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Deer are native to much of the globe, with the exception of Australia
(where they are not native, but have been introduced) and most of Africa.
This is the most successful ungulate family presently in the Americas.
On the other hand, only a single subspecies of cervid (the Barbary
red deer, Cervus elaphus barbarus) is found on the bovid-dominated
African continent (but inhabits the Palearctic zoogeographical region).
Cervids are found in a wide variety of habitats, from the arctic tundra
to tropical forests. Only one deer species, the reindeer
(Rangifer tarandus), has been fully domesticated.
The Cervidae first appear as fossils in the early Miocene of Asia, where
they expanded into a wide variety of niches (and were thus able to dominate
over the bovids which arrived later). During
the Miocene, members of this family migrated to North America. After
expanding in the Nearctic region, deer crossed to South America during the
Pleistocene, when the Panama land bridge formed.
Antlers are the defining characteristic of this family: all but one species
(Hydropotes inermis) possess these cranial appendages, and they are
found in no other animal. Unlike the headgear of other Pecorans, antlers
are composed entirely of bone and often have elaborate branching patterns.
The antlers grow from an extension (the "pedicel") on the skull's frontal
bone, joining to the skull in a suture known as a burr. The sutures
holding the antlers to the deer's head decalcify on an annual basis (under
hormonal control), causing the antlers to fall off (usually in the late fall
or early winter in temperate species). After shedding, the antlers
soon begin to regrow. During the growth period, the expanding bone
is covered with a thin layer of fuzzy skin known as velvet, which helps protect
the growing tissue. Because the entire antler is alive, growth is not
limited to the base (as in horns) which results in branching patterns which
are often species-specific. Unlike the horns of bovids, the regular
shedding of antlers makes them a current marker of an animal's status: their
size and shape are in direct correlation to age and dominance. In the
vast majority of species, antlers are borne only by males - only in the reindeer,
Rangifer tarandus, do females regularly grow antlers.
Males of a few species possess enlarged, tusk-like upper canines
(Hydropotes, Muntiacus, Elaphodus). In other species
the upper canines are either vestigial or absent. The dental formula
is thus I 0/3, C 0-1/1, P 3/3, M 3/3 x 2 = 32-34. The molars are
selenodont, and usually brachyodont. There are usually two lacrimal
canals. Females usually have two pairs of mammae, and the young of
most species are spotted. There is no gall bladder. |
