I once stalked a solitary antelope by creeping flat on the ground through a prairie-dog “town.” As I drew near the first burrows, the “dogs” all rushed to their mounds, sitting there and barking at the queer and unknown animal thus invading their precincts. The strange sight excited as much curiosity among them as alarm. As I approached one mound after another the owners would become almost hysterical in their excitement and would sit first on all fours and then stand up at full height on their hind feet, the tail all the time vibrating as though worked by some mechanism, while the barking continued at the intruder as rapidly and explosively as possible. When I came within six or eight feet the “dog” would dive down his hole, sputtering barks from the depths as he went, but often would pop up again to take another look before finally disappearing. In this way I passed ten or a dozen mounds while the dozens of “dogs” off my line of progress worked themselves into a frenzy of curiosity and protest. When the stalk was finished I passed back through the “town” and my upright figure was promptly recognized by the habitants as that of an enemy and every one disappeared before I was within fifty yards of the first mound. The common note of the black-tailed prairie-dogs is a squeaking “bark,” much like that produced by squeezing a toy dog; in addition, there is a rapid chattering note, often given as the “dogs” vanish down the hole. The white-tailed species have a shriller, more chirping note. In both species the odd vibrating motion of the tail, held stiffly close to the back, is characteristic. Prairie-dogs hibernate in severe weather, those living in high, snow-covered mountains or in the far north sometimes sleeping through five or six months. In many places their hibernation is irregular, and near the southern border of their range is limited to a few inclement days now and then. In Wyoming they come out the last of March or early in April, sometimes when there is a foot or two of snow on the ground and the temperature ranges far below zero. Under such conditions they run about over the snow during the middle of the day, feeding on projecting tips of vegetation or digging to the ground. Beginning near the southern border of their range and proceeding north, the single litter of the season, containing from four to six young, are born in March, April, or May, and a month later, when scarcely larger than chipmunks, may be seen playing about the entrance mound. When danger appears the mother sends the young helter-skelter for the refuge of the burrow, and should any be slow about going in she rushes at them, driving them to cover with shrill barks of alarm. When about half-grown the young scatter and prepare burrows of their own. Sometimes as many as six to nine of these animals may be found in a single burrow, in which, no doubt, they have taken refuge, or it may be a reunion of the season’s family.