Guide to the study of animal ecology

by Charles C. Adams

II. THE VALUE AND METHOD OF ECOLOGICAL SURVEYS

“I cannot too strongly emphasize the fact ... that a comprehensive survey of our entire natural history is absolutely essential to a good working knowledge of those parts of it which chiefly attract popular attention,—that is, its edible fishes, its injurious and beneficial insects, and its parasitic plants. Such a survey, however, should not stop with a study of the dead forms of nature, ending in mere lists and descriptions. To have an applicable value, it must treat the life of the region as an organic unit, must study it in action, and direct principal attention to the laws of its activity.”—S. A. Forbes. 1883.

Natural history surveys have come down to us from the early days of zoölogy. These surveys have been of many kinds and have ranged from the adventurous accounts of early and daring explorers to those of such naturalists as Belt, Bates, Wallace, and Darwin, onward to the voluminous accounts of the “Biologia Centrali-Americana,” and in the Challenger reports. These surveys have contributed greatly to our knowledge of the fundamental facts of zoölogy and to the training of naturalists.

The most frequent form of survey is that carried on along the lines which most nearly approach individual and aggregate ecology. Most of such surveys give only slight attention to the responsive relation, or only to its most general aspects. Surveys of the usual character are of great importance, and with students of taxonomic training and interests only, this form of survey occurs very naturally. Most of the governmental and state surveys and museum expeditions are developed along these lines. The frequency with which such methods are used in surveys, which are expected to produce economic results, indicates that these methods are generally considered the most satisfactory. The exceptions to this rule are mainly surveys of fresh and salt waters, and are related in some way to aquatic resources. Except when detailed individual studies of certain species or some special subject has been made, the usual form of the reports of such surveys is the annotated list. It is rarely that even brief chapters discuss the groupings of the animals as they are found associated in nature. These statements show that, judging from the past, the methods currently used cannot be depended upon for a rapid and symmetrical development of ecology, or for the best development of ecological surveys. These must be developed in a more direct and deliberate manner, by carefully planned and executed ecological investigations. It is desirable also that ecological surveys should be conducted along some one of the three main avenues of approach, individual, aggregate, and associational, in order that the science may develop symmetrically. The following are some of the reasons which may be mentioned in favor of such surveys:

As a record of the associations, their interrelations and responses to their environment—before they have become too much changed or exterminated. This is a duty to future naturalists and to future science. The animal remains in themselves are only a very incomplete record; their activities and environments are an essential part of the animals and should also be preserved.

The study of original conditions is a simpler problem than after interference by man, but excessive modifications result in the simplicity due to annihilation and a corresponding imperfection of knowledge. The value of a knowledge of original conditions tends to increase with time, and will aid much in future interpretations when there is still more disturbance. Thus an important perspective may be developed which will aid in estimating relative values. At the present time the loss of records of original conditions is only beginning to be felt. The possibility of making certain records will vanish with each generation. It is not even desirable to preserve all, but it is evident that many ecological records should be preserved.

As the importance of ecological studies, in natural environments, comes to be more generally recognized the serious encroachments of civilization upon habitats and associations is enforced upon us. Not only are the descriptions of these associations very few in number, but the interrelations of the animals in them are even less known, and the chances of preserving adequate records before their complete extinction are becoming fewer every year. Without the least disparagement of other lines of work, one can but wonder if the naturalists of the future will commend our foresight in studying with such great diligence certain aspects of biology which might be very well delayed, while ephemeral and vanishing records are allowed to be obliterated without the least concern. These changes are generally greatest where civilized man is most dominant, and in progressive attenuations, zones, or strips, the degree of change produced by him radiates. Ecology has developed only at a late stage in civilization, after much of the environment has undergone great changes, so that in order to study the original conditions, which are of such great historic and genetic significance, he must make long journeys, or invade the swamps or sterile uplands which man has not yet been able to reduce to the average conditions best suited to his needs. This state of affairs is one which, at times, makes him thankful that there are conditions which, for the present at least, man cannot cultivate and utterly change and mutilate. Some appear to think that an interest in such original conditions is of no particular scientific value, or is largely one of sentiment; still others, that such studies have no practical value. But if we come to consider that the original primeval conditions give us our best conception of the normal processes of nature and are comparable to the normal health of an organism, it puts the subject in another light. A pathological condition is, of course, a state in a natural process, as is also any disturbance of the normal order of nature by man, and each should be studied scientifically. But the science of pathology has developed best as a study of the disturbances of normal processes and is interpreted primarily in terms of the normal; and the artificial should be similarly interpreted—the natural being the basis to which all standards must be referred. A comparison may also profitably be made between natural conditions and the physiological and vital optima of organisms and to the responses which are made with departures from such conditions. Similar comparisons should be made in the study of the responses of aggregations and associations in natural environments and departures from them. No matter how much we learn, the normal must remain as the ideal, and all departures from and disturbances of such conditions must be interpreted in terms of this fundamental unit.

To study disturbed, artificial, and “pathological” conditions, without an adequate knowledge of the normal and original conditions of both the organisms and the environment, is an attempt to interpret the abnormal and artificial in terms of itself, rather than in terms of the normal. If, however, the normal is no longer preserved, then its nearest approach should be studied, but with all the more care and caution. With a proper understanding of the normal, the disturbances made by man will be capable of interpretation in an orderly sequence strictly comparable to that found in the original and natural conditions. The cutting down and washing of the lands, the draining and filling of depressions, the flooding of the lands, the destruction (or succession) of plant and animal associations (including crop rotation), are processes brought about or practiced by other organisms or animal agencies. An ecological standpoint gives us a consistent, comprehensive orientation of all these natural and “artificial” activities and processes, and shows the unity in all organic responses to the environment. Man’s influence in the main consists of hastening or retarding “natural processes.”

Naturalists have for a long time spoken of the “balance of nature” and of the all-pervading influence of any serious disturbance of it. This balance is, of course, only a relative condition, and not absolutely fixed. It swings from one side, then back, sometimes showing considerable amplitude in its swing, then again its moves are very slight, mere tremblings, as it were. But now and then some local catastrophic event occurs which overturns everything, as when a volcano becomes active, or some dominant association takes possession of the field,—as in the case of man,—and a new order is initiated and a new balance is developed. The mongoose in Jamaica, our English sparrow, and rabbits in Australia are the classic examples of the overturning of the local order of nature by the agency of other organisms. Obviously this balance is not a condition limited to any particular locality or group of organisms. Balance is very generally conceded to be of fundamental importance in the study of any species or group of organisms, if its place in the economy of nature is understood. A vast number of the problems of the economic zoölogist are thus problems, not so much of individual or aggregate ecology, but ones in which the balance of the whole local biotic association is concerned.

This was the fact pointed out by Möbius when he studied the oyster and came to see that it must be studied not in isolation but as a member of a community, association of animals, or a biocœnosis, as he called these interrelated organisms. These facts are mentioned, as examples from a vast number that are recorded, to show that our applied or economic zoölogy and entomology are fundamentally more closely related to associational ecology than to any other phase of zoölogy, and to suggest that it would be to the great advantage of the students of such problems if they clearly understood this relation. This is also an argument for the ecological organization of a vast number of natural history surveys, because the associational grouping of observations and responses gives the most intimate knowledge of the life of animals in the network of their environmental relations.

In addition to the balance of nature which is found within the small associational units there are the larger ones of considerable geographic extent, which the students of faunal or floral problems frequently call zones or distinct regions. Some of these are distinct ecological units, whose dynamic status should be determined, so that we may know and understand whether it is in a condition of stress, a process of adjustment, or one of relative equilibrium or balance. Under present conditions in what direction does it tend to move? At what rate? The non-ecological surveys have not put these questions or worked deliberately toward a goal which will answer them. For any comprehensive study of this character we need to have determined what may be considered as a biotic base, optimum, or balance, toward which relations under given conditions tend, and at which an equilibrium will become established (The Auk, 1908, Vol. XXV, p. 125). Such facts underlie all of the problems involved in the interpretation of climax biotic associations, and their application by man. Cook (1909, Bull. 145, Bur. Plant Industry, U. S. Dept. Agriculture, pp. 7, 8) has expressed similar relations as follows: “Unless we can form a definite idea of the original conditions we cannot expect to judge of their influence on primitive man, nor can we determine what effects man has had upon the vegetation and other natural conditions. We need what might be called a bionomic base line, an idea of the conditions which existed before man came upon the scene, the conditions which would again supervene if the human inhabitants were withdrawn.”

It is perhaps significant that the genetic or successional relations of habitats and associations, as contrasted with their descriptive classification, both in plants and animals, have in the past been developed, not by the ecological students who live and work among conditions greatly modified by man, as in parts of Europe, but in the newer, less modified America. In this respect a parallel exists to the development of our knowledge and the process and genetic interpretation of topography, which has also developed more rapidly in America than elsewhere. The process and genetic method which has developed in this physical science has now spread to the biological sciences and has found a fertile soil there for development on account of the relatively undisturbed biotic conditions which still persist in certain areas.

In this connection it may be worth while to indicate some of the ecological disadvantages under which the non-ecological surveys are carried on. As a rule, such surveys feel no strong obligation to record fully the conditions of the environment, or its developmental processes. The environment is considered as static, and not as a changing medium; it has no past or future, it has merely horizontal extension. The problem as to its dynamic status, whether in a condition of stress, in the process of adjustment, or in relative equilibrium, is not raised, or if it should be, it could not be handled. The student eager for new and little-known species is not the one to study such relations, at least, as a rule, this has not been his practice. So long as the success of a day’s work is measured by the length of the list of novelties secured, rather than by the quality and quantity of ecological relations discovered, such students and surveys will not contribute greatly to our knowledge of the economy of nature in the regions surveyed.

At the present time it is very difficult to secure trained men to do ecological surveying. Even a superficial examination of this paper should show that familiarity with ecologic methods and results is not one to be acquired offhand, but a knowledge which requires considerable special training; not only as much as is usually required for other kinds of zoölogical work, but generally more, because of its synthetic relational tendency which requires a broad knowledge as well as some special knowledge in several lines of biology and the allied sciences. Conventionally considered, a properly equipped physiologist must have a working knowledge of certain phases of modern physics and chemistry in addition to his grounding in biology. A properly trained anatomist should have a knowledge of physiological and developmental processes, or his anatomy is purely descriptive and static. A student of general zoölogy should be grounded not only in physiological and developmental processes, but also in the relations of the organisms to their complete environment. The ecologist requires also the grounding in physiological, developmental, and ecological processes of adjustment, but as well he must understand the processes by which the vegetation and the physical environment have been and are being developed and their method of mutual interrelations and adjustment. It is difficult for some students to develop the ecological phases in the field. There are many disadvantages to be overcome. The difficulties are similar, in some respects, to those of the ethnologist who is sent on some museum expedition. The wealthy donor of the funds may wish to see a room filled with specimens on the return of the ethnologist, so that materials which have bulk and make a showing take precedence over detailed studies of the habits, traditions, languages, and descriptions of the people, because such studies require appreciation rather than inspection for evaluation. The zoölogical student may meet with just the same kind of difficulty. His institutional authorities often judge values by the cubic foot and pound, rather than by the quality of relations discovered. The student himself who has had an extensive collecting experience, in which quantity and variety have been the ideal, finds it difficult to return from a day’s work with only a few pages of notes on the responses of the animals, and with perhaps only a few specimens.

With such an understanding of the general rules of the game we may turn to the application or art of ecology, to indicate its relation to general problems. With a grounding in the general principles of organic response to the total environment, one is able to see that the disturbances due to man are a problem in the adjustment of the highest type of animal, as a member of an animal association, to its complete environment. The “control of nature” for which men strive is the process of making the environments and associations to order. The disturbances in the natural order may be looked upon as so many huge experiments or trial activities in this process of adjustment.

If natural preserves are not made, how will the next generation be best grounded in the general principles of the science? Are these complex modified conditions the natural place to start the student, or should such problems be reserved for the maturely trained one? These disturbed fragmentary conditions may be likened to fragmentary fossils whose interpretation is attempted. A paleontologist whose only knowledge of animals was derived from such fragments, and who had never known a perfect living animal, would certainly be at a great disadvantage in such an investigation. The natural starting point therefore seems to be in as nearly natural normal environments and associations as is possible, and with such experience one is prepared for the more complex problems resulting from man’s activity.

By way of conclusion, some of the main advantages of ecological surveys are:

1. The record of natural environments and their associations for future generations.

2. The study of natural biotic conditions giving a perspective not derived in any other way.

3. The clearer conception of the dynamic relations of the balance of nature, biotic base, and climax associations.

4. Emphasis of the process and interpretative phase of scientific investigation over that of purely descriptive study.

5. Facilitating the invention of multiple working hypotheses which bear upon animal responses in nature.

6. Furnishing important conceptions to the study of the processes of adaptation and the struggle for existence.

7. Furnishing important general principles of great value in applied ecology.

8. Furnishing one of the best methods of learning how to get acquainted with the living aspect of the animals of any region.