Monitoring Game Crucial For Future Seasons

By George Pauley - Idaho Department of Fish and Game With another big game hunting season coming to a close, most hunters will no doubt engage in lively conversations over their season's successes and disappointments. Inevitably, these discussions will focus on the number of animals observed, trends in populations relative to previous years, and hunting plans for next year. As you might expect, big game managers spend considerable time working on these same subjects. In Idaho, wildlife managers have a number of approaches for monitoring big game herds, with results ultimately used for setting future hunting seasons. Aerial surveys are among a game manager's primary tools. Aircraft provide the means to cover an area and view most of the animals present. While some animals in dense cover are missed, a number of approaches can be used to estimate them. This gives the manager an estimate of the actual population, which is useful for setting appropriate harvest levels. Managers also use age composition estimates, such as the ratio of elk calves to cows, to index reproduction and survival of young. Age ratios are used to predict future population growth. Statewide, more than 1,000 hours of big game surveys are conducted annually to gather this information. Most of the effort is focused on elk and mule deer populations, while surveys for moose, mountain goat and bighorn sheep herds are more limited. With good information on animal abundance and population growth, managers also need to know harvest levels. The mandatory harvest report card that all big game hunters complete provides this information. Along with the aerial survey information, harvest levels provide an essential element for evaluating the impact of hunting on big game herds. In some instances, it also is useful to estimate survival and mortality rates. Idaho Fish and Game maintains radio-collared adult mule deer and elk in 16 study areas across the state. When the radio-collars send a mortality signal, researchers locate the dead animal and determine the cause of death. The data is used to determine death rates from causes including hunting, starvation and predation. Survival rates are calculated from the proportion of radio-collared animals surviving annually. Calves and fawns typically have lower survival rates, and the importance of various mortality agents are different than in adults. As such, calves and fawns are periodically captured and radio-collared in a sub-sample of the 16 study areas to measure their mortality and survival. Furthermore, fawns tend to have highly variable survival during their first winter, which is highly dependent on the severity of the weather. Each year, 200 to 250 fawns are radio-collared during December to measure the impact of the following winter. When all of these sources of information are considered together, they give Fish and Game a complete picture of how well Idaho's big game populations are doing. Because nothing in nature ever stays the same for long, however, Fish and Game must constantly monitor big game populations and adapt management strategies to account for changes in habitat and in wildlife and human populations. Hunting seasons are adjusted to modify harvest levels to change growth rates. In areas where the habitat can support additional animals, conservative harvest will allow herds to grow. Conversely, when habitat thresholds have been met or crop damage from big game is at unacceptable levels, the harvest can be liberalized to reduce the abundance to more appropriate levels. Monitoring big game populations is a complex process. But as times change, so will Idaho's big game populations. George Pauley is a research biologist with the Idaho Department of Fish and Game who is working on statewide mule deer and elk research.