Have you seen a male mule deer acting strangely this fall? Perhaps in a place you wouldn't normally see one during the day? Maybe a little distracted? Chances are, you saw a buck in the throes of the seasonal rut.
The timing of the rut is based on the gestation period of females, which for mule deer is roughly 200 days. Females generally go into estrus for a two- to three-week period in mid-November, giving birth the following June. Fawns born too early are susceptible to late spring weather, while those born too late will have a shortened time to grow and prepare for the following winter. During the rut, male mule deer compete for the right to mate, exhibit riskier behavior and subsequently, are easier to observe. The improved opportunity to land a big buck is one reason why hunting season generally coincides with the rut. This year, mule deer will face a reduced threat from the rifle, as 79,800 licenses were issued this season, down 6 percent from 2011.
Part of the reason for this is that mule deer have been steadily declining in numbers across their range. Found west of the 100th meridian, which splits the states of Nebraska and Kansas, mule deer are found as far north as the Yukon Territory and south to the province of Zacatecas in central Mexico.
Historical records testify to the original abundance of mule deer encountered by early settlers. Early market hunter Frank Mayer wrote about his experience hunting at the confluence of the Blue River and the Colorado just south of modern day Kremmling in 1878: "As the migration is now well begun, I encounter elk and deer at all hours of the day. They are crossing the river junction in such numbers that shooting them requires no skill." Later in his journal, Mayer records that he shot 89 mule deer in 78 days and finally quit when he became "tired of killing."
As a result of this large-scale harvesting, the Colorado Territory established its first wildlife protection agency in 1879, which immediately began enforcing season and bag limits for many species. Despite the regulations, according to a study conducted by Colorado State University in conjunction with the Colorado Division of Wildlife, mule deer populations didn't fully rebound until after the dust bowl era of the early to mid 1930s. While exact numbers were not collected until the 1970s, wildlife professionals generally agree that herds reached modern highs in the 1940s, with populations between two or three times as large as the current 2012 post-hunt estimate of 420,000.
Why are mule deer populations declining? The answer is complex.
"There's no single cause," Colorado Parks and Wildlife big game manager Andy Holland recently told The Denver Post. "Between severe winters, increased development, habitat decline and migration corridor fragmentation, most Western states are seeing declines in mule deer populations."
Not mentioned by Holland are other associated factors including predation from hunters and coyotes, competition from elk and poor quality of forage due to the introduction of invasive species. Often the most contentious variable is that of coyotes. While some organizations and states have taken steps to limit coyote populations, state officials and biologists in Colorado maintain that there is no statistical correlation between coyote predation and reduced numbers of mule deer.
An iconic figure of the West, the mule or black-tailed deer (Odocoileus hemionus) is an impressive figure. Mule deer are shorter and bulkier than white-tailed deer (Odocoileus virginianus) and can grow to a maximum size of 51⁄2 feet long, 31⁄2 feet tall and weigh up to 450 pounds. Because of their smaller digestive system, mule deer are unable to graze aggressively like elk and larger ruminants and instead browse and eat selectively, relying on choice trees, shrubs and grasses. In addition, mule deer are specialists that thrive in unspoiled areas, as opposed to their white-tailed cousins which readily adapt to suburban environments.
How can we best preserve and protect healthy mule deer herds in our valley? Go hunting! Current research indicates that legally harvested animals do not negatively impact the strength of mule deer herds, while the money raised by the Department of Parks and Wildlife helps to fund ongoing research and good management practices. In addition, hunting is a good way to gain insight into the natural habits of deer, build a lasting connection to one of the region's most iconic species and lay the groundwork for long-term preservation.
John Ceballos is a natural science educator at Walking Mountains Science Center. John enjoys bushwhacking in search of wildlife and went hunting for the first time ever in 2012.