Rut (mammalian reproduction)

Male impalas fighting during the breeding season called rutting

The rut is the mating season of ruminant animals such as deer, sheep, camel, goats, pronghorn and Asian and African antelope.

During the rut (also known as the rutting period and in domestic sheep management as tupping), males often rub their antlers or horns on trees or shrubs, fight with each other, wallow in mud or dust, self-anoint and herd estrus females together.

The rut in many species is triggered by shorter daylengths. For different species, the timing of the rut depends on the length of the gestation period (pregnancy), usually occurring so the young are born in the spring. This is shortly after new green growth has appeared thereby providing food for the females, allowing them to provide milk for the young, and when the temperatures are warm enough to reduce the risk of young becoming hypothermic.

Cervidae

White-tailed deer

The rut for white-tailed deer (Odocoileus virginianus) usually lasts 3 weeks in the Northern Hemisphere and may occur most of the year in tropical zones. The rut is the time when white-tail 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.^[1] The buck has one thing on his mind at this time of the year: to find as many does as he can. He will chase after many does for weeks, barely eating. The rut can take its toll on the bucks: they are usually quite worn out by the end of the breeding season.

Some people believe that the white-tailed deer rut is also controlled by the lunar phase and that the rut peaks seven days after the second full moon during October and November (the rutting moon), while elk begin rutting during the September equinox autumnal equinox on 21 September.

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 may come into estrus up to four or more times if they do not mate.

The rut can start as early as the end of September, and can last all the way through the winter months. Bucks usually begin to start this process when the velvet is falling off their antlers, and it can last all the way until they start to shed their antlers. The peak of the rut, however, is right in the middle. The average peak day for the white-tail rut in the U.S. is November 13.^[2] Around this period of time, the bucks and does are very active, with the rut in full swing. For a hunter sitting in a tree stand at this time of the year, it is not uncommon to see many deer pass through his specific area, due to other deer chasing others.

White-tailed bucks in late rut in the Great Smoky Mountains

There are many behaviors a buck will exhibit during the rut. During pre-rut, bucks will spar with each other. Sparring is low-intensity aggressive behavior, involving mostly pushing and shoving. Bucks of different sizes will do this to each other. After pre-rut is finished, a buck will rub his antlers on a tree (thus making a “rub”), and make scrapes on the ground with his hooves: both of these are ways a buck will mark his territory and proclaim his dominance for other bucks to see. These activities are usually done at night.^[3]

The most prominent behavior of all during the heat of the rut is fighting, where bucks show their true dominance to others. In fighting, bucks usually battle against similar sized deer, and small bucks do not normally challenge mature large ones: more often than not, smaller bucks fear the more mature bucks and leave or avoid the dominant deer’s territory. The fights can go on and on, with the winner getting the group of does. Some fights go on until death, and if not, it is not unusual to see one of them get injured.

The energy expenditure of chasing and fighting during the breeding season can result in a buck losing an immense amount of weight, with some research documenting losses of as much as 20% of body weight. On average, a buck before breeding season can weigh up to 180 pounds (82 kg). After he has gone through the stages of rut, he can lose about 50 pounds (23 kg) of weight, which is quite large, especially for only a few months of time. In the post-rut, a buck will need to replenish his body and catch up on the weight and energy he has lost.

Sources have stated that after the rut, a buck will go to a bedding spot and will remain “motionless” for a large amount of time, even to the extent of about two days, as he is thoroughly exhausted. After he has rested, he will get up and start to feed extensively, trying to catch up on all the nutrients his body requires. Croplands have much high carbohydrate grain in them, and a buck can be found here often, eating and getting nutrients. When the climate is extremely cold, a buck will sometimes resort to swamps and bogs, because of the warmer temperatures these areas hold.

Elk

The elk rut takes place between the middle of August and the middle of October, depending on the climate in which they live. The elk rut occurs around the same time of year throughout the United States. For example the peak rut in Idaho occurs between September 20 and 25, while the peak rut in New Mexico occurs around September 14.^[4] The rut tends to last somewhere between 20 and 45 days.^[5] This varies on latitude, for in southern areas spring arrives earlier and fall arrives later giving elk a longer calving season, therefore the rut lasts longer.^[4] During the rut elk frequently use areas around fresh water, and tend to bed in heavy timber five to six hours per day.^[6]:579 A cow elk will remain in estrus for 12 to 15 hours, if they are not bred during this time frame they will normally have another estrus cycle 18 to 28 days later.^[4]

Elk use several different vocalizations during the rut. Some are made only by a certain sex or age class, and each is used for a different reason. The first of which being the cohesion call which is made by both sexes of elk, and is used to locate one another.^[7]:225 An alarm squeal is made by both sexes of elk when they are on alert, during the rut these are used frequently by young bulls (male elks) being run off by the herd bull.^[7]:228 Satellite bulls frequently spar with one another during the rut, and in turn make sparring squeaks.^[7]:228 A bugle is a vocalization made exclusively by bulls. A bugle can be directed toward other bulls or toward cows. A bull will direct his bugle toward his cows while gathering them or while chasing an estrus cow. A herd bull will direct his bugle toward another bull to express his dominance over the herd, while a satellite bull may use his bugle to challenge the herd bull.^[7]:229 Yelping also known as “grunting” is usually only made by herd bulls when they are excited. They are made more often while interacting with cows than with other bulls. “Yelping commonly was accompanied by contractions of the penile region with simultaneous emission of short spurts of urine.”^[7]:230

Phases

The rut has six phases: the pre-rut, the first breeding phase, the first rest phase, the second breeding phase, the second rest phase, and the third breeding phase.^[4]

• The pre-rut takes place from mid-August through the beginning of September. During the pre-rut bulls begin bugling and gathering their herds. Bulls will bugle to attract cows as well as to express dominance over other bulls. A “herd” bull is the dominant bull in a herd. Younger, smaller bulls are known as satellite bulls, as they tend to cling to the edges of a herd trying to pick up any cows willing to leave the herd. Larger satellite bulls will challenge the herd bull to try and take control of the herd. These challenges include a good deal of bugling as well as fighting.^[4]
• The first breeding phase of the rut takes place between the beginning and the middle of September. This is when the three year and older cows come into estrus. During this time herd bulls bugle to keep their cows close by, they also answer the bugles of satellite bulls to let them know they are still dominant. A herd bull will also bugle while approaching a cow in estrus so the cows become familiar with his bugles.^[4]
• The first rest phase of the rut occurs between the middle and the end of September. At this time the older cows are predominantly out of estrus and the younger cows have not yet come into estrus. During the rest period satellite bulls will try to join the herd while the herd bull is resting.
• The second breeding phase of the rut takes place three to four weeks after the first breeding phase. This is due to younger cows coming into estrus, as well as older cows that were not breed on their first estrus cycle coming back into estrus. Herd bulls are less aggressive towards satellite bulls at this phase in the rut due to exhaustion.^[4] The second phase of the rut may have the most bugling activity due to the combination of the testosterone levels of the younger bulls rising, and the herd bull still trying to maintain control of the herd.
• The second rest phase of the rut occurs around the middle of October. By this time the original herd bull usually does not have control of the herd, due to a great decline in physical condition. Terry Bowyer states, “Elk were observed feeding in the following percentages of observations: master bulls 24%; bachelor bulls 53%; yearling males 62%; cows 64%; and calves 62%” (Bowyer uses the terms “master bulls” and “bachelor bulls” which have the same meaning as “herd bulls” and “satellite bulls”).^[6]:577 Herd bulls do not have time to feed during the rut due to constantly fighting other bulls as well as chasing and breeding cows.^[4]
• Occasionally a third breeding phase will occur. This will usually take place around the end of October or early November. This is a result of yearling cows coming into estrus for the first time or two-year-old cows coming into a second estrus cycle. Since most of the herd bulls have left the herd by this time of year, the breeding is usually done by the younger satellite bulls. After this phase the rut is over, most bulls will leave the cows and form bachelor herds to spend the winter with; however young bulls will usually remain with the cows throughout the winter.^[4]

Other deer species

Other mammals

• Warthog#Reproduction
• Spanish ibex#Mating
• Muskox#Social behavior and reproduction
• Argali#Reproduction
• Camel#Biology

See also

• Even-toed ungulate#Reproduction and life expectancy
• Lek

Notes

References

• Ozoga, John J.; Verme, Louis J. (October 1975). "Activity Patterns of White-Tailed Deer during Estrus". Journal of Wildlife Management. Wiley. 39 (4): 679–83. doi:10.2307/3800227. JSTOR 3800227. 
• Weiss, John. “The Post-Rut Lull.” Outdoor Life (December 1998): 28. Academic OneFile. Web. 11 Oct. 2012.

Further reading

• Strategies for Whitetails. Krause Publications. 16 May 2006. ISBN 0-89689-331-6. 
• Valerius Geist (January 1998). Deer of the World: Their Evolution, Behaviour, and Ecology. Stackpole Books. ISBN 978-0-8117-0496-0. 
• Jim Heffelfinger (8 September 2006). Deer of the Southwest: A Complete Guide to the Natural History, Biology, and Management of Southwestern Mule Deer and White. Texas A&M University Press. ISBN 978-1-60344-533-7. 
• David G. Hewitt (24 June 2011). Biology and Management of White-tailed Deer. CRC Press. ISBN 978-1-4822-9598-6.