The information on the food habits of foxes was largely secured by the analysis of scats. In the summer months most of them were gathered at eight fox dens; in winter they were picked up along the roads and trails. It is felt that sufficient data were secured to give a satisfactory picture of the food habits under existing conditions. Snowshoe hares were extremely scarce where the scats were gathered so consequently there were few remains of hares. If the hares had been numerous they would no doubt have been well represented in the diet.
TABLE 18. Classification of 827 summer food items found in 662 red fox scats gathered in Mount McKinley National Park from June 1 to October 1 in 1939, 1940, and 1941.
TABLE 19. Classification of 178 winter food items found in 124 red fox scats gathered in Mount McKinley National Park between October 2 and May 31 in 1939, 1940, and 1941.
Discussion of Food Items
Field Mice.Four species of Microtus, a Lemmus, and a Clethrionomys are available to the fox. At least some of the species are subject to definite cyclic fluctuations. In 1938 mice were extremely abundant; rangers reported seeing them frequently scurrying about in the open. They died off in large numbers sometime during the winter of 1938-39 so were quite scarce in the late spring of 1939. In 1940 and 1941 mice were more plentiful than in 1939 but had not by any means reached a peak of abundance. They were common enough, however, to furnish good hunting for the foxes. Species of the genus Microtus were most abundant.
Mice were found in 415 or in almost two-thirds of the summer scats. In some of them, remains of two or three mice were found, but generally remains of only one mouse were identified. Most of these scats were gathered at various dens so that the majority of them were from pups. Possibly the diet of adult foxes includes an even higher proportion of mice than does the diet of pups, since odd mice captured while hunting for the pups probably are eaten more often than ground squirrels. Parent foxes seemed to prefer to carry to their pups the bulkier ground squirrels rather than the much smaller mice. Such a practice would be efficient.
The scats gathered in 1939 when mice were scarcest showed a predominance of mice in the diet. This may be due to the location of the den at which the majority of the 1939 scats were gathered. It was in a grove of trees at Teklanika Forks, surrounded by flats, where ground squirrels were less abundant than they were near the other dens located on mountain slopes and passes. Even though mice were scarce at the 1939 den they may have been more conveniently secured than ground squirrels.
During the winter and in the absence of hares, mice usually form the staple diet. Meadow mice are easily captured even when their activity is carried on under moderate depths of snow. The fox locates the mouse by scent or hearing, then pounces so as to break through the snow directly over the mouse and pin it down. Even if the first pounce fails it may block runways so that escape is shut off and the mouse is captured in the ensuing scramble.
Ground Squirrel.Ground squirrels are abundant and much used. They hibernate in winter but are obtainable from April to October. Their remains were found in 307 of the 662 summer scats.
On June 17, 1941, a silver fox was seen moving steathily along a ditch beside a road, hunting for squirrels. At intervals he stopped to look. Meanwhile, the squirrels from surrounding points were calling sharply and disappearing into their holes as he neared them. After moving along slowly with no success, the fox made a quick dash of 200 yards through some hummocks, apparently to get into new territory where his presence was not widely advertised. After making this long spurt he stood still, watching, then moved out of my view among the hummocks. When hunting mice, no attempt is made to hide, but while hunting ground squirrels the fox keeps hidden as much as possible.
On July 2, 1941, this same silver fox was again observed hunting. He captured three mice in 10 or 15 minutes. I then had to leave, but when I returned an hour later the fox was carrying a ground squirrel. Three times he laid it down in order to pounce for mice. Once he lay watching a hummock for several minutes waiting for a mouse to come out. Then, weary of waiting he picked up his ground squirrel and trotted homeward.
A fox appeared at the Mount Eielson tent camp and quickly captured three of the ground squirrels which had been tamed by feeding (a good example of one effect of domestication). After catching the three squirrels he piled them so that the second squirrel crossed the first, and the third crossed the second. Then he seized all three where they crossed each other and left for his den with the heavy burden.
On October 14, 1939, a red fox appeared at our cabin looking for food scraps. He was about to feed on some morsels we had tossed to him when he suddenly turned, crouched, ran forward a few steps, and pounced. We did not know what he had pounced upon until he lifted his catchour pet ground squirrel which had not been out of its burrow for several days and this day was probably taking its last look around before the long winter's sleep. My assistant and I looked at each other open-mouthed, and then Emmet said, "Well, that's Nature."
The fox with this treasure would not trust us so galloped away to feed in security.
Once a fox chased a ground squirrel into a hole and spent considerable time digging for it. Another fox ran for 15 yards and pounced at a ground squirrel but missed him. He put so much energy into his pounce that he rolled over. As this fox continued on his way the squirrels in the neighborhood sat on their hind legs and scolded him loudly, and sparrows darted at him.
Hoary Marmot.Remains of marmot were found in four scats only.
Porcupine.Porcupine remains were found in four summer scats and one winter scat.
John Colvin and Lee Swisher, trappers along the north boundary of the park, both told me that on skinning foxes they frequently found porcupine quills lying against the inner side of the hide. One fox trapped by Swisher had festered sores over its throat and shoulders caused by the presence of numerous quills. Swisher once found the remains of two or three porcupines at a fox den. A road crew once captured a half grown fox at Savage River with eight or nine quills in its face. The fox was weak and easily run down but after the quills were removed it regained its strength in a few days.
Like the coyote and wolf, it appears that foxes occasionally kill porcupines.
Snowshoe Hare.Remains of snowshoe hare were found in only one scat, but hares were extremely scarce in the region studied. Dixon (1938, p. 161) found remains of 25 hares at a single den at a time when hares were abundant. Hares are no doubt an important food when they are available.
Cony.Remains of cony (Ochotona collaris) were found in but one scat. The cony is probably rarely captured.
Caribou.Remains of adults and calves were found in 20 scats. Probably all caribou eaten is carrion, although on rare occasions I suppose a very young calf might be killed. I have no record of such predation, however.
Dall Sheep.Adult remains were found in 34 scats. Leg bones were found at one den. Sheep are frequently eaten as carrion.
Remains, representing at least three lambs, were found in 11 scats. It is of interest to note that lamb remains were found only in the 1939 scats, the year that the wolves preyed to some extent on lambs. This suggests that foxes were feeding on what the wolves left.
Shrew.Although very abundant, no shrews (Sorex sp.) were found in any of the scats. A dead one, uneaten, was found at one of the dens. In Michigan I found that foxes often killed shrews but scarcely ever ate them (Murie, 1935).
Birds.Ptarmigan remains were identified in only one scat but some of the remains classified only as "bird" may have been ptarmigan. Feathers of ptarmigan were found at one den. On May 15, 1939, a fox was seen carrying a female willow ptarmigan it had just captured. After playing with it, he ate most of it, then carried the remainder off through the woods. While he fed, some magpies watched from the willows, and two or three gulls, attracted by the kill, lit on a nearby gravel bar. During the course of the study willow ptarmigan were relatively scarce, especially near the particular dens studied. This accounts for the few remains in the scats. At a time when ptarmigan were abundant, Dixon (1938, p. 161) reports finding remains of 20, mainly males, at a den.
Small birds are picked up incidentally. Several of the scats contained remains of small birds, two of which were identified as sparrows. At one den a pup captured a nestling sparrow which fluttered on the ground nearby.
Egg shells were found in two scats at one of the dens. The shells possibly were those of ptarmigan eggs.
Snails.Traces of snails were found in two scats.
Wasp.Wasps were found in six scats. There were at least five wasps in one of the scats.
Blueberry.Blueberries were found in 52 of 124 scats picked up in winter and in 8 of the summer scats. The volume of blueberries in these scats generally varied from 50 to 100 percent of the contents. Blueberries are common over the fox range and are a highly important winter food. They began to appear in the droppings as early as September 13, and the foxes fed on them throughout the winter and into April. Mice during this time were present in moderate numbers. When foxes were first noted feeding on this berry, mice were available in sufficient quantity to furnish the foxes food, which would indicate that they are especially fond of blueberries. But no doubt the blueberries are at times eaten from necessity. Lee Swisher said that in the winter of 1939-40, when mice were scarce, foxes were living almost entirely on blueberries. They dug down through the snow for the berries lying on the ground. That winter, probably because of the scarcity of mice, foxes captured in traps were eaten more than usual by other foxes.
Bearberry.One fresh dropping picked up in February, and two collected in March, contained mainly bearberries. This plant is not abundant in the park.