Forest Faunal Systems

Chapter 9

Manipulating Populations

A population objective, N*_t may have been established. Sooner or later effective management requires that some approximate objective be decided upon. There may be physical, ecological, social, monetary, time, or other limits or reasons that prevent it from being achieved. The manager needs to communicate the limits to the agency, public, or client. The population abundance may already be at the objective or very near it. This too needs to be communicated since taxes or fees should be paid only for desired change or a continuing desireable condition.. A minimum difference-squared per-dollar is one success criterion for managers. (See CAP17.)

There are many techniques available for causing or allowing population change toward an objective. This awareness is a stark contrast to assertions that "habitat management is wildlife management" and that "animals are a function of their environment" The set of techniques that follows (based on Giles 1971) needs to be used creatively and interactively in a search for lowest costs and greatest gains. From among the millions of alternative combinations and sequences (permutations) (see CAP2026) the faunal system manager must select an optimum set of practices for a particular time and place. Fortunately for the manager, the large system has many equifinal states (the same number occurring at the end of many different pathways). From among these, the minimum-cost options need to be sought, recommended, and selected.

There is very little published research on the population manipulation methods. There are so many methods, the environment of their use is so variable, the controls possible for good studies are so limited, and the reporting methods so sparse that there is little hope for building inductively a strong predictive capability. I have confidence that a predictive capability can be built because it needs to be and because new conceptual and computational tools are available within game theory, artificial intelligence, and expert system (CAP54). There are two major needs. The first is to set seasons and the entire set of regulations in a "what if ...?" mode, a "Play" against nature. This is the a priori need. It presents: If this action ... then we get that result. The second need is a posteriori. When the data are in, then explain the situation that produced unexpected harvests or confirm an algorithm that was used and assure its continued use until data justify a change.

It is possible, it seems to me, to build, deductively, a predictive capability for harvests in an area. A general expert system might be created, but the inputs needed will be specific to each state or province, probably to relatively small areas within an area having common objectives and relatively homogenous land use.

The premises can be generalized and graphs used to construct local relationships which are known or believed in by experts and, of course, that are available in local data bases. Examples of a preliminary rule base may be:

RULE 1. The larger the area for which regulations are prescribed the less the managerial and administrative costs per unit area (Fig. 9.1A). {In the following figures are demostrations that the rules and principles of population manipulation can be expressed graphically. Approximations are needed. At least they can be used to develop expert opinion about likely relationships.} Very precise, very heterogeneous harvest seasons cannot be afforded.

RULE 2. The more homogeneous (the less diverse) the area, the lower the enforcement costs (Fig. 9.1B). Agents' time in learning the regulations and providing clarification, instructions and education is increased as regulations become more area-specific.

RULE 3. The larger the area the greater the variability in conditions of the hunt (Fig. 9.1c).

RULE 4. Only portions of a map area are hunted. These are largely a function of access and a zone related to edge ownership, access points, and to corridors (Fig. 9.1d). (See CAP22.) The manager can influence whether these access points (e.g., bridges or boats to public land) or corridors (hunter trails) are useable by hunters or other resource users.

RULE 5. Access is a function of land ownership and lands may be posted or not based on regulations and their effect on the owner (Fig. 9.1e). Incentives, education, memberships and other strategies may influence land available or, conversely, the amount that is posted.

RULE 6. Access is a function of road conditions as well as length of road. Trout streams that are bank-full of water may block fords and reduce access to a watershed; frozen roads with light rain may make back country areas inaccessible (Fig. 9.1f). This access varies with region (elevation, etc.) and by year.

RULE 7. Number of hunters is a function of a"bad weather index" (a non-linear cumulative ice, snow, rain, fog, temperature, and wind index) (Fig. 9.1g).

RULE 8. Hunters who hunt primarily for social reasons respond differently to a bad weather index than do solitary hunters. The proportion of each subgroup (based on hunting motivations) among the hunters influences hunting effort expended against a population .

RULE 9. Age probably less than sex, residence, and socio-economic class influences potential hunters dropping out as a function of the bad weather index.

RULE 10. The highest proportion of harvest is taken on the opening day of a season. Extending a season adds hunting opportunity without significantly increasing the number of animals taken. Closures for a few days create new"opening-day" responses by hunters, such that area B of the curve exceeds area A (Fig. 9.1h).

RULE 11. The number of forest animals removed by legal hunting is a function of the size of the population (Fig. 9.1i).

RULE 12. The number of forest game animals removed is negatively and exponentially proportional to the legal hunting hours (effort) spent (Fig. 9.1j).

RULE 13. Farm and forest game harvested per day is governed by the law of diminishing returns to hunters. Hunters starting each day of the season are proportional to change (real, apparent, or perceived) in harvests obtained.

RULE 14. In forests and exclusive of big game, fauna cannot be overharvested by conventional hunting techniques used in conventional hunter behavior.

RULE 15. For many species, the proportion of the population taken each year remains constant even though other factors change (another occurrence of equifinality).

RULE 16. Game scarcity increases demand or value (Chapter 4), especially for trophy animals, and may increase lawlessness or reporting bias.

RULE 17. With polygamous species, hunting of males rarely negatively affects population productivity.

RULE 18. Hunting of animals having wide distribution and high productivity can reduce fall (hunting season) populations to normal, unhunted, winter population levels.

RULE 19. Hunting of such populations may increase over-winter survival, vigor of survivors, and spring-time production of young due to available food and space per animal for the residual winter population.

Using local data and conditions, rules similar to the above need to be created. These include rules with graphs of harvest per hunter hour on each day of the season, hours spent per hunter with each type weapon, hunters per vehicle, etc. The need is to characterize the hunter and his or her effectiveness. An expression of the vulnerability of an animal to each type of hunter (characterized as above) or the effectiveness of each type of hunter is a needed and not-difficult-to-get statistic. This estimate requires studies of the numbers of hunters afield (the same analyses apply to other resource uses) with weapon type x for how many hours and the proportion of each effort that resulted in (1) a reported legal harvest and (2) a reported loss. Eventually, the forested area manager will be able to estimate very well what an hour of y-type hunting by 100 z-type hunters with w-type weapons will harvest. The y-type hunting includes the factors of weather conditions, equipment, aids (e.g., dogs), group size, prior experience as a group, etc. The z-type hunter is the person in a class based on sex, age, experience, visual acuity, education, familiarity with the area, etc. With such information, the manager can (a) allocate hunters (i.e., effort) to take the desired number of animals, or (2) (at least) explain differences in harvests between years as a function of the precise hunter effort (and not by some appeal to mystical variance or the bitchiness of Mother Nature).

Permits can be a very precise way of regulating the harvest but with knowledge of hunts, a decided-upon number of licenses can be issued, or at some point in the license-issuing sequence, licenses only for weapon type x might be issued to produce the desired harvest. It is not unlike characterizing the size of fishing nets and the operating efficiency of boats in fisheries to learn about the take. Past studies of hunters have failed to use the power of the computer. Rather than reporting average take by males, then average take of people with shotguns, the computer should be used to isolate all of the people having all possible categories (in some cases this results in only one or two people in a class). For example, there is a group of males, of age class x, non-resident, solitary hunter, with greater than 3 years of experience, using .30-.30 rifles.

The area or methods available to the manager for regulation are numerous. The naive beginner wants to be told what to do. There are no instant answers, no managerial pills. The uses to be made of the following list of methods are akin to those made by the good doctor. A conservative change is made; the results evaluated, another change is made. The manager is the clinician. Responses are often slow; desired sets of options are difficult to enact or implement due to resistance of the public. Others cannot be continued long enough to get analyzable results. Controls are difficult to establish. Just because some actions on the following list have not worked in some areas (given the environment when attempted), there is little reason to reject them, generalizing from a sample of 1 or 2.

The list is presented as a checklist and as the set of opportunities for decisions about processes. They display most of the known options to the manager who may add to the list and then face the decisions of selecting the set of actions from many permutations.

As an example, a manager might look at hunter age in the list and have stimulated in his or her mind a proposal for a hunt for aged people in a particular area (location), during a 3-day period (time), using black powder rifles (weapons). The idea might be planted; the regulations drawn; the support groups encouraged; the resistance defused (e.g., by alternative hunts for them in time and place). The idea may not meet stated objectives; however, it may cause objectives to change. These are all possible consequences of creative, vigorous use of the following list. From one perspective, if desired change does not occur, the manager has not managed. The manager who takes an average or accepted strategy will, on average, be wrong. All sites, all populations, all managerial situations are unique. To fail to attempt to design a strategy optimum for that unique situation is to resign to suboptimization. The forest faunal resources deserve better.

Here are the tactics for thoughtful action:

Manipulating Fundamental Structure and Population Dynamics - Non-Hunting or Trapping

• Sterilize animals
  • Vasectomy
  • Castration
  • Chemo-sterilants
  • Mechanical contraceptive devices
  • Irradiation
  • Hormones
• Control primary sex ratios
  Virus or other pathogen
  • Nutrition
  • Chemical
• Modify ovulation rates
• Create hybrids
• Make purposeful genetic selection
• Release genetically engineered animals
• Modify the age of maturation, e.g., earlier maturation by higher nutrition
• Modify the proportion of the population copulating, e.g., by selecting hunting season dates

  Directly Manipulating the Population (Other than by Hunting or Trapping)

• Manage predator populations
• Manage buffer species populations
• Regulate diseases and parasites
• Regulate intermediate hosts of pathogens, e.g., molluscides
• Use entanglement techniques, e.g., adhesives on bird roosts
• Use detergents, e.g., surfactant solutions
• Use poison
• Employ poison gases, e.g., for bats, woodchucks
• Harass animals pre-season or inter-season to change average hunting kill
• Conduct shoots or culling, e.g., elk harvests by rangers

  Manipulating Population Behavior

• Use repellents
• Use scarce devices
• Use attractants
• Do buffer feeding, e.g., providing an additional, less valuable food supply to take feeding pressure off a desirable food
• Do vanguard feeding, e.g., pre-stocking release of predator-susceptible birds
• De-value or increase the"value" of the individual animal, e.g., rewards for numbered ear tags from bears
• Re-evaluate losses of benefits
• Alter behavior by diversions, travel lanes, fences, etc.
• Use enclosures
  • Fences
  • Rodent proofing
  • Protective containers
• Regulate the population around the threshold of the population-crowding or stress phenomena
• Change visual, audial, and olfactory contacts between individuals of a population
• Improve tracking and contacts by trails and olfactory aids
• Change line-of-sight between antagonists, e.g., nesting birds
• Change nest density to influence nest abandonment due to premature hen response to newly-hatched chick calls from adjoining nests
• Use hormones

  Influencing Movements Into and Out of an Area

• Control release, e.g., shooting preserve releases before the gun
• Stock from semi-wild populations
• Transplant from wild-trapped populations
• Introduce species new to an area
• Herd animals from horseback
• Use helicopter or aircraft herding or hazing
• Build barrier fences
• Build cattle guards
• Build fence baffles and breaks (big game crossing units)
• Encourage or build wire-fences with appropriate spacing for antelope
• Use trained dogs to harass or herd animals
• Build and plant drift fences and vegetation barriers
• Restrict human harassment during migrations
• Employ encirclement and drives

  Manipulating by Hunting and Trapping

• Regulate the type of hunter or trapper
  • Sex
  • Age
  • Resident, non-resident
  • Skill (past success)
  • Skill (marksmanship)
• Regulate the species to be hunted or trapped
• Regulate the number of each species to be harvested
  • Quota/Unit/Season
  • Daily limit
  • Season limit
  • Possession limit
  • Life-time limit, e.g., big horn sheep
  Regulate the sex taken, e.g., male, female, either sex antlerless, bearded turkeys
  Restrict age of animal taken, as correlated with
  • Body size
  • Horn growth
  • Longevity, e.g., old-age harvest of elk
  • Adult, sub-adult categories, e.g., in live-trapping removal
• Make appearance restrictions
  • Size (or weight)
  • Antlers or horns; beards in turkeys
  • Color
  • Pelage quality
• Restrict the location
  • Refuges and sanctuaries
  • Rest areas
  • Open areas
  • Hunt units, e.g., county, topographic, artificial
  • Blinds, hunting or trapping units, hunting points
• Influence access
  • Restrict by fences, gates, road barriers, signs
  • Create new access
    • Airports and heliports
    • Trails
    • Roads
    • Bridges (foot and road)
    • Boats
    • Snow vehicles
  • Provide game carrying services
  • Provide motorized travel services
  • Establish guide or packer requirements
• Regulate licenses and permits
  • Resident
    • Number
    • Cost
    • Availability
    • Land owner requirement
    • Age requirement
    • Animal or long-term
    • Ease of purchase
  • Non-resident
    • Number
    • Cost of permits
    • Availability
    • Age requirements
    • Ease of purchase
• Influence methods of take (similar to hunting or trapping)
  • Hunting practices
    • Drives
    • Stalks
    • Blinds
    • Towers, shooting platforms, and pits
    • Safety clothing and camouflage
    • Use of calls or broadcasts of calls or sounds
    • Use of attractants, odors
    • Use of baits and salt
    • Use of dogs
  • Weapons
    • Shotguns
    • Rifles
    • Pioneer weapons
    • Limit caliber and muzzle velocity
    • Limit shot size and bullet weights
    • Limit use of attached scopes
    • Limit number of shots, e.g., shell restrictions for waterfowl blinds
    • Archery
    • Limit pull or arrow cast
    • Limit arrow point or head specifications (including use of poison or drugs)
    • Limit to non-lead shell shot
    • Crossbow
    • Slingshot, etc.
    • Survival methods, e.g., snares and deadfalls
  • Types of traps, sets, and lures
  • Size of traps
• Restrict time
  • Starting time during day
  • Daily closing time
  • Weekend hunting
  • Sunday hunting
  • Starting date
  • Length of season
  • Interrupted season
  • Variable-length seasons (closing when desired number is taken)
  • Allow or prohibit if snow or forest fire danger is present
• Influence hunting or trapping desire and efficiency
  • Use education
  • Issue signs, signals, announcements
  • Provide hunting maps
  • Provide sighting-in grounds
  • Provide firing lanes free of cover
  • Provide trails and fence crossings
  • Provide bridges, fords, and other access
• Conduct enforcement
  • Use checking stations
  • Engage in violation-deterrent activity
• Control road accidents to animals
  • Use animal scarce devices
  • Place warning signs for autos
  • Fence
  • Close roads
  • Reduce vehicle speed
  • Use vehicle speed barriers
  • Remove cover along roads
  • Channel animals to protected or preferred crossing areas

Almost all of the above have been used in some form. Reports of them are scattered and the list has been gleaned from the technical literature, the popular press, and by observation. Perhaps the list is too sketchy to be useful. Some of the topics are covered elsewhere in the book. Each can be expanded as in the following major topics on licenses and permits.

Licenses

Response to license fee changes is highly elastic in the economic sense. License costs are generally so low that they rarely become a determining factor in whether a person hunts or not. In some areas, non-resident hunting licenses are sufficiently high (e.g., $500) so that they may have an influence, especially as they become a large proportion of the total cost of the hunt. (A non-resident living across the state line and hunting close to home may have low total costs; the high license fee may eliminate such people from a hunting population. A person with travel, room, board, guides, etc., would find the fee a small part of the total cost.) Questionnaires can be used to get expressed willingness to pay; experimental areas may be set where fees differ; interviews at checking stations may be used to get actual costs and expressed willingness to pay fees. Rates of change (not the actual amount) in expressed willingness to pay are likely to be useful in determining optimum licenses fees.

Group reaction to raising license fees can be very negative and politically hazardous so it cannot be easily tried experimentally among years. If a change is needed, at least a 3-year program of introduction, education, and support needs to be planned to avoid the almost assured political difficulties in gaining approval for the increase.

Permits

Hunters or resource users may apply for a permit. A random draw (CAP112) can be made and a set number of permits issued (CAP20). The relationship is straightforward. If you want a legal kill of 60 deer (H) from your management unit to achieve your forest protection and other objectives, then you issue permits to do so.

The bases for computing"60 deer" have been discussed in the previous chapters. A computer program is needed so the manager can respond to the unique characteristics of each population, needs of the area, and wishes of the resource users. Lacking one, then approximations about the proportion that can be removed and retain a similar population next year can be used (with great risk). These are shown in Table 9.1.

As an example of the logic and compilations, over several years you learn that from required check-out reporting that 23% (S) of your permittees are successful in taking an animal. To achieve a harvest of 60 animals (H), you issue P permits, where

P = 100 H/S

P = 100 (60/0.23) = 260

Table 9.1. Approximate annual proportion of removals from an average healthy population that may be taken and yet allow a stable population to persist.
Wild Turkey	0.33
Deer	0.10 - antlered bucks only 0.20 - 0.30 to hold herd stationary 0.30 - 0.40 to depress herd size
Rabbit	0.60 - 0.70
Squirrel	0.25 - 0.50
Bear	0.05 - 0.15
Quail	0.40

If you wish to remove 60 animals based on faunal space studies (whether reported or not) then crippling loss and poaching need to be included. Then, where H is the reported harvest, the total removal is H and

P = (CH/100) + (PH/100) + (100 H/100)

Thus, for example, where crippling loss (C) is 10% and poaching or non-reported kill (p) is 20% then

60 = (10 H/100) + (20 H/100) + (100 H/100)

60 = 130 H/100 = 1.3 H

H = 46

then

P₁ = 100 (H/S)

P₁ = 100 (46/0.23) = 200

Issuing 200 permits (not 260) will result in a total removal of 60 animals from the population leaving a number close to or on a planned trajectory to the objective.

This Web site is maintained by R. H. Giles, Jr.
Last revision May 10, 2001.