| Species | Ten piles of cuttings | Frequency of occurrence | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Agropyron repens | 1 | 0 | 0 | 2 | 0 | 0 | 6 | 19 | 0 | 4 | 13 |
| Poa annua | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 00 |
| Bromus carinatus | 0 | 0 | 0 | 0 | 0 | 10 | 0 | 0 | 0 | 0 | 04 |
| Bromus inermis | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 00 |
| Medicago sativa | 40 | 14 | 30 | 30 | 31 | 5 | 0 | 0 | 21 | 4 | 73 |
| Lepidium densiflorum | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 00 |
| Galium aparine | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 01 |
| Lactuca scariola | 6 | 2 | 1 | 2 | 5 | 0 | 0 | 0 | 2 | 4 | 09 |
[A] Analysis made on May 12, 1946, on an area 20 × 80 yards, at Lawrence, Kansas.
[B] Each of the first ten vertical columns gives the composition of one pile of cuttings. The last column gives the percentage of occurrence in the piles of cuttings of each species of plant in the area. Place and date for data in table 2 same as for table 1.
Approximately one out of every ten voles caught in snap traps had a piece of plant in its mouth. Occasionally a vole took a piece of food into a live trap. Evidently the food is not always eaten where it is procured. Grasses of the genus Poa are the kinds most frequently found in the mouths of dead voles. Bromus carinatus, B. inermis and sweet clover (Melilotus alba) were found in the runways. The pulpy fruit of the horse nettle (Solanum carolinense) was found partly eaten, especially near the entrances to underground passages.
Food Caches
Caches of seeds and underground parts of plants are stored in subterranean chambers. One lot of food was found stored on the surface of the ground. Four times, piles of seeds in runways indicated the species of plants which the voles were storing.
One underground cache was found on May 27, 1946, on the University campus, by John Evans, Richard Edgar, and the writer. This cache was in a large chamber in a tunnel system of the prairie vole, on an east-facing hillside of walnut trees, catalpas, and Kentucky coffee trees. The oval chamber was 250 mm. wide, 400 mm. long, and 200 mm. high. The roof, at its highest point, was 30 mm. below the surface of the ground. There were two entrances to the cavity, both on the downhill side. The cache consisted of eight quarts of seeds (approximately 2,800) of the Kentucky coffee tree (Gymnocladus dioica). The seeds were packed with earth and all were well preserved. The site of this cache was in an area which was shaded by a small coffee tree. A seed of this tree is spheroidal, measures 17 mm. in width, and weighs 2 grams.
Several times in the fall of 1945, in the above-mentioned grove, the writer found pods of the coffee tree lying in the runs of the voles. These pods were sometimes entire, but more often they had been gnawed; frequently only part of a pod remained, indicating that the voles were storing or feeding upon the seeds, although the possibility that the mice were storing food did not occur to the writer at the time. Three times, seeds of other plants were found piled at the entrances of the burrows of voles. Twice these piles consisted of from 50 to 70 seeds of the common dandelion (Taraxacum officinale). The third pile was composed of 20 seeds of the giant ragweed (Ambrosia trifida).
A pasture of Canadian bluegrass (Poa compressa), wild millet (Echinochloa crusgalli), sedges (Scirpus spp.), and clover (Trifolium sp.) in Atchison County, Kansas, was examined in November, 1945. This area was the home of a dense population of prairie voles. Wherever a path of the voles crossed a deep imprint of a horse's hoof, there was a collection of cuttings from the horizontal stems of the clover which bordered the runways. Some of the cuttings may have been made by lemming mice (Synaptomys cooperi) which were also common in the area.