
http://www.cr.nps.gov/history/online_books/fauna4/fauna2b.htm