406 Wildlife Management indicator species is satisfactory, the entire system is operating adequately Keystone species are species that play an important role in the ecosystem These may be animals that hold most of the biomass in the ecosystem or that influence many of the other species or functions of the ecosystem In this way, if the population of a keystone species is removed from the ecosystem, the ecosystem changes dramatically Therefore, by managing only the population of keystone species, we are managing most of the ecosystem In recent years, species that modify the environment (termed ‘‘ecosystem engineers’’) have become a point of interest (VanNimwegen et al., 2008) Umbrella species are species that require a large area containing many types of habitats to sustain a viable population Often these are large-bodied homeotherms with large home ranges By securing a tract of land that is large enough to sustain a viable population of these species, many others will come under the same protection The focus here is on leaving enough area for the umbrella species and other members of the ecosystem, but there are no direct management implications for this approach techniques Techniques for managing wildlife are aimed at studying, reducing, increasing, or maintaining the population at its current level while securing its integrity (i.e., preventing loss of genetic diversity, enhancing long-term survival, preventing epizootics, etc.) and the integrity of its ecosystem The techniques can be classified generally into two categories Applied techniques for manipulating populations by impacting survival, reproductive success, or distribution Techniques for studying, analyzing, and assessing population Many of the more common techniques are published in a series of Wildlife Techniques Manuals published by The Wildlife Society The first of this series, edited by Mosby, was published in 1960 The most recent issue (the 6th edn.) was published in 2005 and edited by Braun The manual covers five main topics: teaching and communication skills, study design and analytical techniques, investigational techniques, managing populations, and habitat management Applied Techniques for Managing Wildlife Control of Wildlife The everexpanding human population ensures that human– wildlife conflicts will continue Most of these conflicts are within the realm of damage to crops, equipment, and other assets Thus, a major component of wildlife management is wildlife control A good example is managing habitats around airports to reduce gull activity near runways that endangers aircraft during takeoff Often, damage caused by wildlife is a result of human manipulation of the environment, such as outbreaks of herbivores following the eradication of predators and high concentration of canids around human waste sites leading to outbreak of rabies Wildlife management strives to implement control measures in a manner enabling the other goals of wildlife management (sustained yield or maintaining biodiversity) to be met The four processes necessary for wildlife management generally apply to wildlife damage control, with some differences These processes are the following: (1) Defining the problem The species causing the damage must be identified, the type of damage determined, and extent of the damage evaluated (2) Knowledge of the general ecology, behavior, and dynamics of the species causing the damage must be obtained and evaluated with special regard to its response to various control techniques (3) The combination of (1) and (2) defines the methods that are feasible and economical to control the damage (4) The methodology used must be evaluated Unless the cost of control is less than the losses due to the damage, management should not be implemented Wildlife Management Techniques Because wildlife management is an applied science, methods and techniques for both research and implementation are important As a result, a considerable amount of research has been directed at developing, assessing, and improving Applied techniques may be resource (habitat) manipulation, mechanical, behavioral, immunization and immunocontraception, biological, and direct population control Habitat and community manipulation: This refers to managing target species by impacting important resources and other species that interact with them (i.e., habitat manipulation, or impacting predator–prey relationships and competing species, and species that are ecosystem engineers) By controlling key elements that affect the species abundance (water, shelter, predators, etc.), it is possible to manipulate its density and distribution The increase in computer power enabled the use of spatially explicit models and Geographic Information Systems techniques to project the impacts of various habitat manipulations (Verner et al., 1986) Mechanical: The simplest and most successful method of controlling wildlife damage is exclusion by fencing The advantages of fencing are that it is relatively fail-proof and nonlethal However, it is expensive and labor intensive, demanding constant upkeep Furthermore, fencing large tracts of land is a major cause of fragmentation Behavioral: These are modern forms of scarecrows that operate on the animal’s senses and are, therefore, acoustic, olfactory, or visual A good example of visual repellents, other than the classic scarecrow, is the silhouettes of birds of prey that are placed on large glass windows to prevent other birds from slamming into them Examples of acoustic deterrents are gas cannons that produce explosions at irregular time lapses or recordings of alarm calls of other animals Ultrasonic deterrents work by using sounds at a high decibel level (above 120 dB), outside the range of human hearing, to cause a painful stimulus to animals with sensitive hearing, such as canids Olfactory repellents are chemical compounds Two types of chemical compounds can repel animals: (1) compounds that link a food source with an induced sickness through a behavioral process called conditioned taste aversion; and (2) compounds that repel through the unpleasant stimuli of the nervous system The first type are properly