During the mating season of temperate species, males use one of three strategies to obtain access to receptive females. They may defend a territory that overlaps the ranges of females, as does the muntjac. They may defend a single doe against all suitors, as does the white-tailed deer. Or they may attempt to assemble and hold a harem of females, as does the red deer (Cervus elaphus). The males and females of this gregarious species spend most of the year in single-sex herds, which generally have particular ranges. Come September, the females gather in rutting areas, and are soon joined by the males, which compete for the females through displays of roaring, spraying urine, and fighting.
Fighting begins when the challenger appears, and he and the holder of the harem roar at each other. After several minutes of vocalizing, they walk parallel to each other, tense and alert, until one of them turns toward the other and lowers his antlers. They lock antlers and begin shoving each other. When one succeeds in pushing the other backwards, the loser runs off.
The fights are dangerous. Almost a quarter of the males in a Scottish study were injured during the rut, 6% permanently. A male between ages of seven to 10 has the best chance of winning such an encounter, which a harem holder must face about five times during the mating season. There is another danger besides injury; young males often lurk at the fringes of a harem, waiting until the harem holder is distracted and then spiriting away a female or two. The apparent benefits of holding a harem are deceiving; although there may be as many as 20 females in the harem, the male will father only about four or five calves.
Females of tropical species of deer come into estrus several times a year. Gestation lasts from 176 days in the Chinese water deer to 294 days in the roe deer. The female deer delivers from one to six young (six in Hydropotes), but one or two is the norm. The young of most deer are born spotted.
The males of the Cervinae (such as the red deer) are called stags, the females, hinds, and the young, calves. Among the Odocoileinae, the male deer are called bucks, the females does, and the young fawns. Exceptions are Alces (moose) and Rangifer (caribou), in which the males are bulls, the females, cows, and the young, calves.
Besides the moose, other North American species include the white-tailed deer (Odocoileus virginianus) found from southern Canada, throughout most of the United States, Mexico, and down to Bolivia and northeastern Brazil. The white-tailed deer may be the most abundant species of wild large mammal, with a population of about 60 million individuals. The mule deer (O. hemionus), named for its large ears, ranges from the southern Yukon and Manitoba to northern Mexico. The tiny Key deer (O. v. clavium) is an endangered sub-species of the white-tailed deer; only about 250 remain in the western Florida Keys.
F. C. Nicholson