Rut (mammalian reproduction)
The rut is the mating season of ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...

 animals such as deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...

, sheep, elk
The Elk is the large deer, also called Cervus canadensis or wapiti, of North America and eastern Asia.Elk may also refer to:Other antlered mammals:...

, moose
The moose or Eurasian elk is the largest extant species in the deer family. Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a dendritic configuration...

, caribou, ibex, goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...

s, pronghorn
The pronghorn is a species of artiodactyl mammal endemic to interior western and central North America. Though not an antelope, it is often known colloquially in North America as the prong buck, pronghorn antelope, or simply antelope, as it closely resembles the true antelopes of the Old World and...

 and Asian and African antelope
Antelope is a term referring to many even-toed ungulate species indigenous to various regions in Africa and Eurasia. Antelopes comprise a miscellaneous group within the family Bovidae, encompassing those old-world species that are neither cattle, sheep, buffalo, bison, nor goats...


During the rut (also known as the rutting period, and in sheep sometimes as tupping
Glossary of sheep husbandry
The raising of domestic sheep has occurred in nearly every inhabited part of the globe, and the variations in cultures and languages which have kept sheep has produced a vast lexicon of unique terminology used to describe sheep husbandry...

), males often rub their antler
Antlers are the usually large, branching bony appendages on the heads of most deer species.-Etymology:Antler originally meant the lowest tine, the "brow tine"...

s or horn
Horn (anatomy)
A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...

s on trees or shrubs, fight with each other, wallow in mud or dust, and herd estrus females together.

The rut in many species is triggered by a shortening of the length of daylight hours each day. The timing of the rut for different species depends on the length of their gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...

 (length of pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

), usually occurring so the young are born in the spring, shortly after new green growth has appeared (which provides food for the females, allowing them to provide milk for the young), and when the temperatures are warm enough that the young will not die of hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...


White-tailed deer

The rut for white-tailed deer
White-tailed Deer
The white-tailed deer , also known as the Virginia deer or simply as the whitetail, is a medium-sized deer native to the United States , Canada, Mexico, Central America, and South America as far south as Peru...

 (Odocoileus virginianus) usually lasts from 1–3 months in the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

 and may occur most of the year in tropical zones. The rut is the time when white-tailed deer, especially bucks, are more active and less cautious than usual. This makes them easier to hunt, as well as more susceptible to being hit by motor vehicles.

Some people believe that the white-tailed deer rut is also controlled by the lunar phase
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...

 and that the rut peaks seven days after the second full moon (the rutting moon) after the autumnal equinox on 21 September. However, study of white-tailed doe conception dates conducted in Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

 between 1980 and 1987 showed no correlation between peak breeding dates of white-tailed deer and any lunar phase.

A white-tail doe may be in estrus for up to 72 hours, and may come into estrus up to seven times if she does not mate. Cow elk may come into estrus up to four or more times if they do not mate.
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