|Society of American Foresters||International Society of Tropical Foresters|
Michael T. Mengak University of Georgia
Humans have manipulated wildlife populations for thousands of years. Early human objectives were to provide food, clothing, protection, and shelter to family and tribe. Modern wildlife management shares some of the same objectives and new tools are available for use by managers. Today, wildlife management is a blend of art and science. Managers gather information and make decisions to manipulate habitats, resources, and people in an effort to achieve human goals.
The understanding of species biology and application of ecological principles are crucial to successful wildlife management. While wildlife managers work with vegetation and animals, much time is also spent managing people. Think of a three-legged stool. Wildlife management includes the legs of habitat-resources-people. Remove one of the legs and the stool falls. Human goals in wildlife management include conservation, preservation, consumption, and non-consumptive objectives. Wildlife management is the legal responsibility of state government through fish and wildlife departments and several federal agencies.
Conservation is the wise use of natural resources while preservation is generally considered to preclude most consumption. Consumptive use of wildlife includes harvesting through hunting and trapping. Non-consumptive use includes activities such as ecotourism, bird-watching, bird feeding, whale-watching, and endangered species management. Wildlife species are often placed into one or more categories based on their utility to humans and methods of management.
Wildlife is often defined as all non-domesticated vertebrates. A wild animal is generally defined as not wildlife and not domestic but a cross or hybrid between wildlife and domestic species. This legal designation is important for law enforcement purposes. Domestic species occasionally revert to a wild condition and are called “feral”. Donkeys, horses, cats, dogs, and pigs are common examples of feral species that often require management. They can have severe negative impacts on native ecosystems. Endangered and threatened are other legal designations that label some species of wildlife. Managers may deal with several different types of animals but the goal is generally the same – too achieve human objectives.
Wildlife is considered to be owned by the people and held in trust by the state. This principle forms the basis of what is known as the North American model of wildlife conservation. This definition is in contrast to a European model where animals are owned by the land owner – often nobility.
Wildlife Habitat Management
All wildlife species need food, cover (or shelter), space, and water. Wildlife managers manipulate these resources to increase or decrease the population size in response to management objectives. Ultimately, all wildlife must meet their need for energy. Individuals must balance their energy intake with the energy needed to maintain physiological process and reproduction. Food can be provided through supplemental sources such as food crops and orchard plantings, bird feeders, or timber management. Agricultural practices may be used to plant crops for wildlife or forests may be burned, thinned or harvested in order to manipulate natural vegetation for wildlife.
Habitat management activities may increase cover or shelter. Such activities can include supplying bird and bat houses in urban environments, creating snags or brush piles for natural cover, burning or disking (plowing) vegetation to reduce density or change species composition. Wildlife needs cover for protection from the weather including wind, heat, and cold; protection from predators and competitors; and escape cover for resting and raising young. Adequate cover minimizes energy loss to cold and wet conditions and helps animals maintain a positive or at least neutral energy balance.
Wildlife also needs adequate space for hunting and securing food and other life necessities. If wildlife populations are too dense, competition between individuals will contribute to stress and could lower survival rates or reproductive productivity. Water needs are often met from natural vegetation and free-standing water such as ponds and streams but humans may supplement water resources through management by supplying bird baths and (in the western deserts) watering holes.
Space is important for wildlife as is the distribution of habitat resources. Nearly all animals have a home range – an area on the landscape where the animals can acquire the daily and seasonal resources needed to survive. Some wildlife species will defend all or a portion of the home range from competitors of the same species. This defended space is called a territory. Wolf packs and large cats such as cougars and bobcats typically exhibit this behavior. Territorial behavior may be apparent throughout the year as with predators or only seasonally such as when the adults are raising young as in Canada geese.
The distribution of habitat resources must occur within the range that an animal can traverse in a limited time. The home range of larger animals like deer can be hundreds of acres or measured in square miles for large carnivores like cougars and bears. It can be as small as a few acres for smaller animals like mice and small birds. All the necessary requirements must occur within this space or the animal will not survive.
But animals do not live in a two dimensional world. Habitat can be arranged vertically as well and many species of birds and mammals can utilize vertical components of the environment. Songbirds may feed on the ground, on the tree trunk, in the canopy or above the treetops. Deer, on the other hand, are restricted to a much small vertical space. Wildlife species can also divide the habitat resources temporally. Songbirds may feed on insects by day and bats may feed on the same insect resource at night thus fully exploiting the resource but reducing competition since each feeds at a different time. The components of an animal’s habitat including diet, feeding strategy, activity time, breeding season, social organization and many other characteristics define a concept wildlife managers call the animals’ niche. A habitat is the animals address while niche is the animals’ occupation.
Habitat management includes manipulating resources through the use of numerous tools and techniques. Wildlife may prefer young, frequently disturbed environments or old stable environments or something in between the two. Succession is an ecological concept that describes how plant communities change over time. Generally, a plant community has a characteristic animal community associated with it.
Managers manipulate vegetation to create a mosaic of successional habitats across the landscape. Fire, herbicides, machinery, and timber harvesting are tools used to change vegetation and manipulate habitats to favor or discourage certain wildlife species. Edge is the contact zone between two different habitat types such as a forest and field. Some wildlife species are adapted to use the resources found in edge habitats while other species prefer large unbroken tracts of undisturbed habitat.
Wildlife managers study the preferences and behavior of target species and take actions to meet the needs of the species being managed. Rarely can a single area provide all the resources for many species. Managers must decide on which species to favor on each area and manage the area accordingly. Across the landscape, many areas will provide habitat for the maximum diversity of wildlife species.
Resources are not equally abundant throughout the year. Insects and seeds are generally not available in winter in northern latitudes. Forage may become dormant or unpalatable. Animals are faced with resource availability issues on a regular basis. Some animals, like songbirds and waterfowl, migrate when cold weather reduces the available of insects, seeds, nectar, or open water. Bird, whale, and sea turtle migrations are often latitudinal and individuals may migrate several thousands of miles. Bats may also migrate but they often migrate to a common location for hibernation. Other animals (mammals and reptiles) hibernate alone or with a few other individuals. Elk are examples of large mammals that migrate in response to seasonal changes in food availability but their migration are often altitudinal. Elk use high mountain meadows in summer and lower valleys in winter. Caribou and bison are nomadic migrants; wandering over vast acreages in constant search for food and other life necessities.
Wildlife Population Ecology
Wildlife populations have tremendous capacity to increase in the absence of mortality agents. For example, two healthy mice can produce ten offspring in one generation. If half the offspring are female and each female produces ten additional offspring, the two original mice can reach a population size of 432 mice in just three generations! This is called biotic potential.
Biotic potential is limited by genetics (elephants cannot have 10 offspring in one litter) and modified by the environment and health of the animal (old or sick mice are not likely to have ten offspring). The environment plays a role in population increase as well. Abiotic factors such as hurricanes, flood, fire, acid rain, global warming, pollution, and avalanches are examples of mortality factors that limit population increase. Biotic factors such as disease, parasites, starvation, hunting, accidents, habitat loss, and predation are examples of mortality factors that also limit population increase.
Wildlife Population Management
Carrying Capacity - Wildlife managers try to maintain wildlife populations in balance with available habitat resources. The ability of a habitat to support any given level of wildlife is referred to as the carrying capacity of the habitat. When wildlife populations are below carrying capacity, resources are not being fully utilized. When populations are lower than the desired objectives, managers implement activities designed to increase reproductive output and survival. This generally includes habitat manipulation. Other techniques include legal protection for migratory or endangered species, captive breeding and release, and restocking.
Successful population management can result in wildlife densities that are too high for the available habitat. Wildlife overabundance can result from a sudden loss of habitat forcing individuals into less space or from successful reproduction in the absence of predators or other mortality factors. If the former is the cause, balance is often restored in a short time. However, if wildlife populations are allowed to grow in the absence of natural regulation from predators then undesired consequences can include overgrazing and habitat destruction, conflicts with humans, increased healthy and safety concerns, and sudden die-offs of individuals.
Overgrazing and habitat destruction by one wildlife population can result in loss of habitat for other species. Conflicts with humans can result in damage to human landscapes and property. Healthy and safety concerns can include disease and predation risks. Carrying capacity really has two components. Biological carrying capacity is the ability of the habitat or environment to support a given population size. Cultural carrying capacity is the tolerance humans have for a given population size.
For example, the habitat may be able to support 100 deer but if those deer are contributing to increase deer-automobile collisions or eating human landscape and gardens then the cultural carrying capacity is less that biological carrying capacity and management action is warranted. Action could include hunting and trapping, fertility control (although this is largely experimental with wild populations), trap and relocate programs (costly and often illegal), or introduction of predators. Each of these management tools has distinct advantages and disadvantages and each is not without controversy. Wildlife managers must work with other citizens and stakeholders to try to achieve an acceptable comprise solution.
Habitat Management –Habitat management may be one of the best ways to increase or decrease wildlife populations. Habitats can be created using the tools we discussed above. Habitats can be improved with fire and timber harvest or other techniques. For direct management, habitat must be acquired before management can take place. For management across broad ecosystems, the land must be owned by the government, or agreements must be made among mixed public and private landowners. Various incentives, regulations, or educational programs also may be used to encourage management by private forest landowners.
Habitat acquisition is accomplished through a variety of methods. The federal government and individual states can acquire land by purchase or donation. Non-government organizations also acquire, manage, and sometimes donate land for wildlife management activities. Funds for state wildlife management and habitat acquisitions come from user fees like licenses and specialized taxes on outdoor equipment. Only rarely do general tax revenues support wildlife management at the state level.
Wildlife Damage Management –When wildlife populations become too abundant, managers step into to resolve human-wildlife conflicts. Generally, when this occurs, cultural carrying capacity has been exceeded. Lethal and non-lethal methods are available for wildlife damage management. Public education may solve simple problems like raccoons eating pet food. A solution may be as simple as sealing the pet food in containers with tight lids. However, other conflicts may require more complex solutions. Habitat modification can be used to alter habitats and make it unattractive to nuisance wildlife. Exclusion methods such as fences or other barriers may prevent wildlife from causing damage. Another method may include chemical repellents which can be effective in certain situations. A final solution may require lethal control such as mouse traps and poison baits or sport hunting.
Wildlife management requires knowledge of species ecology, biology, behavior, and physiology. Additional knowledge of plant species, population ecology, habitat restoration, and ecosystem management is required as well. Wildlife management involves working with animals and people. Wildlife management objectives are people oriented and people driven. Landowners, homeowners, farmers, ranchers, outfitters, restaurants, motels, and other businesses may all rely on wildlife for a portion of their income, livelihood, and personal well-being.
Adams, C. E., K. J. Lindsey, and S. J. Ash. 2006. Urban Wildlife Management. CRC Press, Boca Raton, FL.
Anderson, S. H. 2002. Managing Our Wildlife Resources. 4th edition. Prentice Hall. Upper Saddle River, NJ.
Logsdon, G. 1999. Wildlife in the Garden: How to live in harmony with deer, raccoons, rabbits, crows, and other pesky creatures. Expanded Edition. Indiana University Press, Bloomington, IN.
Chiras, D. D., J. P. Reganold, and O. S. Owen. 2004. Natural Resources Conservation. 9th edition. Prentice Hall. Upper Saddle River, NJ
Posted 28 February 2008