Mammals
Deer
Cervidae · also called deer, cervids
A deer builds a weapon on its head every year and then throws it away. The antlers a stag carries into the autumn rut are grown from bare bone in about a hundred days — the fastest ordinary bone growth known in any animal — stripped of their velvet, fought with, and dropped a few months later so the whole extravagant process can start over.
Overview
Deer are the family Cervidae, around 50 species, native to the Americas, Europe, Asia, and northwest Africa. All are hoofed herbivores that chew the cud, and in almost all of them the males grow antlers. They range from the 10 kg pudu to the moose at over 700 kg, and the family includes elk, red deer, reindeer, fallow deer, sika, roe deer, and the tropical sambar and chital.
Antlers
Antlers are pure bone, grown fresh each year from bases on the skull, covered while growing in a living skin called velvet, then bared, used through the rut, and shed. Only in reindeer do females grow them too. Antler size honestly signals a male’s condition, since a male in poor shape cannot afford a big rack.
Older weapons
The tufted deer, muntjacs, and water deer keep long sabre-like upper canines instead of or alongside antlers — a trace of the tusked deer that came before antlers evolved.
Sprinters and hiders
Deer pair light bodies and long legs for bounding escape, sometimes with a stiff-legged bounce called stotting, with near-odourless newborns that lie hidden in cover for weeks while the mother feeds nearby.
Winners and losers near people
White-tailed, roe, and red deer have boomed where large predators were removed and farmland and young forest spread, reaching densities that stop woodland regenerating and cause many vehicle collisions. Meanwhile many tropical and island deer are threatened, and Schomburgk’s deer of Thailand was driven extinct last century.
Status
Deer as a family are Not Evaluated. Temperate species are abundant and locally overpopulated; several tropical and island species, including the South Andean huemul and the Bawean and Calamian deer, are endangered.
Deer: common questions
What is the difference between antlers and horns?
They are completely different structures. Antlers, found only in the deer family, are made entirely of bone, grow and are shed every year, are usually branched, and in almost all species are grown only by males. While growing they are covered in a furred skin called velvet that carries blood vessels and nerves, which the animal rubs off once the bone hardens. Horns, found in cattle, sheep, goats, antelope, and their relatives, have a bony core covered by a permanent sheath of keratin, the same material as fingernails, are never branched, are usually grown by both sexes, and are kept for life, growing a little each year. Rhinoceros horn is different again, being made only of compacted keratin with no bone at all.
Why do deer grow antlers just to throw them away?
Because the yearly cycle lets a male carry the largest possible weapon and status symbol exactly when it matters, during the autumn rut, without paying to maintain and heal it for the rest of the year. Antler size signals a male's condition to rivals and to females, and males with bigger racks win more fights and mate more. Growing that much bone each year is costly and draws heavily on body and skeletal reserves, so a male in poor condition grows a smaller rack, which honestly advertises his state. After the rut the antlers are dead bone and no longer useful, so shedding them saves weight and lets any damage be discarded and replaced with a clean set next year.
Are elk, moose, caribou, and reindeer all deer?
Yes, all of them are members of the deer family, Cervidae. Moose, called elk in Europe, are the largest living deer. The animal North Americans call elk is a different species, the wapiti, also large and a close relative of the European red deer. Caribou and reindeer are the same species, Rangifer tarandus, with caribou the wild North American name and reindeer the Eurasian and domesticated one. The family also includes fallow deer, sika, roe deer, white-tailed and mule deer, the tropical sambar and chital, the tiny pudu and muntjac, and the marsh and swamp deer, spanning a size range from about 10 kg to over 700 kg.
Why have deer become so common in some places?
A combination of changes has favoured them. The large predators that once kept deer numbers down, wolves, cougars, bears, and lynx, were hunted out of much of Europe and eastern North America. At the same time, clearing mature forest for farms and then allowing patches to regrow created exactly the mix of open feeding areas and dense young cover that species like white-tailed deer and roe deer thrive in. Hunting has declined in many suburban areas where firearms cannot be used. Mild winters help more fawns survive. The result is deer densities far above historic levels in places, heavy browsing that stops woodland regenerating, more deer-vehicle collisions, and higher tick-borne disease.