Basic Wildlife Management
Wildlife can be defined in many different ways. Some people include only game animals in their definition. Others include all mammals and birds. Most wildlifers (wildlife biologists or wildlife scientists) include all non-domestic animals and the habitats they depend upon as part of wildlife. Some even include feral animals like feral horses, burros, goats, sheep, as well as exotic wildlife species introduced into the wild.
Wildlife can be subdivided in many ways. Often these subdivisions are based on the perceptions or uses of the wildlife. Terms like big game, small game, waterfowl, upland birds and non-game wildlife are often used to identify a smaller group of animals. These terms are also helpful in assisting the biologist or manager in defining the tasks they are charged with performing for the society.
Wildlife Management
Wildlife management is both an applied science and an art. Its fundamental principles are applications of basic ecology, the study of animals “at home.” These applications are concerned with the basic needs of animals and animal populations, with the ways animals and habitats interact and with how living things share living space. These concerns include reproduction (the production of young) and recruitment (the entry of young animals into the breeding population). They also include mortality and population turnover rates.
In general living things produce many more offspring than would be required to replace the parent animals. If all these hopeful experiments in solving life’s problems survived, those species would soon dominate the earth. Like the example of the oak tree, however, most seeds pr young are lost in some way before they become mature. These excess individuals form a harvestable surplus that can be used without harming the ability of the population to sustain itself. Since the wildlifer is charged with maintaining wildlife for the society (at least in the United States, where wildlife is considered a commons resource, owned by all the people), they must treat harvest rates somewhat conservatively.
Wildlife management goes beyond the basic elements of biology or ecology, however. It includes the wants and needs of people as well. Those wants and needs vary among individuals, with a mixture of positive and negative attributes – aesthetic, economic, recreational, gastronomic, medical and others. Some people are satisfied to know that a species exists and continues to live in traditional places. Others wish to see wildlife or photograph individuals. Some people enjoy hunting, fishing, or trapping. Some view wildlife as dangerous, carriers of diseases, damagers of crops, killers of livestock or pets, eaters of landscape plants, potential causes of accidents on the highways or sources of income. Others look to their benefits to a vital and functional ecosystem or as potentially vital resources for future human health or well being. All of these viewpoints must be considered carefully and planned into the management of wildlife by those charged with that task as governmental agencies – usually state or federal wildlife management agencies.
Wildlife management may be defined in many ways. Aldo Leopold, the first formal wildlife management professor in the United States, defined it as wise use without waste of wildlife. In that regard, it is conservation or enlightened stewardship of the environment and the wildlife it contains. More recently, Giles defined wildlife management as the art and science of manipulating wildlife populations and the habitats upon which they depend to meet societal objectives. There are many other definitions, but all of them contain two basic elements: 1) the requirement for enlightened responsibility for wildlife and 2) responsibility to all people for the status of their commons resources in wildlife.
Principles of Wildlife Management
This is not a semester course in the principles of wildlife management, but it is designed to set out a few principles that lie at the foundation of managing wildlife populations, habitats, and human interactions.
All living things cope with limiting factors. They are bound by the amount of energy that can be captured from the sunlight and the chemical building blocks of life that come from the soil, water and air. The energy goes around only once and must be replenished from the sun. The "stuff of living things” is constantly cycled and conserved by the living things themselves and the geochemical processes that make them available to living things. These limitations may be gross ones – food, water, air, space, cover or shelter; or they can be fine ones like potassium or phosphorus concentrations or the availability of minute amounts of selenium in the soil. Regardless of the type of limiting factor present, something always limits the growth of individuals and populations.
Food is one of the major requirements of all animals. Since animals cannot capture the energy of sunlight directly, they must get their energy from plants, which do capture their energy and store it as chemical bonds, or from other animals. Each animal is adapted to use a specific type of food or foods. The availability and quality of the food available is a major element in controlling populations. These needs can be extremely specific. Browsing animals, for example, may not be able to survive on a diet of grasses, even when those grasses are abundant. They need higher quality food sources, like forbs or succulent shoots. Since food is required essentially all the time, its availability is an important limiting factor to wildlife. If food is abundant for most of the year but lacking in a critical time period, the animals may starve unless they have some way to avoid that time period. Some species may hibernate, aestivate or migrate to avoid food shortages. Others are adapted to store fats for periods of low food availability.
Water is critical to all living things. Some animals get all the water they need from their food or by drinking dew. Others must drink on a daily basis. If water is limiting, having an abundance of food or other requirements cannot allow the species to survive. All requirements must be met within the range of the animal for it to survive.
Cover is a broad term applied to all types of environments required to support the animal or population. Several types of cover can be identified. Breeding, nesting or brood rearing cover is used during the period when animals are nesting or taking care of dependent young. Its impact on productivity of young is easily seen. Many animals require secure areas to rest or loaf. This is not laziness, but conservation of energy for more important uses. It may be shaded area in the southwestern deserts or shelter from bitter winter winds in the far north. It is critical to survival. Feeding cover permits animals to gather their food effectively and with some protection from predators. Escape cover provides refuges from people, other predators, and conditions that tax the animal’s energy reserves too much. All of these types are included in the general term “cover.” It is critical that cover types be matched to the needs of wildlife if the populations are going to thrive.
The arrangement or pattern of habitat components is also a vital concern. The size, interspersion, proximity and accessibility of various types of v=cover patches or resources is a critical element in assessing the quality of habitat for a given species or group of species. Even the amount of space required by an individual is an important consideration in management. Mountain lions, for example, are very unlikely o occur at high densities because their behavior and hunting success requires relatively large amounts of space.
The law of the minimum states that for every population or species some factor exists in a minimum amount, this restricting the numbers of individuals or the growth of individuals in that species or population. If that minimum factor is supplemented, another factor will become the new minimum. Biological limiting factors may be obvious or very subtle, and may or may not be responsive to efforts to reduce or eliminate them.
Limiting factors interact to determine the carrying capacity of any given area of habitat. Although this maximum number that can be sustained on an area is constantly changing with the condition of the habitat, it is usually considered on a seasonal or annual basis. Generally, the carrying capacity for a given species is at its maximum during and right after the breeding season and at its lowest just prior to the next breeding season. If one considers a bucket with staves of different and variable lengths, the shortest stave at any given time (the limiting factor) determines the carrying capacity of the habitat. If seasonal conditions cause that stave to lengthen, another stave will become the limiting factor. Animals in excess of the carrying capacity must either move to new habitat or die. Where other patches of suitable habitat are not available or already saturated (the normal situation), death is the rule. These excess individuals may be taken out of the population for human use as well as through other forms of loss.
Biological carrying capacity is defined above, but the sociological carrying capacity is often lower than the biological one. Humans have traditionally attempted to extirpate (completely rid an area of) certain unwanted, feared, or nuisance species. Cockroaches, mosquitoes, ticks, house mice, and wolves have been subjects of extirpation campaigns at one time or another. People may regard raccoons, deer, beavers, muskrats, skunks, bats, snakes, or other animals positively or neutrally until one becomes a problem to them personally. For some species, merely being seen is adequate to define becoming a problem. These “out-of-place” animals may evoke fear or animosity because of destruction of property, fear, odors, damage to crops or landscape plantings, or fear of disease or parasites. They may become a problem because of accidents on highways or around airports. In addition to the perceptions of animal problems, the numbers of people participating in an activity or the conflict between people interested in using the same area for different activities must be considered as part of the sociological carrying capacity.
Although people commonly refer to the balance of nature and view it as a static entity, natural resources are constantly changing. That results in a dynamic equilibrium where constant changes counterbalance one another to give the impression of a steady state. If, for example, an area can support six cottontail rabbits, an observer may see six rabbits at the time of year where conditions are most limiting every year. Hundreds of rabbits may have been born, bred, and died to maintain that apparently static situation.
Management Options
Managers have several options for managing wildlife. Letting nature take its course is a management option, but one that has little support among wildlife professionals and the general public. It generally involves removing human beings from the management equation and attempting to maintain functional systems without using any management tools.
Manipulating populations is a second option. It is based on the notion that reproduction exceeds replacement needs, leaving a harvestable surplus. Since only a small portion of the young produced each year can be recruited into the breeding population and the carrying capacity of the land generally reaches a peak during the rearing season, surplus animals that would be forced to emigrate or die may be taken under a regulated harvest to allow people to use some of the over production for their own purposes. As the examples have shown, muskrats have the capability of increasing their populations by a factor of 19 while deer have the capacity to double their populations each year if no mortality occurs. Harvesting some of those species for human uses puts their collected energy to use for people. Regulating that harvest allows the species to maintain its productivity.
Reduction in population size takes place in many ways. Predation, starvation, parasites, diseases, natural catastrophes, accidents, and intra-species fighting area all common mortality factors. Hunting and trapping are human predation. This has been a natural mortality factor since humans became hunter-gatherers. Human predation changes the type, not the nature of predation. The only major difference is that humans tend to place limitations on their predations in the form of laws or ethical restraints. In many cases, all the mortality factors that are proportional to or dependent upon population size interact to maintain a fairly constant total mortality rate. This is known as compensatory mortality. In other cases, the population responds to higher loss rates by increasing its productivity – compensatory natality. In both cases, the populations remain at or near carrying capacity (biological or sociological) while allowing the use of a surplus population for other purposes.
The primary tools of the manager in working with population management are related to the control of harvest rates. These include the restriction of seasons, bag limits, types of equipment or restriction of the total take through the issuance of tags. Complex models that show the relationship between the probability of taking an animal and the numbers of tags issued may result in more tags being issued than there are individuals in a population. In that case, the diminishing returns or relatively low return per unit effort result in predictable harvest rates and population reductions.
Manipulating habitat is a more comprehensive means of managing wildlife. Most of the time, the objective in habitat alterations is to increase the population size, but decreasing habitat quality can reduce populations as well. Since habitat requirements are specific to each species or cluster of species sharing a habitat type, changing the arrangement of habitat components or the structure of the habitat or addressing the limiting factors for wildlife can modify the populations on a given site. As noted earlier, populations of wildlife usually will increase as the number of patches of necessary cover and the number of intersections of necessary cover increases.Since many game species prefer early or mid-successional habitats, setting back plant succession is a common tool of habitat managers. Often these procedures can be linked to other forms of conservation activity. Logging or farming can provide wildlife benefits. Fire or mechanical disturbance like disking or chaining an area can be used successfully to return an area to an earlier successional stage or to enhance the productivity of an area by returning nutrients to the soil.
Addressing limiting factors can be simple or extremely challenging. Where limiting factors can be identified easily, prescriptive changes in the habitat can be made to increase its carrying capacity. Planting cover or food plots, providing guzzlers for water in dry regions, constructing shallow impoundments or using fire or mechanical means to increase the forb production while opening up the ground cover are all ways to address limiting factors. Although predator control programs (like bounties) are seldom cost effective, under some circumstances predator management could be a valuable tool to recovery or enhancement of a wildlife population.
Where limiting factors are difficult to identify or the capability of the area to produce abundant wildlife is limited, attempting to address a subtle limiting factor may not be cost effective.
Regardless of the type of habitat management used, the wildlife manager recognizes the fact that he or she is actually managing a community. Seldom can we manage a single species without impacts on other species sharing their habitat requirements and preferences. The species of interest (game species, endangered species or others) is the reason for the management or the reason that a management program is undertaken. Associated species benefit from the same management program or activity. These species are managed as communities. They represent groups of plants and animals that share the resources of the community by maintaining a complex set of dynamic interactions.
Wildlife management is continuing to evolve as a discipline. Today’s managers are involved with understanding people and their motivations and satisfactions as well as wildlife and their requirements and preferences. The result is an integrated management system that takes into account wildlife biology, the capabilities of the land and water, human wants and needs, human pressures, economics and the political decision making process. While early managers could concern themselves primarily with biological limits and capacities, modern managers must include a broader spectrum including human interests and affordability as well as the potential impacts of selected actions. Professional competency demands state-of-the-art science, technology, and art. It requires enlightened responsibility for wildlife resources held in trust for the rest of society – supplying the professional wisdom for “wise use.”
