The Bear Necessities:
How Wild Foods Affect Bear Numbers, Harvests and Behavior
Ancient Saxons coined the word “mast” to define foods that are produced in natural habitats from trees, shrubs and other plants. These wild foods include “hard mast” (nuts) and “soft mast” (fleshy fruits such as berries, pomes and drupes). Hard mast includes acorns from the various oaks, hickory nuts, walnuts, beechnuts and even the small nutlike fruits of ironwood. Examples of soft mast include blackberries, blueberries, crabapples, black gum fruits, wild cherries, dogwood berries, greenbrier berries and grapes. Common apple, since its spread and establishment into the wild over many years, is now considered an important soft mast species. Mast conditions affect the reproduction, survival and hunter harvests of most wildlife.
The Division of Natural Resources (DNR) Wildlife Resources Section has annually surveyed abundance of important mast species in the Mountain State for the past 30 years. This information provides hunters the status of various wildlife foods which can aid them in their pursuit of game. It also helps biologists in evaluating how current and future wildlife populations will fare and assist them in forecasting hunter harvests. A total of 360 sites covering all regions of West Virginia were surveyed in 2000. Wildlife biologists and managers, conservation officers, foresters from the state Forestry Division, retired wildlife managers and biologists, interested sportsmen, and a Natural Resources Commissioner devoted their time to conduct mast surveys last year.
The mast survey in 2000 showed it to be one of the most abundant wild food-producing years on record. Biologists forecasted a higher overall bear harvest with a possible record gun kill. They also predicted a lower bow kill than in 1999. Their predicted harvests were accurate. West Virginia hunters killed a record 1,328 bears during the combined archery and firearms seasons. This combined harvest was 34 percent higher than the 994 bruins taken in 1999 and 23 percent greater than the previous record of 1,082 set in 1998. Gun hunters took a record 1,024 bears. This exceeded the 1999 firearms kill of 570 by 80 percent and is 25 percent greater than the previous record gun kill of 818 in 1998. The 304 bears harvested by bowhunters was 28 percent below the record archery kill of 424 taken in 1999.
How did biologists come up with such crystal ball forecasts? They had just completed and analyzed data that compared 20 years of mast data (1979-1998) with archery and firearms harvests during those years. They found that years with abundant mast resulted in high bear gun harvests and low bear bow harvests. Conversely, poor mast years showed low gun kills and high bow kills.
What causes this trend to occur? In years of plentiful mast, bears tend to go into dens later, making them more vulnerable to gun hunters in December. During years of mast failure, most bears enter dens early (prior to gun season) thereby greatly reducing gun harvests.
Mast conditions have the opposite effect on bow harvests. Bears roam farther in search of food during mast scarcities, which increases their chances of being harvested. Often when acorn crops fail, soft mast crops such as apple “hit.” When this occurs experienced archers select stands near apple trees where they have found bears feeding, thus increasing success. In years of mast abundance, bears concentrate their feeding and reduce their movement. As a result, archery kills are low.
The timing of hunting seasons is an important factor in how food conditions affect bear harvests, especially firearm kills. Gun seasons that are set before major denning occurs will show correlations to bow harvests (good mast = lower kill; poor mast = higher kill). Some states set seasons in September, October or early November, well before bears consider denning . In Massachusetts where an early firearm bear season is offered, biologists found that bears had increased vulnerability to hunters during poor mast years which resulted in higher gun harvests.
Mast conditions also have important impacts on bear productivity. For many years, DNR biologists have examined reproductive tracts collected from sows killed by hunters (both legally and illegally), as well as those killed as marauding bears, and by vehicles and other causes. They found evidence of breeding--fertilized eggs, implanted eggs and embryo development --regardless of whether mast was abundant or scarce. However, den checks of sows with radio collars during years of mast failure revealed no cubs.
Nutrition studies of penned bears in Virginia have shown that, regardless of the amount of food in their diet, all eligible sows produced cubs. Those with very low diets that simulated a mast failure, however, ate their cubs after giving birth. These would-be mothers probably had little or no milk to wean and raise young that eventually would have starved.
If a year of good mast follows a mast failure, then the vast majority of breeding age sows will produce cubs the following spring. Because sows with cubs skip a year in breeding in order to raise their young, high cub production occurs two years later and continues at two-year intervals. This phenomenon is known as production synchrony. A mast failure in an uneven-numbered year (as occurred in 1997) followed by a good mast year (1998) would result in banner cub production the next spring (1999) and initiate uneven-year synchrony. Good cub years would then occur in all successive uneven-numbered years until poor mast is experienced during an even-numbered year, or until cub production of first-time breeders (bears don't normally start having cubs until age three) starts to even out birthing years.
Knowing when mast failures occur, and therefore the even-year or uneven-year production synchrony, also helps biologists in predicting bear harvests. For example, 1997 was a year of mast failure. Biologists predicted a high bow kill and low gun kill. True to prediction, the bow kill was 423 while the gun kill was 263. Cub production from malnourished females was very low in 1998. The fall of 1998 produced abundant mast, and biologists noted high cub production in the spring of 1999. Cubs born in that year would not normally be legal for harvest until 2000, when they usually would exceed 100 pounds. Aware that an uneven-year synchrony now existed with a highly vulnerable yearling bear crop available for 2000, biologists could predict a potential record gun harvest -- assuming 2000 had good mast production to keep bears from denning early. Their prediction came true as mentioned earlier in the article.
DNR personnel predict that 2001, regardless of mast conditions, should not be a record year for gun hunters. The sows that produced high cub numbers in 1999 did not have cubs in 2000. The next “cub year” (2001) won't have yearlings available for harvest until 2002. If 2001 and 2002 are years of decent mast production, then look for another banner gun kill in 2002.
Mast conditions greatly influence denning behavior. Bears are not classified as true hibernators. They lack specialized fat and fail to enter the deep torpid state and low metabolic rates of true winter sleepers such as ground squirrels. When approaching bear dens for research purposes, biologists must still use stealth and caution if they want to be successful in gathering information.
The abundant food crop of 2000 kept most bears out late. In fact, the mild winter of 2000-2001 showed that, of radioed bears in Kanawha , Boone and Raleigh counties only females about to give birth denned at all. Radio tracking revealed that males and sows with yearlings moved throughout December, January and February. It appeared they only temporarily bedded down, like deer, during brief periods that coincided with winter storms.
Mast availability also affects what effects bruins have on humans. Bear deaths from vehicle collisions numbered 16 in 2000 compared to 24 in 1999. Lower road kills may have been due in large part to excellent berry crops in summer and heavy acorn and hickory nut production in the fall, which likely reduced bruin movements. Besides keeping bears in the woods and away from roads and human development, good food conditions in 2000 can also partially be credited with low illegal (six) and damage complaint (eight) mortalities .
Bear damage stamps are required of all hunters who pursue bears. Stamp sales are deposited into a bear damage fund to reimburse property owners for real and personal property damage caused by bears. Looking at damage claims the last five years, 1997--the year of mast failure--showed the highest amount of monetary claims -- $78,964. Each of the remaining four years had claims lower than $37,000.
In years of mast shortage, unintentional feeding of bears by people increases. When food is scarce, bears will move continuously, sometimes vast distances, until food is found or they find it not worth the expended energy and opt to den. Hungry bears often will become bold and invade human territory where they find dog and cat food, bird feed and garbage to fill their empty stomachs.
In Minnesota, radio telemetry studies have shown bears to be quite vulnerable following years of mast failure. One radioed sow with three yearlings was followed through the spring and early summer months after poor food conditions the previous fall. When approached by researchers, the yearlings were too weak to climb trees. The lightest weight yearling, a female, died from starvation within a few weeks after departing the den. Her death was followed a few weeks later by that of the heaviest yearling, a male. The last youngster made it into summer and researchers expected it to survive, but it died from malnutrition after berry crops failed.
In West Virginia, wildlife personnel have observed starving bears that have been literally “skin and bones” in spring months following mast failures. In 1983, following the mast failure in 1982, reports were common of weakened bears unable to walk along streams and roadside ditches. Two adult males weighing 26 and 35 pounds were examined, the latter eventually recovering. Two female yearlings, each weighing only nine pounds, survived their ordeal, illustrating the toughness and resiliency of this species.
A concern of DNR biologists is the effect that year-round dog training may have on bears following years of mast failures. The Wildlife Resources Section has little information on effects of dog training on bears or other wildlife populations in West Virginia. Individual bears have been killed illegally and inadvertently during training hunts. Cubs, yearlings and some smaller adult bears are sometimes caught and killed by hounds. Some adult bears receive injuries during dog training. In 1999 an adult male bear in Virginia died from liver trauma after falling from a tree after being chased. Although most dog-caused mortalities are probably underreported, biologists suspect these incidences are uncommon and may have little effect on overall bear numbers.
Wildlife personnel are primarily concerned with dogs catching bears weakened by starvation following a year of scarce mast (especially where both summer soft mast and fall hard mast crops fail), followed by a late spring green-up with another failure of soft mast during the summer. Upon exiting dens in March and April, bears usually feed heavily on green vegetation. If this green-up is delayed by a late winter, bears are in trouble.
The good news is that the annual mast surveys will provide information in sufficient time to warn bear hunters that malnourished bears will be vulnerable to dogs. Responsible houndsmen can then refrain from training dogs until bears recover.
The mast surveys coordinated by the DNR Wildlife Resources Section provide practical information for hunters and biologists. Armed with the knowledge gained from years of survey data, biologists can wisely manage populations of our state animal.