Fig. 20. Caribou track in 2-inch snow; hind foot superimposed on track of front foot. Combined track about 153 by 127 mm. Camp Ridge, October 29, 1947.
A front hoof is a little broader as well as longer than a hind hoof ([fig. 24]). The extreme and average lengths of the front hoofs in five of my adult male specimens are 80-92 (85.2); of the hind hoofs, 74-84.5 (79.8). In an adult doe a front hoof measures 77; a hind hoof, 72.
Reference.—Banfield, 1951a: 19.
[ Swimming]
In their extensive and long-continued migrations over a territory composed in large part of lakes, ponds, and rivers, the Caribou have almost daily need, from June to October, of surmounting these barriers by swimming. The low temperature of the water seems to have no deterring effect on them. Yet it appears that some of the animals may fail in attempting the passages of wide waters. Charles Schweder spoke of finding a number of dead Caribou, including bucks as well as fawns, that had apparently succumbed in crossing a 4-mile-wide lake on the Thlewiaza River. (Or had they perhaps come to grief in some upstream rapid and finally been washed ashore on the lake?) Bones on the shore indicated that this sort of tragedy might be more or less of an annual occurrence. Perhaps some of the victims had been wounded or were otherwise in poor condition.
The buoyant, hollow hairs of a Caribou’s coat enable the swimming animal to keep almost the whole median dorsal line of its body perhaps 2 or 3 inches above the surface ([figs. 9], [12]). In a doe noticed on August 28 the lowest point on the top of the neck, just in front of the shoulders, was practically level with the surface, but elsewhere the dorsal line, from snout to tail, was out of the water. In both doe and fawn the head is held so high that the lower side of the snout at the tip does not touch the water; in the older bucks of the autumn, however, the weight of their antlers presses the head down until the lower side of the snout is frequently in contact with the water. The swimming position tilts the antlers backward until the basal portion is practically horizontal ([figs. 9], [12]). All ages and sexes, while swimming, hold the tail nearly erect; but the very tip (perhaps only the tuft of hairs) inclines toward the rear.
On October 30 tracks indicated that half a dozen Caribou had swum across Little River near its mouth, breaking through a 10-foot rim of ice on the near side. When a herd of 2,000 or 3,000 crossed Windy River during an October night about 1944, as reported by Charles Schweder, they broke three channels through the thin ice that covered the river.
Once Charles saw a buck cross the 100-yard-wide Nahiline Rapids on Kasmere River, where it drops about 40 feet in a quarter of a mile; yet the animal did not seem to be carried far downstream. When about 10 Caribou (mostly big bucks) crossed the Windy River at our camp on June 24, the last two, I noted, were pointing almost upstream in the 6- to 8-mile-per-hour current.
The usual formation in which a small number of Caribou cross a bay or a quiet stretch of river is a single file, but a larger band is likely to make the passage in several simultaneous files. The fawns, in particular, follow as closely as possible behind their mothers.