Date: 04/06/05
Contact: Jill Olson
Phone: (775) 688-1998
Mule Deer in Nevada – Habitat and Biology Part 1
By: Jill Olson from a report by Tony Wasley
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As the big game hunting application period has arrived in Nevada, hunters are thinking about the type of species and the areas for which they will apply for 2005 big game tags. For many, mule deer are the first choice. Understanding the basics of mule deer behavior and habitats can not only help hunters during the actual hunt, but it can also help them understand some of the factors that biologists consider when recommending quotas and season dates. This article is the first in a series discussing mule deer populations in Nevada. Mule deer population is not a cut and dry issue based on only one factor; many factors combine and influence each other to effect ultimate population. A basic understanding of mule deer biology and habitat is the foundation of all these factors. Breeding season, or the rut, for mule deer occurs in November. Single or twin fawns are born between May and August after a seven month gestation period. Females are most productive when they are two and a half years of age and older. Nutritional quality is very important in the success of mule deer production. Higher quality forage is needed to build the fat stores needed for healthy ovulation, conception, and pregnancy in does. Because mule deer do not stay in one area all year long, habitat quality throughout their migration corridors is very important. Mule deer move between various zones from the forest edges at higher elevations to the desert floor, depending on the season. Generally, they summer at higher elevations and winter at lower elevations, following the snow line. Mule deer occupy almost all types of habitat within their range, yet they seem to prefer arid, open areas and rocky hillsides. Areas with bitterbrush and sagebrush provide common habitat. Mule deer are most active in mornings and evenings, allowing them to conserve water and keep body temperatures down in desert environments. Seasonal movements from higher elevations to lower winter ranges are affected by food supply and ability to move through migratory corridors due to temperature and rain or snow conditions. Mule deer are herbivores and browsers. What they eat depends on their habitat, but common food includes forbs (broad-leaved herbaceous plants) and woody browse like sagebrush and bitterbrush. Their four-chambered stomachs contain special which allow them to digest this very fibrous natural vegetation. Without these microbes, they are unable to break down the food to create the energy they need to survive. Being a picky eater is not only a human trait. Mule deer have definite preferences for certain types of plants, and also for the specific parts of the plant. This preference may change depending on the time of year. Mule deer tend to like the tenderest parts of plants like new shoots or “leaders” on the vegetation. These leaders pack the biggest punch in terms of quality and amount of nutrition, plus they are the easiest to bite, the most flavorful, and easiest part of the browse to digest. Because mule deer are so selective, that means they have very specific habitat requirements. Our picky mule deer that prefer “leaders” have the best chance of finding these delicacies during the ideal conditions created by good winter snow packs, and consistent spring and summer rains. Unfortunately, in the driest state in the nation and seven years into drought, these ideal conditions are not a reality much of the time. Drought is especially difficult on mule deer and their habitats. Both winter and summer/spring precipitation are important in maintaining quality habitats. The amount of precipitation received during these times effects the growth and abundance of food available for mule deer. Additionally, when plants do not receive enough water in the summer months they begin to go through a sort of hardening process to help from drying out. As the plants toughen, it makes them even harder to digest by mule deer, forcing them to use even more energy just trying to pull out the nutrients of this tough browse. The quality of mule deer habitat is very important. Research has shown over and over that deer on high quality ranges have better body condition which results in higher rates of ovulation, conception, and pregnancy than deer on poor ranges. Poor body condition means that a deer may not have enough energy or fat stores to meet the basic energy demands of life (like maintaining a constant body temperature, rutting, breeding, birthing, feeding offspring, avoiding predators or fighting off disease). Additionally, quality habitat provides cover for mule deer: places to escape from energy sucking wind, heat and weather, as well as predators. Quality habitat is key not only to mule deer survival on an individual basis, but also to the success of mule deer reproduction and survival rates that ultimately boost populations. Besides drought, pinyon-juniper encroachment, old-aged and lower-quality vegetation, fire, invasive weeds, human factors (houses, roads, mines, grazing) all are factors that can negatively impact mule deer habitat. We will discuss these factors in more detail in Part 2 of this series. This information is taken from “ Nevada’s Mule Deer – Population Dynamics: Issues & Influences,” available at Nevada Department of Wildlife offices for $10.00. The Nevada Department of Wildlife is the state agency responsible for the restoration and management of fish and wildlife resources, and the promotion of boating safety on Nevada’s waters. Wildlife offices are located in Las Vegas, Henderson, Ely, Winnemucca, Fallon, Elko, and Reno. For more information, contact the agency web site at www.ndow.org.
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