Game Management

X. PREDATOR CONTROL

CHAPTER X PREDATOR CONTROL Attitudes and Policy. Predator control has received more attention than any other factor except hunting. This accords with the developmental sequence of ideas already explained in Chapter I. Unfortunately, much of this attention, and many predatorcontrol operations, have been based upon assumed or traditional predator-game relationships, or at best on generalizations supported only by a small number of observations which were, in the light of present knowledge, often misinterpreted. Our knowledge of the inter-relationships of animals is still very imperfect, and current interpretations of evidence are doubtless still far short of the truth. It may be said with assurance, however, that they grow nearer correct as time goes on. The game manager is under obligation to be guided by the best available knowledge in his predator-control policies, else the standing of his profession, and the welfare of the game, may both suffer. Predatory animals directly affect four kinds of people: (I) agriculturists, (2) game managers and sportsmen, (3) students of natural history, (4) the fur industry. There is a certain degree of natural and inevitable conflict of interest among these groups. Each tends to assume that its interest is paramount. Some students of natural history want no predator control at all, while many hunters and farmers want as much as they can get up to complete eradication. Both extremes are biologically unsound and in many cases economically impossible. The real question is one of determining and practicing such kind and degree of control as comes nearest serving the interests of all four groups in the long run. This assertion is no mere paraphrase of the" happy medium." The actual conflict of interest is not nearly so great as the several factions suppose. The complexity of the game-predator relationship is greater than any of the four groups suppose. In spite of this complexity, however, the actual measurement of losses from predators is thoroughly feasible, as proved by such work as 2]0 PREDATOR CONTROL 23 1 Stoddard's. As these measurements progress, the apparent conflict of interest is being continually whittled down and reduced to specific local issues, or sometimes even to no issue at all. Common sense usually suggests a way to act on these local issues, whereas in their generalized form the same issues appear to be in irreconcilable conflict. This chapter will attempt to picture as clearly as possible a mechanism of depredation, and to isolate as many as possible of its known working parts for separate examination. In order to keep our minds focused on the thing being isolated, the endless succession of ifs and ands which might be raised concerning its workings in special cases will be deliberately omitted. We are not referees to a controversy; we are trying to gain an insight into a complex phenomenon. We are not trying to render a judgment , but rather to qualify our minds to comprehend the meaning of evidence. What Determines Loss from Predators? Subject to the physical adaptations of each, the annual direct mortality from predators in a given species of game on a given range depends on five variables: I. The density of the game population. 2. The density of the predator population. (1 and 2 determine the game: predator abundance ratio.) 3. The predilection of the predator, that is, his natural food preferences. 4. The physical condition of the game and the escape facilities available to it. 5. The abundance of "buffers" or alternative foods for the predator. (5 in comparison with 1 determines the relative abundance of various kinds of prey.) The whole predator-game relationship constitutes a biological equation in which the predator must balance his predilections (3) against the difficulty of satisfying them (1, 2,4, 5). It should not be overlooked that this difficulty decreases as the game density goes up under management. It is also usually true that escape facilities commonly deteriorate with intensive agriculture. The last two variables in the equation (4, 5) fluctuate violently GAME MANAGEMENT with weather for reasons which will be explained later. In the case of migratory predators, the second variable likewise fluctuates greatly as between years. There are many indirect losses and gains from predators, some of which will be mentioned later. Standards for Measuring Loss. Losses from predators on any unit of range may be measured in three ways: I. The number of head of game killed by an individual predator during a...