Red deer are easy to identify due to their mostly uniform color: dark reddy-brown in summer, turning to grayish-brown in winter. During both seasons the underbelly is paler. The females have a face and throat that are paler than those of the males, particularly in summer. Adult red deer are hardly ever seen with spots, or if so, there are not many of them. The distinguishing feature for stags is their antlers, which in mature adults are long and branched. The longer branches usually sweep backward and have a number of much shorter ones in front.
Red deer inhabit most of Europe, Asia Minor, the Caucasus Mountains region, Iran, areas of western Asia, as well as central Asia. There are also the only species of deer living in Africa, namely, the Atlas Mountains area in northwestern Africa between Morocco and Tunisia. They have also been introduced to Australia, New Zealand, the United States, Canada, Uruguay, Peru, Chile, and Argentina, amongst others. Red deer like open woodlands and they avoid dense unbroken forests and can be seen in coniferous swamps, aspen-hardwood forests, clear cuts, and coniferous-hardwood forests.
These deer are social animals, living in summer herds with up to 400 individuals. The herds are matriarchal, being dominated by a single female. Seasonal migrations occur, with deer moving to higher elevations for the summer, and to lower elevations over winter. In spring, the sexes separate after the mating season, females leaving to give birth, bulls forming separate summer herds. Bulls during the mating season are territorial and otherwise are not aggressive towards other deer. Red deer browse early in the morning and late evening. During the day and late at night they are inactive, spending most of this time chewing their cud.
Red deer are browsers, eating grasses, forbs, and sedges in summer, and, in winter, woody growth (cedar, wintergreen, sumac, eastern hemlock, jack pine, staghorn, red maple, and basswood). Deer particularly like dandelions, aster, hawkweed, clover, violets, and sometimes mushroom. Deer are ruminants, regurgitating their food and chewing it up again (i.e. chewing their cud) to aid digestion.
Red deer are polygynous, one male mating with multiple females. In late September or early October, the males lose their antler velvet and start to compete for females. Dominant males can maintain larger harems and restrict access to their females. Harems are seasonal and usually consist of 1 bull with 6 females and their yearling calves. These deer reach sexual maturity at 16 months, although males usually wait until a few years have passed and they can compete with the more mature males. Gestation usually lasts 240 to 262 days, and a single offspring is born. Following birth, a cow and a calf live alone for a few weeks. After 16 days a calf can join the herd, with weaning completed within 60 days. The mothers nurse and protect their offspring for the first year of life. Males do not help with the care of their young.
Predators include mountain lions, bears, and gray wolves. Calves may be eaten by bobcats and coyotes. Limited hunting for sport is generally permitted and in some countries, they are farmed for meat.
The worldwide population number of the Red deer is unknown, but particular populations in Europe have been estimated, with a total of approximately 1.7 million individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are increasing.
Red deer have an important impact on the plant communities where they live, due to their browsing. They serve as important prey during certain times of the year for some large predators, including brown bears.