The Link Between Biology and Better Hunting

By Trail Kreitzer, Professional Hunt Advisor, July 2016

For the most part, we are through the dog days of summer and archery seasons are just getting underway. It’s an exciting time of year full of anticipation and promise. Hopefully this year all of our practice, preparation, and scouting will result in memories that will last a lifetime. I had some luck in the state draws, and I’ve got a few permits in my pocket for antelope, deer, and elk that span various weapon types, seasons, and three states, everything from early season archery antelope and muzzleloader deer to late season rifle deer and elk.

The primary reasons I hunt are to experience the outdoors and adventure, explore, and challenge myself. However, every time I put on my camo and shoulder my pack, my intent is to fill my permit. For any hunter to harvest regularly with different weapons and seasons, they have to have the knowledge, tools, and skills to get the job done, and knowledge is the foundation of those three. While working for the Utah Division of Wildlife Resources as a Habitat Biologist, and perhaps even more so now, I commonly receive a few of the same questions.

Where should I hunt, and where can I find animals? Where are the big bucks and bulls likely to be? What does the feed/forage look like this year, and what does that mean for antler growth? In this article, I will take an in-depth look at the life history of elk and mule deer and the habitat types they select throughout the year. I’ll also expound on types of forage they consume and what that might mean for antler and population growth. Hopefully this will provide you with some useful information that will aid you in your scouting and hunting efforts.

Elk and deer have a ruminant digestive system that utilizes a four-chambered stomach to extract nutrients from forage. Tough plant fiber is initially swallowed and stored in a chamber where bacteria and protozoa begin breaking down the plant material. They later regurgitate their food to chew it thoroughly, further breaking it down. Food is then swallowed once again, passing through three other chambers where it is further processed, water is absorbed, and nutrients are absorbed through the intestines. Generally, the smaller the ungulate, the more specialized and selective the animal has to be in making food choices to meet its dietary needs. Elk are large animals with more rumen and fiber digesting capacity than smaller species, like mule deer, and can get away with consuming larger amounts of lower quality forage. Elk are primarily grazers, where mule deer are more selective and primarily browsers.

During the spring and summer months, bucks and bulls will spend their time in solitude or small bachelor groups. These months are critical to males that are rapidly growing antlers and preparing for the rut and to females that require more nutrition during gestation and lactation. Elk calves are born in late May or June after a gestation period of approximately eight months. The gestation period for mule deer is seven months. Mule deer fawns are typically born within a similar timeframe, but there is some variation, especially the farther south you go. The timing of reproduction and birth of fawns/calves is thought to be correlated with peak development and nutritional content of the vegetation. Does will produce one fawn their first breeding year and may produce twins regularly in years after. Cow elk typically have one calf, but twins are not uncommon.

Spring foraging is focused in areas where palatable new green growth is readily available, typically at higher elevations where moisture and climate regimes are more favorable. Since new growth is higher in protein and energy than decadent vegetation, deer and elk seek out new forbs, green grasses, sedges, and new growth on browse species. Forbs are the best diet component that allows both species to address their nutritional needs. Forbs are broad-leafed flowering plants (non-grasses), such as dandelions and clovers. They are highly palatable and packed with protein and nutrients. Green up typically occurs first on south and west-facing slopes, and deer and elk will move into higher elevations as snow melts and the newest, most nutrient-rich plants begin to grow. Forest ecosystems with a mosaic of feeding and bedding cover are preferred during summer months.

When available, aspen communities offer critical feeding and bedding areas for summering herds where canopy is open enough to encourage understory development while still providing cover. Recent burn scars that have new green growth and are located adjacent to bedding and escape cover are great spots to find summering animals. Alpine willow-covered basins with a variety of other forbs and grasses are also good. Generally, summering elk and deer herds limit daily movements and often maintain a routine in order to conserve energy and pack on fat reserves for the fall. Summering bucks and bulls are typically much more visible and patternable.

In early to mid-August, bulls will finish growing antlers and begin to rub trees and brush to shed the velvet. Mule deer bucks are typically done growing antlers by mid-August and will shed velvet during late August and early September. As summer drifts into fall, grasses cure and forbs begin to dry out. Elk consume mostly dried grasses and begin to transition to some browse plants like mahogany, willow, aspen, and maple. Over the month of August and into the middle of September, the decreasing amount of daylight begins to initiate hormonal changes within elk. Testosterone increases in bulls, and an increase in melatonin in the blood stream induces estrous in cows. The pre-rut can be frustrating for hunters because bulls that were easy to find in early August will begin to cover vast amounts of country in search of cows. As cows come into estrus, bulls will compete for dominance and the opportunity to pass on their genes during the rut. Deer species utilize a polyamorous breeding strategy, where one male will typically breed multiple females. Contrary to popular belief, males compete for dominance and females ultimately select the most dominate male and the individual they want to breed with.

The month of October can be a very tough time to turn up a big mule deer buck. During this timeframe, mule deer will transition their diet to mostly browse species like bitterbrush, chokecherry, rocky mountain maple, oak, mahogany, and snowberry. Bucks will move into thicker cover and may begin to transition toward rut areas. Feeding is reserved for the first hour after light and before dark. The onset of the mule deer rut is also triggered by the hormonal changes brought on by the length of daylight. Generally, mule deer rut during the latter half of November into early December. The exceptions are the southern populations where they rut in late December and January. For elk and mule deer, most females will have been bred throughout the month following peak rut.

The physical demands of the rut are extensive. Foraging is a secondary thought to breeding, and males are likely to have depleted overall body conditions after the rut. Studies suggest that males may potentially lose up to a third of their overall body mass and weight. For both species, there seems to be a transitionary period after the rut where males move to find food and perhaps evade predation before eventually finding a pocket to spend the winter. Much like spring and summer, the winter months are spent in sexual segregation. Wintering female herds often move into low country or onto long windswept ridges and south-facing slopes. Diets consist of mostly dried grasses and browse. Bulls and bucks are more closely associated with rugged, remote, tucked away pockets that provide sufficient feed. Long burned ridges, sagebrush benches, and winter range habitat treatments are great places to find wintering herds. Mule deer winter almost entirely on browse species. If possible, males must recoup the weight they lost during the rut and maintain the energy levels required to continue to feed, evade predation, and maintain body heat. To do so, they move very little and feed for longer periods and more often throughout the day. Wintering bucks and bulls regularly return to the same area to winter. A late season hunt can prove difficult due to the terrain wintering bulls and bucks inhabit, but if you find one that you are keen on harvesting, typically you can find them day in and day out.

The spring months round out the cycle and bring the topic of discussion back to antlers. Over the course of the winter and into the spring, testosterone levels decline and the cells (osteoclasts) near the base of the antler reabsorb calcium, causing pitting and eventually deteriorating the base to the point that the antler drops off. Mule deer can shed their antlers from late January through March and even April. Elk more commonly shed their antlers throughout March and early April.

Antler growth is attributed to a combination of three things – age, genetics, and nutrition. Age is relatively easy to understand and explain. Simply put, a buck or bull has to live long enough to fully mature and develop large antlers. A mule deer buck is likely to reach his prime at age 5 or 6, while a bull isn’t likely to hit full maturity until 8 to 10. Does that mean a younger bull cannot grow a trophy rack? No, not exactly. Remember that there are two other contributors to antler development and a younger buck/bull with good feed and great genetics can grow a trophy set of antlers, although most wild, free-ranging animals must have all three.

Genetics are tough to understand in a wild, free-ranging population given that animals are often far ranging. There are areas where genetics seemingly play a bigger part in the antler size of bucks and bulls, but with age and great feed, a trophy buck or bull could potentially come from anywhere. We often assume that antler genetics are one-sided and we could control the antler development of future offspring by removing odd or unwanted antlered males from the population, but that’s not how it works. Genes are contributed from both the male and female, and without knowing what genes/ characteristics the female might contribute to antler development, it would be impossible to manage.

The most variable piece of the puzzle is year-round forage conditions. A buck or bull really begins building his next set of antlers long before the spring and summer months. Throughout the antler growth stage, a buck/bull cannot consume enough protein and minerals to both maintain body condition and grow the largest set of antlers possible. They increasingly must pull protein and minerals from body and bone reserves to meet those high demands, if indeed they have them. If not, antler size cannot be maximized and size will be sacrificed to maintain life. This is why it’s critical for those animals to have had good fall and winter forage and maintain or even improve body condition during those months prior to shedding and growing new antlers. I would even argue that subsequent years of favorable conditions need to be strung together to see maximum potential.

Antlers are composed of a combination of crude protein, calcium, phosphorus, and water. Growing antlers contain more protein than mineral, while finished, hardened antlers have more mineral content. Therefore, protein is particularly important during the first portions of the growing season (typically March to June) to maximize the growth in antlers that minerals will eventually fill in. Protein and nutritional content are greatest in new plant growth, and new growth is maximized when plants have the resources they need, which are water, sunlight, and soil nutrients. The best-case scenario for plant and thus antler production is mild, wet winters, spring rains, largescale seral (new) plant communities, and soils that are productive. This is why habitat restoration projects or even fires can be beneficial in the long run for populations and trophy potential. The removal of old growth vegetation frees up resources for new growth.

There are some general guidelines and considerations to think about when starting your scouting or hunting. Ideal habitat consists of approximately 60% forage areas and 40% cover, arranged in a manner that allows for open feeding areas, thicker thermal cover, and travel corridors. To survive and thrive, an animal has to have all the pieces of the puzzle. Deer and elk prefer edge habitats, areas that offer a lot of edge between two habitat necessities like feeding and bedding/escape cover. Water is critical; studies suggest that occupied summer habitat is often located within one-half mile of a water source. Mule deer may not be as dependent on water sources as elk, but it depends on how arid a location might be. In my experience, elk are likely to water every day during the summer and early fall months, while mule deer may only water every two or three days. If you are hunting an arid, more desert type landscape, focus your efforts in and around water and adjacent areas that have forage and cover.

During early season hunts, focus your efforts on finding quality feed. On the whole, bigger bucks and bulls seek out remote pockets far removed from pressure. Deer and elk prefer early successional plant communities to feed. Early successional plants are those that emerge first after some sort of disturbance. Fire, chainings, and other habitat manipulations that have had a few years to recover are not only good places to scout and hunt, but they can also produce the groceries required to grow trophy antlers. During the rut, bucks and bulls can occupy a variety of habitat types.


However, it often seems that males will attempt to push their harems out into more open spaces and milder terrain to keep them from competing males and assist in keeping track of the herd. In October, think about the forage mainstays for the species you are hunting and focus your efforts in those areas. Post rut, the name of the game is finding the remote pockets of vegetation and refuge a buck or bull may seek out to recuperate. For mule deer, think about areas with good browse, and for elk, consider grassy areas that are rugged, steep, and provide refuge from weather and predation.

The life cycle of deer and elk and the stages of vegetation and environmental conditions cause them to occupy different areas throughout the year. Take these factors into consideration this year as you research, plan, and hunt. It will make you a better, more successful hunter.