Grizzlies and Rodents
GrizzlyGround Squirrel Relationships
The Arctic ground squirrel is common over all open country in the park, from the lowlands to the tops of the sheep hills. It is plentiful year after year, apparently undergoing no marked cyclic changes. Perhaps this is due to the steady, heavy pressure on the species by bears, foxes, wolves, and Golden Eagles, a pressure that does not permit overpopulation and resulting die-offs (Fig. 53).
As a bear travels or moves along feeding on vegetation, he may surprise a squirrel and capture it before it can escape into a burrow. If the squirrel does manage to reach a burrow, the escape may be temporary for the bear will excavate, nearly always with success. When the bear happens to encounter a set of squirrel holes, he gives them a routine inspection with his nose, and if the scent indicates that the squirrel is at home, the bear begins to dig. Usually squirrels are dug out when the bear happens to encounter a promising set of burrows. But at times, chiefly in late summer and autumn, squirrels are hunted systematically. I have noted more squirrel hunting at this time than in early summer.
Considerable excavating usually is necessary before a squirrel is captured. The bear may dig into three or four entrances in a set of burrows and in at least one he may dig so deep that his shoulders are hidden from view. While excavating at one burrow entrance, he tries to keep a sharp watch on the other entrances, for he knows that the squirrel may emerge from any one of them. He is not always successful in capturing his prey; even after laboring for as long as half an hour he may give up the job as hopeless. Occasionally, a squirrel escapes from one set of holes and vanishes into another set a short distance away, and the bear must then begin to dig anew. The bear's luck varies. He may be successful in a series of diggings, or he may try several times without results.
In late May and early June bears may be especially fortunate in their digging and come upon a nest of young squirrels, but more often the reward is a single squirrel (Fig. 54).
Jarring of Sod Causes Squirrel to Emerge
In excavating a burrow the grizzly may use a single paw or both paws together. He may pull away loose soil in the burrow for a time, then with both front paws push down and pull on the sod at the edge of an excavation to make it cave in, thus making a bigger opening and more room for digging. This pushing action, given joltingly, frequently jars the earth enough to cause the squirrel to run from one of the holes and be caught. At times this jarring action is performed only to scare out the squirrel. As he jars, the bear keeps a sharp lookout for the squirrel, knowing that it may emerge. On a few occasions I have seen a grizzly jump with the forefeet, a kind of pouncing movement, several times during excavation of a ground squirrel burrow.
On 27 August 1963 I watched a mother bear digging for a squirrel on Sable Pass. She had not dug far when she began jarring the sod on the upper edge of her excavation. No effort to loosen the sod was made. She obviously was trying to frighten the squirrel enough to make it emerge, which it did after she had struck the sod with both paws five or six times. After eating the squirrel, the mother and one of her two yearlings moved away and out of sight of the second yearling which was left behind digging at another set of squirrel holes. The yearling dug for several minutes and finally captured a squirrelone of the few times I have seen a cub do so.
Mother Does Not Share Squirrels With Cubs
The cubs usually wait docilely for the mother to eat her squirrel, but not always. On 23 July 1959, when a mother captured a squirrel that had emerged from a set of holes where she had been digging, one of her two yearlings growled and cried while she consumed the squirrel. This complaining continued for a minute or so after she had finished eating.
In August 1969 I observed a mother with one spring cub hunt ground squirrels near Tattler Creek for several days. The female chased one ground squirrel to a burrow and began to excavate. The squirrel slipped away to another burrow and the female followed. As the mother resumed her digging, her cub chased another ground squirrel to the first burrow. Apparently this burrow was now plugged because the cub caught the squirrel. This rare moment of success was short-lived; the mother ran over, snatched the squirrel, and ate it as the cub watched somewhat disconsolately.
About One Hour Expended to Catch a Squirrel
On 21 September 1950 I discovered a mother bear almost buried in an excavation she was making trying to dig out a ground squirrel. She had been digging for some time, judging from the depth of the hole. Her two spring cubs, in the meantime, had wandered almost half a mile away. Even after I discovered these bears, the mother continued working at the excavation for 45 minutes. After digging a while, she would put her nose to the bottom of the hole to test the squirrel scent, then raise her head above the surface, mouth open and panting, and look to see if the intended prey were trying to escape from another entrance. A few times she made four or five jumps up the slope to make sure the squirrel was not escaping. She would stand on hind legs and look around before returning to the digging. She kept caving in the sod at the edge of the excavation, pulling loose large pieces, and pawing them out from the bottom of the hole. The sod and loose dirt flew between her hind legs or off to either side. Sometimes a chunk of earth or a rock would make a noise loud enough to startle her and she would turn quickly to look. This happened four or five times. After a while she was hidden completely in the hole. Once she came forth to sniff at other entrances and began to dig at one of them, continuing until half-buried before returning to the main excavation. The cubs returned and after resting sat up watching the mother. At last, from her deep hole, she managed to bring forth a squirrel. She bit off small pieces and chomped with a wide open mouth at each one. She chewed five or six pieces before the squirrel was eaten. I have seen bears swallow long, thick pieces of caribou tendon without chewing, perhaps because they were too tough, but squirrels usually are eaten in small pieces with much chewing. The cubs moved a little closer, but just sat and watched the mother dine. Before wandering away, the mother made some final sniffings into the large excavation. This bear had dug for about an hour before making the capture; usually a grizzly will give up before expending this much effort at a squirrel hole. The small result probably did not compensate for the energy expended. This incident is a record for digging time, but on another occasion I watched a bear dig for 40 minutes and he also had begun before I first saw him.
A Squirrel Escapes
On 31 August 1963 I discovered a bear digging for a squirrel that had taken refuge in a burrow leading under a large boulder about as high as the top of her back. Her eagerness indicated that the squirrel's scent was strong. Digging mostly from the upper side of the boulder, she would dig for a few seconds, then crane her neck to see if the squirrel was emerging on the other side. Sometimes she would try to look over the boulder and continue to dig, rather ineffectively, with one paw. After about 15 minutes, while the bear was intent on digging, the squirrel sped from the other side. When the bear looked up, the squirrel had crossed a draw and was part way up the other side. The bear galloped after the squirrel but it escaped into another set of holes. The bear dug briefly at five entrances to this hole then concentrated on one, working until only her hind quarters showed above the excavation. During this time I heard a loud bawling, and 75 yards off I saw a lone, impatient cub wandering back toward its mother from the other side of the slope. The mother dug for another 15 minutes, then stood looking over the valley, mouth open, before proceeding briefly with her digging. Farther down the slope, she ate a little horsetail, then wandered away into the gathering dusk. The squirrel was safe for one more day.
A Mother Intent on Her Squirrel Hunting
In 1963 the berry crop failed in the high country, so the bears were forced to rely more than usual on other foods. Ground squirrel hunting also seemed more prevalent that fall.
On 8 September 1963 a mother whose spring cub was so crippled that its hind foot was useless, left this offspring far behind when she went hunting. I first saw the cub alone, bawling steadily, and it disappeared into a canyon. Fifteen minutes later the mother, having gone up the canyon, came over a ridge and the cub was soon on her trail, still complaining. The mother galloped along, looking expectantly for ground squirrels. In a patch of willows she dug for some time. Once, she emerged from the willows, looked around for the squirrel, and returned to her digging. Five minutes later she dashed into the open again, this time chasing and capturing the ground squirrel.
Five days later this same mother was observed on Sable Pass about 3 miles farther south. She alternately walked, trotted, and galloped as she moved along on a contour, looking for ground squirrels. The cub was 200 yards behind, limping along on three legs. The mother showed no concern until she was about one-half mile ahead of the cub. Then she lay down on a knoll facing the direction from which she had come, but before the cub reached her, she was on her way again, once running 30 yards after a ground squirrel but missing it. The cub finally reached its mother and they both disappeared for 25 minutes behind a knoll. The mother reappeared and sniffed around for half an hour, digging at one burrow and exploring two others. The cub rested and licked his injured foot. It was an unfortunate time to be injured because the mother was traveling more than usual in her hunt for squirrels. She made several short runs with ears cocked. In one set of holes she dug deeply at four entrances, moving from one to the other, poking her nose into each one. While she was busy at this den, a second squirrel emerged some 30 yards below and made short runs up the slope until it glimpsed her, whereupon the squirrel scurried a few yards away and sat erect and perfectly still for 15 minutes. In the meantime, the grizzly captured the squirrel she was after and came a few steps down the slope, but fortunately for the second squirrel, she turned aside. The little animal scurried 15 yards to a hole without being seen.
The mother, still hunting for squirrels, returned to where I had first seen her. Later, the resting cub tried to follow her trail but could not find the beginning because it circled and criss-crossed near the excavated holes. The cub bawled as he searched and was soon circling off to one side, getting nowhere. Finally, he started up the slope and after climbing 200 or 300 yards, found his mother's trail. His crying ceased, for his most pressing worry had been relieved, but soon he was crying again. Eventually, he saw the mother digging for a squirrel, but as he came near, she was traveling again, doubling back over the same route to the base of Sable Mountain. The cub took a brief rest, then followed her trail, again crying bitterly. Later, the mother led the way over a low ridge as she headed for Tattler Creek.
Such eager, prolonged hunting of squirrels is unusual. I have often observed squirrel hunting in the autumn, but none with quite this degree of energy and drive. Moreover, I have never seen a mother show so little concern for her cub. Apparently she was accustomed to having her crippled cub lagging far behind and crying.
In 1969, another mother with one spring cub spent much of its time hunting squirrels in mid-August. Over 8 days I watched her capture seven ground squirrels, and she was alert constantly for opportunities.
A Mother has Unusually Good Luck
On 1 September 1959 I watched the mother of two yearlings dig out a squirrel from a snowy hillside. The mother jumped at the squirrel four or five times before capturing it, sometimes so vigorously that clouds of flying snow almost hid her from view. I watched as she hunted squirrels for 2 hours and 45 minutes, catching nine. The two yearlings followed along, resting while she dug. As usual, they did not share in the catch nor did they expect to do so. The mother's success varied from hole to hole. Once she chased a squirrel into a hole so shallow that excavation took only 2 or 3 minutes. With little digging, she secured two more squirrels but at the next hole she almost buried herself before reaching the squirrel.
A Family is Unsuccessful
One day in late August 1969, near Toklat, I watched for several hours as a mother with two yearlings traveled, occasionally digging for roots or ground squirrels. The female began digging at a ground squirrel burrow in a patch of low willows, and when the squirrel ran from the hole, all three bears pounced after it, at times almost colliding with one another. Despite their efforts, or perhaps because of their mutual interference, the squirrel escaped to another burrow. The mother and one cub each dug at a different entrance, and the second cub watched, but they soon gave up and moved on.
Ground squirrels recognize the grizzly as an enemy and utter loud, sharp warning signals when one is near. All squirrels in the neighborhood sit erect and join the warning chorus. Frequently, squirrels living at our camp warned us when bears, wolves, etc., were passing. Many false alarms seem quite authentic until one experiences the genuine alarm call, which is unmistakable. Although ground squirrels are only a small part of the bear's nourishment, they do add some meat to his diet and considerable interest to his daily living.
Hoary marmots frequently send forth loud, sharp warning whistles when they discover a bear, but they are rarely excavated from their secure burrows among rocks and cliffs. Just as humans find a marmot occasionally away from the protection of a burrow, I expect bears sometimes come upon one too far from a retreat to escape. On a few occasions I have observed a bear investigate a marmot den but I have never seen a bear trying to dig one out. Marmot remains were seldom found in grizzly scats. However, if a marmot denned away from rocks, excavation by a bear would be a danger. Perhaps the bear is one of the factors causing marmots to live among rocks (Fig. 55).
Seven species of voles and lemmings have been found in the park. In years when one or more of those species are plentiful, bears sometimes feed on them. Mice are a tidbit, and so also are the underground stores of roots and tubers cached by the hay mouse (Microtus gregalis). Among the plants represented in the caches are coltsfoot (Petasites), bumblebee plant (Pedicularis), horsetail (Equisetum), knotweed (Polygonum), and peavine (Hedysarum alpinum americanum), the species the bears dig for constantly.
A cache may contain 2 or 3 quarts or more of roots, sufficient to make the excavation worthwhile. These mouse caches also are known to the Eskimo. Porsild (1953) says that Eskimo ". . . rob the mice caches which they locate by means of a dog specially trained for the purpose." Bears find the root caches (and the mice) with their keen noses, and probably learn quickly that mice favor hummocks for their nests and caches.
In 1955, a year of mouse abundance, bears were observed frequently digging into hummocks to obtain mice or their stored roots and tubers. On 20 June, a mother and her two yearlings, after feeding for a time on the previous year's crop of crowberry and cranberry, moved up into an area of hummocks, and dug out one hummock after another, for over 2 hours. In the same year, on 9 July when green foods were available, a mother and yearling spent much time digging for mice. A few days later, 16 July, although feeding chiefly on green foods, a mother dug into several hummocks. On 11 June 1959, although mice were not especially abundant, I found some root caches exposed and eaten by bears. In 1907 (a good mouse year) Charles Sheldon (1930) observed the grizzly feeding extensively on mice. He describes observations made on 9 October as follows: "The bear, evidently scenting a mouse in a tunnel, would plunge its nose into the snow, its snout ploughing through, often as far as ten feet, until the mouse had gone down into its hole in the ground; then the bear would dig it out and catch it with a paw.
I have seen no evidence of predation on beaver by grizzlies in the park, and I have only two records of grizzlies feeding on beaver carcasses there. One carcass was known to be carrion, and the other probably was also. I have no observations suggesting bear predation on beavers, and it seems unlikely that beaver serve as anything other than an occasional taste of carrion for the bears.
I have no evidence of grizzlies killing porcupines or vice versa. However, occasionally there is contact and sometimes a grizzly is injured or a porcupine killed, but the latter is rare.
The grizzly usually avoids the porcupine. For example, on one occasion I saw a plodding porcupine approaching a feeding bear. The porcupine stopped a few yards away, the two looked at each other, and the bear watched while the porcupine, maintaining his dignity, turned slowly and detoured past the bear. Alfred Milotte reported a bear watching while a porcupine approached and climbed a tree. Once, I saw a female grizzly watching a porcupine waddling past only a few yards away. A big male standing next to the female did not even deign to look, and the porcupine, for his part, seemed unperturbed by the presence of the bears.
Occasionally, bears fail to take proper precautions when they are near a porcupine. A bear appeared once near park headquarters with several quills in its face. The bear was seen rubbing its head against a tree, apparently trying to get relief. At least two other bears were reported with a few quills in their noses (Fig. 56).
On 2 June 1959 I saw a young bear with a crippled front foot that caused him to limp. The track of the normal paw was a little over 5 inches wide, that of the injured foot, about 4 inches. This suggested an old injury. In digging roots only the normal paw was used. Two days later this bear was shot at a campground. The claws on the uninjured foot were worn down, probably due to excessive use in root digging, and the claws of the crippled foot were unusually long from lack of normal use in walking and digging. Examination showed a number of old porcupine quills buried deeply in the injured foot. There was considerable festering in the foot and under the shoulder blade on the same side. The bear was thin, so although the injury was not fatal, it was crippling.
On 27 May 1959 while watching a mother and two 2-year-old cubs at Milepost 28 along the Teklanika River, I noticed that one of the cubs limped. On 7 June I watched the family feeding on berries near Hogan Creek. A few times the lame cub lay on its back to chew at the injured foot. Its jaws bothered it too, for it chomped them, pawed at its face, and shook its head impatiently. I could not see the quills, but the action made it almost certain that this cub had tangled with a porcupine. The following day, when I saw the bears on a distant slope, the cripple was still limping. On 10 June these bears were digging roots on flats near Sanctuary River. The cripple rested much of the time, once for 25 minutes, while the other two fed. When it walked, the injured foot was carried or used lightly. Sometimes it rested on the elbow instead of on the injured paw as it dug roots with the other paw. When I saw these bears on 11 June, the cripple was resting while the other two dug roots. The cripple obviously was not eating as much as its twin, and appeared gaunt. Its condition suggested that it might not survive the coming hibernation period.
On 25 June 1964, a photographer told me that he had seen a blond grizzly "explode" out of a patch of willows and that a few minutes later a porcupine emerged on the opposite side. When I arrived at the scene, I saw the bear on the slope biting at his paw.
Isabelle and Sam Woolcock reported watching a young bear jumping playfully about a porcupine. The bear seemed to understand that the porcupine was not to be touched; nevertheless, there was a chance for an accident. The porcupine climbed a stout willow where I saw it an hour later.
Some cubs may learn about porcupines by observing the behavior of their mothers, and others may learn from experiences. Incidents similar to the one told about a black bear also may occur to grizzlies.
Species other than bears sometimes are indiscreet about the porcupine. Foxes have been found injured seriously by quills, and unsophisticated dogs are stuck frequently by quills. In No Room in the Ark, Alan Moorehead (1959) writes about superannuated lions: "Often in their extremity old lions pounce on a porcupine, and that leaves them lame with a mass of quills in their paws."
It also is possible that the porcupine contributes to the improvement of the bear's habitat. At a spot near the Toklat River porcupines have killed most of a patch of spruce, and consequently willow brush and horsetail a favorite grizzly food have increased. In June, grizzlies feed extensively on horsetail in this patch of dead spruces. One day I collected 12 fresh bear scats in a few minutes, all containing only horsetail.
Last Updated: 06-Dec-2007