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Predator Management

Predator management is a topic in the gray zone among public values, hunting and trapping, integrated vertebrate pest damage management, and population management. It is a controversial practice and may, in some situation, have undesireable secondary effects that are worse than the initial reason for initiating control. When predators or their populations are out of control they may affect recovery of species that are threatened or endangered. Predator control is expensive. If started, typically it must be continued. It is only recommended when:

• are not likely to involve an endangered species,
• costs and losses of predation are measured,
• real (not likely to change due to chance)
• significant to the land owner, and
• the costs are substantially less than the perceived losses.

A predator is a carvivore. All animals that eat other live aniamls are carnivores. The difference between predators and other animals that eat animals is that predators eat anaaimals in which a person has direct interest. When there is no direct interest, it is probably best to observe nature for there "things eat other things" regularly.

The modern manager is attempting to control damage, not injury.

When large numbers of an animal are needed or are to be produced, then losses need to be reduced ... and predator control is one such way. It must be continuous and viewed as a direct cost of operation. If done irregularly, it can result in great, usually undesireable fluctuations in both predators as well as prey.

The Fundamentals

Mortality is an expression of a loss rate. Natural mortality in wildlife populations is a numerical rate. It is one of the major dimensions of population dynamics. Deaths of animals result from many factors: starvation, disease, accidents, energy loss in severe weather, perhaps "old age" (but other factors like loss of vigor, sensence, and effects of poison disease operate), of course there is predation. Predators are only one of many elements, (no matter how conspicuous) that influecne population abundance. When a population of interest (e.g., a game animal) is part of a community and well established there, conventional predator control efforts will not increase that significant population. It is influenced by many factors of the environment and even though predation pressures may be lifted, the population will soon encournter other factors that limit abundance.

Predator action is believed to be, in most natural systems, mortality that is compensatory. This means, generally, that if predators do not kill animals, something else will kill them or they will die and the effect of the loss in the ecosystem will be about the same. Some biologists claim that predators remove the sick and old in a prey population. Predators are probably not very particular and seize any opportunity to take an animal. The more likely effect of predation is that when a prey animal is removed, the remaining food and other resources can be used by the remaining animals (i.e., more food per prey animal that remains in the system).

The story of predation is mixed and confusing because the predators as well as prey differ in their behavior, habitat requirements, and their reproductive rates (thus recovery rates). That foxes prey on mice does not elicit nearly the concern as that which is produced by their preying on rabbits. Some omnivores are predators as some time. It is useful to discuss the role of a species identified in a particular situation as predaceous, not a general class of behavior, and to discuss the probability of real, financial, measured loss.

When animal populations are not natural, i.e., when they suddenly (within a few years) have reduced feeding areas or when they nest in unusual places, then predation can cut into a population. (It is no longer "compensatory" but "additive.") Under such conditions when predators are attracted to such areas or reproduce and achieve unusual densities, then predator suppression (after suppression of effects (as by fencing)) may be used. Such direct predator population reduction has been effective in reducing losses to waterfowl and to endangered species where their populations, due to human involvement, are high. Again "prey determine predators" is the general rule. (There may be exceptions.) Sadly, from a financial viewpoint, most control efforts are costly and must be maintained and diversified for the suppression to continue. Reducing predator population effects is a cost of land use elsewhere that has typically produced the high prey populations.

Very intensive predator control using a variety of methods (including poisons) can reduce predators. Prey populations will respond, but that response is small and it is rare that unconventional, diverse, sustained predator population reduction is attempted. The costs are very high. One of the fundamental concepts of predator management is that in natural populations, prey determines the number of predators, not the converse statement. A general rule: the number of predators present is their response to a food supply, one with more energy taken in than energy lost or required to prey upon and process an animal. Net energy rules in the domain of the predator. Rarely do predators seriously reduce a wild population with high quality faunal space ("good cover") or habitat conditions.

Recommendations

The plan is to monitor predator and prey populations. When predator populations increase substantially (more than 50% from previous 3-year mean) and the effects of that change seem to reduce our ability to increase R(the system performance index), then and only then will control efforts be discussed and a cost-effective program possibly implemented. We seek balanced populations of predators and prey with both contributing to R. Excessive numbers of each may be "natural" but losses to many objectives (animal disease, economic stability, recreation sitings, safety, etc.) require action that results in the desired balance. The "desired balance" is difficult to decide and that is why quantified objectives are used and so carefully developed within The Trevey.

A program to suppress predator effects is to be implemented. Often predators prey on house cats and dogs, on penned poultry, and on animals on the range or pastures. The effect is the problem, secondarily the animal. We encourage as a first and almost final strategy the improved husbandry of all livestock including care, confinement, rotating feeding and watering areas, human presence, use of protection dogs, fencing, health maintenance, insurance, and rapid disposal of sick or dead animals.

Consider studying the general management practices outlined for animals. Most are provided to increase populations. Re-think each as it might apply to reducing the predator(s) with which you are involved. The reverse of the recommendations may be the action you need to take.

Then, and only then, do we recommend careful in-depth discussions of effective suppression of effects. Note, we have not yet mentioned killing predators. If a predator takes $500 worth of livestock, is it worth $600 to control it? We first argue for reducing expected financial loss. This is an economic expression, the product of (1) the probably value of a unit (e.g., a bushel), (2) the probable unites produced, (3) the probable proportion of loss of (2) due to animals, and (4) the probable price per unit. Is loss of a fawn deer in an area that is highly over-crowded with deer a loss that needs to be stopped? We suggest that is not the case.

We seek first to suppress conspicuous effects, then suppress expected net present discounted financial loss, then reduce unnatural situations such as animal feedlots, watering areas, and human constrained migration routes, then to prevent such occurrences.

Managing populations of mice or other small rodents, a prey base, is what is needed to meet the needs of some wild animal populations (called predators) such as the hawks, owls, foxes, and cats. Many predators are as prized as game animals and some are endangered. Thus they need all of the skills of managers once devoted to increasing populations of game species (most of which were plant-eaters). It now seems that predator management (to increase them) depends more on prey management than habitat management, though both are intertwined. Many carnivore populations have the ability to recover rapidly.

Our plan is to analyze objectives, express evident effects, suppress effects cost effectively, analyze residual effects, then use predator suppression where needed. In some cases a single animal or pair may be causing dissatisfaction. These will be removed, live trapped where feasible, and placed in an appropriate area. Usually there are no suitable areas; populations are at capacity, behavioral disruptions may occur in the population into which the extra animals are placed and and create problems for other people. Otherwise the animal will be dispatched humanely.

Like other animals, predators are a function of their habitat. Often conditions for them can be reduced.

After this, cost-effective populations suppression will be carried out.

No bounties will be used due to persistent fraud and ineffectiveness experienced with this practice. It is well known that bounties are not effective and should not be tried.

Trained suppression agents will be used.

Repellents (chemical) as well as guard aniamls (dogs,llamas, donkeys, etc.) may be considered.

Humane treatment will be emphasized.

A long term view (more than 50 years) will be used.

Significant change (as stated above) in perceived effects; not necessarily animal abundance, will be an emphasis.

Scent post studies and road-side observations will be used to establish population trends (for comparisons with perceived predation rates).

Multiple-predator species will be the first assumption that will be made until observations determine an alternative. That the predator populations are larger than evident will also be a typical first assumption. Seasonal shifts in home range and movement will be expected. Home-range overlap of individuals is expected.

A protect-the-predators project exists and Wildlife Damage Review is an anti-federal predator-control organization (PO Box 85218, Tuscon, AZ 85754 (520-884-0883))

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This Web site is maintained by R. H. Giles, Jr.
Last revision April 21, 2001.