Why Are There So Many White-Tailed Deer?

A Buck made of many deer in the forest with the title, "Why are there so many white-tailed deer?"

White-Tailed Deer Reproductive Cycle

Life cycle of deer. Fawn to yearling to buck and doe.

The Basics

White-tailed deer, Odocoileus virginianus, have an individual range of about one square mile. However,white-tailed deer as a species; are found over much of the U.S., Canada and all the way down through Central America, even making it down to northern South America.

 During winter months, male white-tailed deer can, at a minimum, travel .31 miles further than their normal range for reproduction purposes, food availability, and population density.

Range Map of White-Tailed Deer Subspecies (North America)
Range Map of White-Tailed Deer Subspecies: Biology and management of white-tailed deer / edited by David G. Hewitt. Boca Raton : Taylor & Francis, 2011. 674 p. (ISBN:9781439806517) (OCLC:731192045)
Range Map of White-Tailed Deer Subspecies (Central and South America)
Range Map of White-Tailed Deer Subspecies: Biology and management of white-tailed deer / edited by David G. Hewitt. Boca Raton : Taylor & Francis, 2011. 674 p. (ISBN:9781439806517) (OCLC:731192045)

White-tailed deer Inhabit anywhere from cities, to grasslands, to tropical rainforests. As the year progresses these inhabited areas can adjust. This can be caused by changes in food availability and breeding season.

It is possible for white-tailed deer in the wild to live up to 20 years and even 30 years in captivity. However this is usually not the case due to predation and hunting of older animals that are not as able as they once were. Because of this, most white-tailed deer live only about 10 years.

Bucks

White-tailed buck at sun set

Male white-tailed deer, known as bucks, will leave their mother after about one year.  They will start to grow antlers at two years. In the fall, males rut, which means that they are becoming hormonal to start reproduction. Bucks will stay with the same herd and attempt to assert dominance but will sometimes leave the herd to challenge other males.

As the length of daylight decreases, the bucks will get melatonin released in their brain to trigger their mating characteristics. These characteristics include the hardening of their antlers and increases in testosterone levels. The testosterone increase results in their sperm being able to mature and having other bodily changes, such as a swollen neck.

Bucks make a social hierarchy based on dominance. They will spar with each other during this time of year. Antlers will be lost soon after and a new pair will grow in the next season. White-tailed bucks will also scrape their antlers against trees to mark that they are ready for mating and also will get more aggressive about territory. Think of it like a calling card. The marking shows females their health, age, and dominance in the area. Females are looking for the best genes to make sure their offspring have the best chance at survival. 

Does

white-tailed doe portrait

Female white-tailed deer, known as does, are ready to give birth to fawns after about two years. They typically stay with the same herd for their entire life. As the daylight begins decreasing, does go into heat. This is known as “short day” breeders. Does can go into heat multiple times during the reproductive season and one occurrence lasts about 28 days. The female white-tailed deer will visit the trees scraped by males which signals their body to become ready for mating. They will release pheromones from glands on their hind legs to attract the bucks that left their markings.

After mating, white-tailed bucks will stay with the female for a couple of days to make sure no other males are able to mate with her. This is done to increase the likelihood of passing along their genes.

White-tailed deer on average have litters of 1 to 2 fawns. Number of offspring increases with age of a doe and has been seen to be as many as four. Available nutrition is another key factor in reproductive rates. Breeding season can be as early as August but is typically in November It can go as late as December and into January as well.

Fawns

Doe and fawn in the woods

White-tailed does carry the developing fawn for six months and give birth in May and June. This reproductive timeline is specific so that when the fawns are born, they have a better chance at survival due to increased food availability from lush plants. The mother will move away from the herd to give birth. The white tailed doe will look for an area of dense vegetation to hide newborns from predators.

The young deer, also known as fawns, are able to walk as soon as they are born. They have white spots to help them hide from predators. These spots resemble light filtering through the woods and are great camouflage. They then lose spots after about a year. They will feed off of the mother’s milk and even start supplementing their food with plants after only a few days. About a week after birth the fawn will join the herd. After about six weeks the fawns will be completely off their mother’s milk and be eating on their own.

Yearlings

Yearling eating from a garden

Growing out of being a fawn, the young deer are now known as yearlings. Female yearlings will stay with their mother for two years as opposed to males which will only spend a year. Spots are lost after the first winter. Fawns will be driven off by the mother just before the next time they give birth.

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