Cervus is a genus of deer that primarily are native to Eurasia, although one species occurs in northern Africa and another in North America. In addition to the species presently placed in this genus, it has included a whole range of other species now commonly placed in other genera, but some of these should perhaps be returned to Cervus. Additionally, the species-level taxonomy is in a state of flux.
Taxonomy
Genus
Until the 1970s, Cervus also included the members of the genera Axis, Dama, Elaphurus and Hyelaphus, and until the late 1980s, it included members of Przewalskium, Rucervus and Rusa. With the exception of the chital, barasinga, Schomburgk's deer, and members of the genus Dama, genetic evidence suggests all should be returned to Cervus.
Species
In the third edition of Mammal Species of the World from 2005, only the red deer and sika deer were recognized as species in the genus Cervus. Genetic and morphological evidence suggest more species should be recognized. For example, the subspeciesC. e. canadensis is considered by some to be a separate species.
Within the red deer species group, some sources have recommended the elk or wapiti and Central Asian red deer should be treated as species. If the Central Asian red deer is recognized as a species, it includes the Yarkand deer and Bactrian deer, but it could possibly also include the Kashmir stag, which has not been sampled in recent studies. If it is included in the Central Asian red deer, the scientific name of that species is C. hanglu. If it is not included, the scientific name of that species is C. yarkandensis, and the Kashmir stag may represent a separate monotypic species. Others members of the red deer group, which may represent separate species, are C. corsicanus, C. wallichi and C. xanthopygus. If so, C. corsicanus includes the subspecies C. c. barbarus, and is restricted to Maghreb in North Africa, Corsica and Sardinia. C. wallichi would probably include the subspecies C. w. kansuensis and C. w. macneilli, and would be found from Tibet to central China. C. xanthopygus would probably include the subspecies C. x. alashanicus, and would be found from the Russian Far East to northeastern China. This would restrict the "true" red deer to Europe, Anatolia, the Caucasus and northwestern Iran, and the elk/wapiti to North America and the Asian regions of the Tian Shan, Altai, and Great Khingan. Alternatively, the barbarus group species are subspecies of the "true" red deer, while the C. wallichii and C. xanthopygus groups are subspecies of the elk/wapiti.
The sika deer should be split into four species based on genetics, morphology and voice, although this may be premature based on the presently available evidence. If split, the potential species are C. yesoensis from northern and central Japan, C. nippon of southern Japan, C. hortulorum of mainland Asia, and C. taiouanus of Taiwan.
Mating system
Members of the genus Cervus have polygynous mating systems within harems. These harems consist of several males, numerous females and their young offspring 1–3 years in age Members of this genus have a yearly breeding season where they display sensory exploitation, intrasexual competition, and weaponry. Females will fight for optimal mating opportunities and sexually selection for males with larger antler size and/or greater roar quality. The degree of polygyny and female aggregation is dependent on the level of food distribution. Females aggregating in areas with more food leading to larger harems Female distribution influences the level of polygyny.
Female-female competition has been observed within harems in the red deer species prior to and during the mating season. Aggression is displayed through nose threats, kicking, and displacements. Elevated aggression has only been observed during the breeding season. Competition can be for access to mates or reproductive resources such as food, or nesting areas. Female-female aggression in ungulates is often overlooked because it is not as extravagant as male antler combat. Female conflicts occur so the winner has first access to the harem male at the start of the mating season before he is exhausted or low on sperm storage.
Secondary sexual traits
While an emphasis in observations of sexual selection is placed on combat using antlers, males with higher roaring rates are also being selected for. During the breeding season males will make calls to attract mates and compete with other males. Like antler size, mating call quality is an indicator of mate potential. Red deer can distinguish the calls of the males in their harem, others and their offspring.
Indirect benefits
Females select for males with larger antlers which indirectly benefits them. Large antler size in males is a sign of health and strength. The visual display is a reliable indicator of mate quality, providing indirect benefits. The females are not directly affected by these characteristics, but they will produce more viable and fit offspring. Males with large antlers mate and sire more offspring than smaller, younger males. Large antler size is correlated with overall health, fitness and an increase in sperm production and quality.
