____________________________________
SURPLUS POPULATION:
A FALLACIOUS BASIS FOR SPORT HUNTING
____________________________________
David S. Favre Gretchen Olsen
Professor of Wildlife Law Researcher, B.S. (Biology)
Detroit College of Law Trinity University (1979)
Published by the
Society for Animal Rights, Inc.
It is the purpose of this paper to examine the nature of the surplus population argument which is often proposed by hunters in justification of sport hunting. It will be shown that the term "surplus" is misleading and that the annual cycle of animal population does not mandate or require the existence of sport hunting. In order to explain or justify this conclusion, it is necessary to take up the science of ecology and explain some of the concepts which are part of wildlife population theory.
In researching this topic an extensive literature search was made. Both of the authors were very surprised by the lack of scientific research dealing directly with issues of the impact of human hunting on wildlife population [2]. It was much easier to find vegetation surveys or hunter surveys [3]. While granting that scientific research in the natural environment is difficult because of the number of variables to be considered, it is still surprising how little research has been done to confirm the scientific theories found in the writing and literature of the area. Therefore, we are limited in large part to a discussion of theories and concepts rather than detailed field observation.
Growth of a population is measured in terms of natality or birth rate (synonymous terms) expressed as the number of new individuals produced per unit of time (natality rate) or the number of individuals produced per unit of time per breeding individual in the particular population.
The theoretical maximum birth rate of a particular species is directly related to the biological characteristics of the species. The characteristics are a result of the forces of evolution. Each species has had to adopt a particular survival strategy for their environment. One significant variable is the number of young produced per breeding cycle. With humans, one child per cycle is the norm, but occasionally two or three per cycle may occur. In the animal kingdom, the African elephant on the one extreme produces only one offspring at a time. Rabbits on the other hand can produce litters of 4-10 babies and quail may have clutches of 12-14 eggs.
In the natural environment, the frequency of the birth of young as well as the number of young per cycle are both dependent upon a variety of environmental factors. When food is available to the female in abundance, the number of births per cycle will approach the maximum for the species, thus, when rodent populations increase, the clutch size of owls and hawks also increase [5]. It has been reported that the conception rate of southern Michigan corn fed does was nearly seven times higher than among the doe fawns from the Upper Peninsula [6]. One report on white-tailed deer found that the productivity of the high-diet yearlings was an average 2.5 times greater than low-diet yearlings [7]. Conversely, if food is not available then there will be a reduction in the reproductive rate. The reabsorption of embryos in deer has been observed in time of poor food supply [8].
The number of litters or clutches produced per year is influenced by many factors including: the length of the breeding season, the gestation period of the young, and the fate of the preceding clutch or litter. In most temperate regions the breeding season is restricted so that the young are born in either the spring or early summer. This is not necessarily true in the tropics where species may or may not have distinct breeding seasons.
Clearly, the length of a species' gestation period affects the number of young produced per year. A species with a short gestation period such as the meadow vole (21 days) and the ability to breed immediately after giving birth can quite obviously produce more young per year than the African elephant that even under the best of circumstances produces only one calf every three or four years. (See figure 2.) Several birds, including many species of ducks, though they ordinarily do not nest twice a season, will do so if the first clutch is destroyed or dies early in the breeding season.
The minimum and maximum breeding age of individuals of a population also affect the number of young produced per year. Elephants for example under optimal conditions reach puberty at 11 years of age and give birth to their first calf at age 13. The mourning dove conversely, if spring hatched, is capable of attaining sexual maturity and having a brood of its own within the same calendar year.
The sex ratio and mating habits of a particular species will also impact the population rate. For example, a population of monogamous swans consisting of 25 females and 20 males will result in only 20 females nesting. In a polygamous species such as the white-tailed deer, however, if the population is composed of 10 males and 70 females it would not be unusual for all the females to become pregnant. Additionally, in several species such as the wild dogs of Africa where there exist social groups, only the alpha, or lead, female will be allowed to reproduce.
Thus, there are many factors which combine to determine the first part of the population formula for a species, the reproductive rate of a species being a combination of biological potential and environmental factors. The second portion of the formula, the death rate, shall now be considered.
As might be imagined, predators play an important role in determining population levels. Generally, the smaller an animal the greater the effect predation has upon it as a decimating factor. Thus, an elephant has very little to worry about but a rabbit must constantly be on guard for attack both from the ground and air. Predation though an important and widespread decimating factor rarely operates to seriously limit populations below their capacity to survive. Because of the "law of diminishing returns," no predator is going to expend more energy in the pursuit of a prey than it is capable of gaining from capturing it. Once a species' density reaches a low point, it becomes difficult for the predator to find members of the species to hunt. In this event, the predator will turn to other less desirable prey species. It must go elsewhere or it will starve. Since there are less of s species in the area, there is less intraspecies competition and thus the population level may increase if given a chance.
Most wild animals at some time are subject to various diseases and serve as hosts for numerous parasites. Often the host-parasite relationship is tolerated and causes little problem; for example, the brain worm, Parelaphostrongylus tenuis, which is found in the white-tailed deer. Harmless as it is in the white-tailed deer, when this worm is contracted by the moose it causes a fatal neurological disease known as "moose sickness." The disease occurs under unusual conditions where deer and moose occupy the same range with deer acting as the reservoir hosts. Under normal conditions, most animals have adjusted to the presence of disease organisms and parasites since they have evolved and coexisted over a long period of time in the same environment. It is only when the ecological balance is disturbed or a new disease is introduced to an area that unusual levels of death ensue. The local balance might be disturbed by very dry conditions which result in large numbers of animals congregating around the limited water supplies, increasing exposure to risk significantly. Of course, individual animals can become more susceptible to disease if they become weakened by poor nutrition or accident.
Besides weakening animals, accidents can be the direct cause of death. All wild animals are subject to accidents be they natural or caused by human activity. Fires, floods, falls, highway mortality, power lines, etc., all take their toll. Usually accidents are a small but constant decimating factor. Sometimes, however, an entire herd can be swept away by a flood. An example of this that recently occurred was the Mount St. Helens eruption which virtually decimated thousands of animals of various species.
Where man erect fences, builds roads or creates any other unnatural obstacles, he increases the hazards for wild animals. Animal-car collisions are a common sight on our highways [9]. For example, it has been estimated that approximately 19,000 car-deer accidents occurred in Michigan during 1980 [10]. The death count of skunks, porcupines, opossum and others is sadly familiar to all interstate travelers.
When weather patterns deviate from the local norm, it may act as a decimating factor. Tornados, hurricanes and tidal waves are one quick extreme which causes death; the other slower changes in temperature and rainfall may be as important. In the presence of unseasonable weather, death rates particularly among the young, who have fewer resources, would be expected to increase. Cold weather can cause death from exposure; lack of rain may cause death if water sources disappear. Long term weather changes, besides causing mortality directly, cause it indirectly. Prolonged drought or severe winters may affect the supply of food or water which in turn can either lead to starvation or being taken by a predator in their weakened condition. Weather tends to eliminate the weaker and less capable of a species, leaving the strongest to reproduce when favorable conditions return [11].
Another decimating factor that operates directly and indirectly is starvation. Many different factors may combine to bring about a state of starvation -- intra- and interspecies competition, weather patterns, and accidents or diseases which render an individual unable to find his usual food supply. It is often difficult to assess just how widespread this mortality factor is because once an animal becomes weakened from lack of food, it may fall prey to other decimating factors such as predation or accident before actually starving [12]. (See Figure 3 for summary of above factors.)
The final factor to be considered is human hunting. Modern man represents one of the few decimating factors which have the capability of reducing a wildlife population to very low levels and even to extinction (e.g., passenger pigeon) [13]. In the early history of mankind there was probably little difference between the predation of man and any other large mammal. Through the development of hunting technology, however, humans now possess many extremely efficient means for killing animals. The near extinction of the American buffalo will always stand as an example of the potential of individual greed unrestrained by any social, legal control [14]. Today while the number of animals killed can be astounding, 165,000 deer per year in Michigan alone, it is unlikely that this large decimating factor will threaten the existence of the species [15]. This is because in the United States the vast majority of the sports hunters abide by the regulations passed by the wildlife agencies in each state [16]. Because of their large numbers and different motivations, the human hunter must be considered in a separate category from other predators. The issues surrounding the propriety of this activity will be considered in a later portion of this article.
Carrying capacity can be given only for a particular point in time, for in the same area long term succession or shifting weather patterns will change the carrying capacity [20]. As time proceeds, the open land and vegetation which the rabbit needs will evolve into a forest. As this happens, the ability of the land to support other animals may increase. (See figure 5.) The present population of deer undoubtedly greatly exceeds the historical level before the arrival of white men. This is in large part a result of the destruction of the climax forest during the logging of Michigan with the secondary, replacement growth resulting in a much higher carrying capacity for deer. So long as humans keep cutting the trees, the climax forest will never be reestablished, to the benefit of those who wish high levels of deer population.
Now one final variable needs to be added to allow the discussion to reach the issue of hunting. All of the previous figures have been simplified in that they have not reflected the annual population changes. Besides the long term changes in carrying capacity, there are significant changes within the cycle of a year. Herbivores such as rabbits and deer are dependent on vegetation. Late spring and early summer would represent the high point of the carrying capacity. It is during the spring abundance that the young of most animals are born, maximizing their chances for survival.
Evolution through the force of the genes has adopted the strategy of multiple births during the times of high carrying capacity to maximize the chances of survivability. The genes for many animals have learned that because of the multiple decimating factors many must be born in order that a few survive the annual cycle. One study of quail showed that while e quail might have 14 young born each spring, only about 4.6 would be expected to survive the winter [21]. On the other hand, the elephant has only one offspring, but very few decimating factors operate upon elephants and the longer life of breeding elephants combine to assure the survival of the genes. The genes have also learned how many newborn can be supported by the higher spring/summer carrying capacity. Since each species does this, it is evident that many individuals will die on an annual basis as the carrying capacity is reduced, going from fall through winter.
In northern states like Michigan, the winter carrying capacity acts as the ultimate limiting factor on the population level of a species. Because of this, a Michigan program to increase deer population focused part of its efforts at improving the winter habitat. It is hoped this program will increase the carrying capacity for deer and thus shift upwards the annual population cycle of deer. (See Appendix B for full explanation of program.)
The various species produce the large numbers of offspring because history has shown this is the best way to assure the long term survival of the species. No scientific studies have focused on the issue of whether or not hunting by humans would kill the same individual animals which would be expected to die during the period of lowest carrying capacity. We do not know the long term effects upon the gene pool of hunting replacing other decimating factors -- although it must be admitted that the effect might not be observable except in very limited populations such as bears or mountain sheep.
No life form is wasted or unneeded as the term "surplus" would imply. Even when an animal is killed by natural decimating factors, in death it is a resource to other living entities. When the hunter removes the animals from the natural habitat, they can no longer be part of the natural cycles, thus perhaps reducing the carrying capacity of the area for other living entities.
A final consideration in this area is the propensity of humans to manipulate the natural environment to their own ends. One of the primary concerns of state wildlife managers is determining the carrying capacity for game species. In promoting the interest of the hunter in having abundant game to shoot at, there is a strong incentive to manipulate the environment in order to maximize the carrying capacity for the desirable game wildlife at the expense of others. This has become a significant part of the activities of the Wildlife Division of the Michigan Department of Natural Resources (see Appendix B for full discussion). Whether this is the wisest thing to do from a broader ecological perspective is difficult to judge with the present lack of scientific information. But many individuals would operate upon the premise that the least interference by man is the best course of action [23].
In concluding this section on "surplus" population, it should be noted that while an annual cycle does exist for most game animals, this cycle has existed since the beginning of time and there is no basis to support the claim that sport hunting is required to keep wildlife populations under control [24].
One must cast around for the alternatives, must seek out the proper questions to discover the answers and set the goals. In the area of hunting and wildlife control the duty to ask the questions and find the answers has fallen upon one agency within each state's bureaucracy. The titles vary from Game Commission or Fish and Game to Wildlife Division (as within the Michigan Department of Natural Resources). That the task has fallen upon these agencies is primarily a matter of historical development which is beyond the scope of this article [25]. This historical development has resulted in a certain narrowing of options, for the questions asked are not as broad as one might hope. The primary question asked by many within these special agencies would be something like, "How do we provide the best hunting experience for the hunters of our state?" The literature is replete with surveys of hunter desires and preferences in an attempt to serve these constituents [26]. Other questions might lead to different goals and programs. For example, if the question was, "How should society deal with the relationship between deer and humans?" or "What concerns and interests do the various groups within our state have about wildlife and natural ecosystems?", then a much broader discussion would be expected.
As an example, consider the management goals of the Wildlife Division in the state of Michigan. In 197I, the agency set as a goal the build-up of the deer herd so that by 1881 there would be a stable fall population of one million animals. To achieve this goal a substantial amount of funds and effort had to be expended by the Division to increase and improve the habitat which is best suited for deer. Deer and deer habitat became a focal concern of the agency (see Appendix B for full details of Michigan program).
This internal view of the role of the agency, to provide quality hunting, is unlikely to change from any internal thinking or pressure. Three factors support the status quo within the agency. First, as with most bureaucracies, individuals are hesitant to question their own ongoing programs. The questions raised are about how to do things, not what things ought to be done. Secondly, besides the normal bureaucratics most state game agencies have a substantial group of individuals who are strong advocates for the hunters of the state. They are not neutral, but very supportive of the hunting ethic and would not be expected to raise broader based questions.
Finally, and in many ways most importantly, is the funding mechanism. Most of the game or wildlife agencies are self-funded, that is, they are not dependent upon general state revenues as is every other agency of a state. The monies are derived from license fees within the state and from an assortment of federal funding programs (Robbinson-Pittman, Land and Water Conservation Fund, Migratory Birds, etc.) [27]. Since a large portion of the funds which run the department and pay the salaries are from hunters and fishermen, there is a strong tendency for the agency to consider itself not as representing and working for the general public but that they need only serve their financial sponsors, the hunters and fishermen of the state. If your financial support is dependent on the activity of hunting, obviously very few are going to question the ecological or ethical problems therewith.
If change of perspective is ever going to arrive at the game agencies, funding and political pressure are going to have to come from new sources. Only if these special interest agencies are forced into the political mainstream of social and financial debate will the broader issues be faced. How this might be accomplished is not within the purpose of this article, but the new directions which might be taken will be briefly looked at before returning to the focal point of hunting.
Undoubtedly, much could be said about all the concerns, but the remainder of this article will focus on the last one, for there is a growing debate over the propriety of allowing any hunting at all. This is a moral debate; it is not an issue of science or of wildlife management. Rather, it is an ethical issue for which society must decide what is acceptable conduct.
Science does not mandate an answer to the issue of hunting, neither does wildlife management for it will do whatever society demands of it. The issue of hunting has arisen in a conflict of human history and human ethics. It must be recognized that hunting is a historically accepted human activity. Without doubt, until very recently hunting was a necessity for human survival. While this may still be the case in a few areas of the world, for most hunters in the United States, this is no longer the necessity it once was. Given that hunting has been acceptable to society in the past, the burden is clearly on the opponents to hunting to persuade society to their point of view.
This is nothing unusual or unique; as societies mature, becoming more concerned about the ethics of their actions, the burden is always on those who seek the change. This was the case with the issues of slavery and women's suffrage. There were always arguments and past practice to support the status quo. In both cases, the ethical arguments eventually won out, blacks and women began their road to equality. As represented by these two examples, there was also a substantial price paid by individuals and by society in resolving the issues. While it is unlikely a war will ever be fought over the issues of wildlife and hunting, there can be expected significant commitment of human and financial resources toward the effort of change.
Most hunters would rather be left alone; claiming it is a personal decision, to hunt or not, and that nobody has a right to dissuade their decision. The same argument was undoubtedly made by the owners of slaves. No one forced you to own slaves, if you decided it was all right, then you should be allowed to do so. In other cultures and other times, what a man did with his wife and children were of no concern to society. We in the United States have made certain commitments about the rights of being a human, and society through its legal and ethical pressures will control unacceptable conduct. Physical abuse of wives and children, child labor and other negative infringement on humans previously uncontrolled are now unacceptable behavior. The historical cycle of ethical or moral concerns seeking to change human conduct is now being repeated in the area of human/animal relationships.
But what does all this have to do with the issue of hunting? Life, the respect for life, has been the underlying motivation for ethical arguments and new laws. granting that most prior examples deal with increasing respect for the right of human life, it is still the element of life which is fundamental. Life particularly non-human life, is deserving of our respect. Respect is not reflected in an activity which promotes killing on whim or for personal gratification. The unnecessary infliction of pain upon living entities is to show disrespect for all living things. This perspective of life and seeking to protect it is not particularly new. Jeremy Bentham and Albert Schweitzer raised these points a long time ago [30]. In addition to this historical concern with the ethics of human action upon individual animals, there is now an additional scientific concern about how human actions impact species of animals and entire ecosystems [31].
Animal life is not found in fairy tales or Disney productions. Life is difficult, intertwined with death, with pain, with the struggle for survival. This struggle for individual survival has over the millions of years developed the ecosystems and individuals now observed. The struggle has produced human beings through the process of evolution. We are now aware of two relationships with our fellow creatures on the planet Earth. First is the common basis of life itself, that the nature of life for the bear, mouse and bird are not significantly different from that of humans. Not to say that bears are like humans or should be treated as humans, but that as mammals we share commonality of birth, child bearing, pain and suffering, happiness, and death. Even if other animals do not possess the same awareness of self and life, we are aware and as with the unaware human infants if we respect our own life we must respect life in others.
Secondly, our tie to other life is through the existing ecosystem which supports all present life. Notwithstanding man's often expressed attitude that he is above and distinct from other living creatures on this plant, he is just as dependent on the ecosystems of Earth as is the oyster or the eagle. Humans are but on the threshold of understanding all of the intricate relationships involved in supporting life. Given that natural processes have operated effectively for millions, billions of years, it is rather presumptuous of humans to step in and say they know best. Nature, natural ecosystems and all the contained plant and animal life should be left alone to the fullest extent possible. Humans should interfere only for good cause shown, only where the interference is required, and some understanding of impact is available. The desire of hunters to kill birds or mammals is insufficient reason; it is not good cause shown. Where a particular animal is causing significant damage to human population interference may be warranted. The nature of the interference, however, could vary from building a fence , to capture, to killing.
Even when sufficient numbers of people express their opinion so that general permit hunting is stopped, deer and other animals will need to be controlled in various situations. Wildlife will not simply recede into a distant forest. There will still be problems that must be dealt with. But the difference will be that these problems rather than being a justification for hunting will have to be addressed directly by wildlife managers.
Bennett, et al. 1980. Experimental Management of Michigan's Deer Habitat, 45th North American Wildlife Conference, 288-306.
Hansen, Economic analysis of Michigan's deer range improvement program. Ph.D., Univ. of Michigan (1977).
Langenau, Non-Consumptive Uses of the Michigan Deer Herd. Ph.D.. Michigan State University (1976).
Verme, 1961, Production of White-Cedar Browse by logging, J. of Forestry, August, 589-591.
Wood, Deer Range Improvement Program, Michigan DNR, p. 2 (1978).
For a short but representative argument in favor of sports hunting, see Appendix A.
E. E. Langenau and J. M. Aldrich, Immigration, Emigration, and Return Rates Among Firearm Deer Hunters in Northern Lower Michigan, J. Wildlife Management, 45(2): p. 323, 1981.
E. E. Langenau and Phyllis M. Mellon, Characteristics and Behaviors of Michigan 12 to 18 Year Old Hunters, J. Wildlife Management, 44(1): p. 69, 1980.
Mark E. Tilton and E. Earl Willard, Winter Food Habits of Mountain Sheep in Montana, J. Wildlife Management, 45(2): p. 548, 1981.
D. F. Grigal and N. R. Moody, Estimates of Browse Size Classes for the Snowshoe Hare, J. Wildlife Management, 44(1): p. 34, 1980.
Vernon G. Thomas and J. Paul Prevett, The Nutritional Value of Arrow-Grasses to Geese at James Bay, J. Wildlife Management, 44(4): p. 830, 1980.
David Arnold, Characteristics and Cost of Highway Deer Kills, John S. Wright Forestry Conference Proceedings, Purdue University (1978).
Driven to extinction have been such species as the easter bison, the sea mink, the Labrador duck, the Caroline parakeet, the heath hen, and the passenger pigeon. R. McClung, Lost Wild American, p 28-53, 1969.
O'Roke and Hamerstrom, J. wildlife Management, 12(78), 1948, kept track of the reproductive rates of a deer population on the George Reserve in Michigan, and found that the lowest fawn crops were produced (38 percent) when the population was at its highest concentration. Many other investigators have reported similar results providing further evidence for this control mechanism. Verme (supra note 8) found that among prime-age does the sex ratios of the fawns born were substantially different from the high and low nutrition mothers. to these mothers of restricted rations, 70 percent of the fawns born were males. The well-fed deer, on the other hand, produced only 46.7 percent males. This could, he felt, be a natural mechanism by which the deer regulate their population. A limited fawn production in addition to a disproportionate number of male births would curtail the population on deteriorating range. Or, if the habitat was capable of sustaining more deer, higher productivity and a greater percentage of female births would result in an expanding population.
Richard Taber and Kenneth Raedeke, Population Dynamics, Wildlife Cons., supra note 13.
Michael E. Nelson and L. David Mech, Deer Social Organization and Wolf Predation in Northern Minnesota, p. 14, published as a Wildlife Monograph of the Wildlife Society, July 1981, No. 77. This study of deer with radio collar tracking suggests the following data for one annual cycle in Superior National Forest of Minnesota:
Summer fawn production 130 fawn per 100 does
November survivorship 113 fawns per 100 does
April survivorship (after winter) 42 fawns per 100 does
Also see Coggins and Ward, The Law of Wildlife Management on the Federal Public Lands, 60 Or L Rev. 59, 66 (1981).