This book has an unusual history. Most of the information included in it is the result of field studies by Anatolii Grigor'evich Yudakov, who was on the staff of the Laboratory of Vertebrate Zoology, Institute of Biology and Soil Science, Far Eastern Branch of the Academy of Sciences of the USSR. He was a native of the Far East whose life was tragically cut short on February 9, 1974. During the several years previous to his death, A. G. Yudakov, together with I. G. Nikolaev (though sometimes alone) conducted observations on tigers in the western section of the Central Sikhote Alin Mountains. Yudakov was only 36 years old, an energetic investigator, who was passionately involved in his work, and who was on the threshold of generalizing from the large set of unique data that he had gathered. This work promised to be an exceptionally brilliant one. Without question, A. G. Yudakov would have brought a contribution of fundamental significance to the fields of mammal ecology and wildlife management in the Far East of the USSR. However, these hopes and plans remained unrealized.
The misfortune that overtook A. G. Yudakov in the depths of the Sikhote-Alin Mountains, and that led to a tragic result, remains as an acute loss in the hearts of his friends and colleagues. But his death was not immediate. It was preceded by a courageous struggle for life, which A. G. Yudakov continued for over two days and nights completely alone in the taiga (and later for approximately another three weeks in a hospital under the care of physicians). His unusual strength of spirit in those days became known even outside his professional circle, and also far beyond the borders of Primor'e1.

Both A. G. Yudakov's scientific reports and the works published in his lifetime that were dedicated to the Amur tiger drew immediate attention.
The significance here was not only, and even not primarily, in the impressiveness of its subject. Much has been written and continues to be written about the tiger. These studies stand out for their unusual completeness, and the thorough analysis of the data that they contain, as well as for their fresh perspective on the phenomena investigated. They received a high level of appreciation from the most exacting judges: the famous Soviet mammalogists, N. K. Vereshchagin, A. A. Nasimovich, and G. A. Novikov. Somewhat earlier, V. G. Geptner, the greatest specialist on our cats and one of the initiators of the conservation of the tiger, became acquainted with the data of Anatolii Grigor'evich. This eminent scientist developed a very warm relationship with the young investigator. N. I. Kalabukhov, one of the most senior and the most authoritative among the ecologists of our country, who was working in Vladivostok at that time, strongly supported all A. G. Yudakov's investigations and was constantly concerned about the fate of the data that Yudakov left behind. Such unanimous support does not occur by chance. The representatives of the older generation saw in A. G. Yudakov a worthy successor in the best tradition of Soviet field ecology, the tradition of L. G. Kaplanov--the investigator who first dared to undertake the study of the life of the Amur tiger by means of tracking him in the snow.

The human side of A. G. Yudakov was also very attractive. A desire to create an impression on people was not at all characteristic of him. Naturalness and integrity were perhaps his main characteristics. He was a kind and sociable person, who always drew people to him.
It is just like this that his image, bright and infused with internal warmth, remains in the memory of all who knew him well.

1 Kucherenko, S. P. 1976. Yudakov's last journey. Okhota i okhotnich'e khozyaistvo (J. Hunting & Hunting Economy), No. 8, pp. 38-42

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The list of works by A. G. Yudakov comprises 25 titles, eight of which are post-humous. Ten publications deal with the ecology of the tiger, including problems of the methodology for censuses and the results of censuses of this animal. The total volume of published scientific works is not large. Short communications predominate among them, and also the range of topics is, at first glance, rather limited. But a close acquaintance with the publications of A. G. Yudakov will persuade one of the great diversity of his interests and of his broad approach to the phenomena under investigation. Among his ornithological works are communications on faunal discoveries, on the location of new nesting sites of species that are rare in Primor'e and Priamur'e, and ecological notes. From the latter, the most valuable publications were devoted to a remarkable endemic of the Okhotsk taiga, the Siberian spruce grouse ("dikusha" in Russian, Falcipennis falcipennis).

The data on the ecology of this bird were collected by A. G. Yudakov in his native places--in the upper reaches of the Selemdzha River. His predecessors in the study of the Siberian spruce grouse were famous naturalists of various generations: A. F. Middendorf, L. M. Shul'pin, L. G. Kaplanov, and K. G. Abramov, although the information from Analtolii Grigor'evich substantially enriched that which was known earlier, giving it a new meaning. This is true of information relating to foraging, nesting, and descriptions of the utilization of the territory by the offspring. His data dealing with the action of predators on the population of the Siberian spruce grouse are unique. And it is entirely fitting that the works of A. G. Yudakov are widely cited in a fundamental new monograph dedicated to birds of the grouse family1. The acuity of his naturalist's vision can even be judged solely by such a statement from this book as, for example: "The observations of A. G. Yudakov and the photographs taken by him show that the birds do not tear off the needles, but rather cut them off, accompanying this operation with a characteristic rotating movement of the head...The base of the needles remains in place, and there is a rather smooth edge to the cut" (p. 217).

1Potapov, R. L. 1985. The Order Galliformes, Family Tetraonidae. Fauna of the USSR, Volume 3, No. 1, Pt. 2. Leningrad, Nauka. Pp. 637.

But A. G. Yudakov was particularly attracted to the predatory mammals. One of his publications, which appeared in 1967, when his name first appeared on the pages of a zoological publication, was already dedicated to an evaluation of the predatory activity of the lynx (Felis lynx) in the conditions of Upper Priamur'e (co-author V. A. Dymin). He also wrote about the sable (Martes zibellina), which allowed him to translate into precise scientific language the information about this animal that he drew from his personal experience as a sable hunter. In a short article by A. G. Yudakov, prepared by him for the collection of papers: "Performance and Biological Productivity of the Hunting Grounds of the USSR" (Yudakov 1969), such questions are dealt with as the multi-year dynamics of the number of sables in the Amur Region, the rate of the sable's dispersal, and the effect of this little animal on the population status of its prey species and of its competitors. All the positions taken and all the conclusions of the work were supported by soundly-based citations of data.

In Primor'e, his first object of independent study was the Manchurian hare (Lepus mandschuricus)--a species that, up until that time, had received almost no special study. A. G. Yudakov had already begun working with I. G. Nikolaev with regard to this topic. In a very short period of time (1967-1968), they were able to collect data thoroughly documenting the biology of this little-known endemic of the fauna of Priamur'e. A long report, reflecting the result of the work on the Manchurian hare, appeared after the death of A. G. Yudakov (1974). Besides a detailed description of the dimensions of individual territories, foraging, reproduction, and other aspects of the ecology of the species, the investigators succeeded in making detailed individual observations, which, however, bore the nature of small zoological discoveries. Such is, for example, the information on "above-ground" refuges of the Manchurian hare in the hollow of a sloping, desiccated lime tree (Tilia spp.), or the fact that one of the most active enemies of the little animals is the Siberian ferret (Mustela sibirica). Or, finally, there is a case, which was established from tracks, where a hare was extracted by a wild boar (Sus scrofa) from the hollow of a dead tree and torn to pieces!

Such a successfully begun study of the Manchurian hare had to be interrupted, because a new task was presented to A. G. Yudakov and I. G. Nikolaev: to carry out a census of the Amur tiger in Primorskii Krai, and, if it turned out to be possible, also to add substantially to the information available on the ecology and behavior of this animal. During the summer of 1969, they traveled through a major part of Primorskii Krai on a motorcycle, substituting the direct and detailed questioning of hunters for the earlier practice of using a formal questionnaire for such censuses. In the winter of 1969-1970, a selective investigation of the most interesting areas was carried out through the work of the organizers of the census themselves. These routes also served as a stimulus for a focused study of the tiger in the following three winters. The manner in which this was carried out is described in detail in the pages of this book. Here, it is only necessary to emphasize that the information collected by A. G. Yudakov and I. G. Nikolaev did not simply amplify the data on the tiger, but raised our knowledge of this animal to a qualitatively new level.

At the beginning of their work, the main source of information on the ecology of the Amur form of the tiger species remained the pioneering studies by L. G. Kaplanov (1948). While giving this outstanding naturalist due recognition for his contribution, it is impossible not to note that many problems were only posed by him, but not solved. The extremely low population size of tigers from the end of the 1930s to the beginning of the 1940s, when L. G. Kaplanov conducted his observations, even determined the unavoidably fragmentary nature of the data. It is also useful to draw attention to the inaccuracy, which was repeated in a series of reviews and a report (cf., for example, Ognev 1951, p. 21)1 where it is stated that during the winter of 1939-1940, L. G. Kaplanov followed the tracks of tigers (emphasis mine-E.M.) for 1232 km. While, as is clear from the completely accurate formulation of the author himself (1948, p. 20), this is merely the total length of all the routes taken during the winter in question. An exact number for the distance tracked is not given, but, obviously, it is several times smaller.

The series of tiger footprints that was tracked during the entire period of A. G. Yudakov and I. G. Nikolaev's work adds up to a route of scarcely less than 1,800 kilometers. Even taking into account a series of conditions that substantially facilitated the organization of the tracking (the reasonably good frequency of base camps in the field and the possibility of maneuvering along forestry roads in an automobile), the extremely high intensity of the tracking is obvious. Now, it seems that A. G. Yudakov hurried, as if he knew that he had little time left to him. However, the novelty of the results, which were achieved by him with the active participation of I. G. Nikolaev, is determined not only by the significant volume of the data collected by them, or by the fact that the ecological situation has fundamentally changed over the previous thirty years. In this plan, the critical reinterpretation by the authors of all the information that was known earlier, and the courageous abandoning, if the facts lead to this, of some sort of fixed idea is also very important. And such ideas do exist in the literature, and they are founded by no means only on methodically irreproachable observations done by L.G.Kaplanov. The figure of the tiger, like, perhaps, no other animal in our fauna, was surrounded--as is felt even nowadays-- by numerous exaggerations, speculative descriptions, and even legends. Much of this has been accepted as true. Clearing away such extraneous features in order to reach the truth about the tiger was not easy, but the authors acted in precisely this manner.

1Ognev, S. I. 1951. The Ecology of Mammals. Moscow. Moscow Society of Naturalists. Pp. 252.

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For all those who were involved in the fate and the work of A. G. Yudakov, it was obvious from the first days after his death that it was essential to make the data that he collected the available to all by publishing them to the greatest possible extent. Some difficulties immediately arose that were connected with the completion of this task: the author's manuscripts, even as rough drafts, were quite few in number. A. G. Yudakov had succeeded in publishing, or had himself sent to the press, almost all that had been written in the course of a preliminary analysis of the data (i.e., thesis reports). His fundamental legacy consisted of field notebooks, which had not always been filled out legibly, that were in a cursive script that was difficult to read. Also remaining were outlines of plans - a dissertation that had been thought out as a wide-ranging, comprehensive monograph on the Amur tiger and popular scientific books. A literal realization of these plans, a reconstruction of the intentions of the author, has now become impossible. In the present circumstances, it is still necessary to seek out that method of systematization of the data that would reflect its distinguishing characteristics in the best possible way, and that would require time. A. G. Yudakov's scientific director, the head of the laboratory, G. F. Bromlei, in a letter dated March 10, 1974, which was addressed to me, raised the question only of the reduction of the "unfinished investigations" of A. G. Yudakov to "some form of publication".

Originally, a "minimal program" arose: to limit itself to a rapid preparation of two or three long articles, reflecting the main results of what had been done. However, the data in hand required by their very nature a careful, gradual examination. In the course of this examination, the necessity of preserving the details, the inadmissibility of simplification or of superficiality in the discussion of any of the issues raised became ever more obvious. It became clear that a monograph is the sole form of publication capable of ensuring the presentation of the data at their full value. A detailed outline of such a monograph was put together in 1977 in Moscow as a result of the joint work of I. G. Nikolaev and the author of these lines. But the main difficulty was, naturally, not the construction of the plan of the book. Its' writing was preceded by a long, many-staged analysis of the data, and this difficult work was wholly undertaken by I. G. Nikolaev.

Having been a full partner of A. G. Yudakov in the field investigations, and bringing to their total result a considerable personal contribution, he could evaluate the primary data with a complete knowledge of the subject. He had to make a fresh start with everything, since the analysis of the data, which had preceded the first short publications based on them, was not complete, in part being of a "sketchy" nature. Several of the numerical estimates, which A. G. Yudakov had produced as preliminary calculations, were substantially refined by I. G. Nikolaev. The interpretation of the notes in the field journals, the checking and re-checking of the quantitative figures, the compilation of numerous tables, the tracing of unwieldy large-scale maps and tracking diagrams--such was the content of the extremely meticulous work of I. G. Nikolaev.
Frequently, difficulties arose: small contradictions, obscurities, or situations that could be treated in two different ways were discovered. And in not one of such situations was the decision taken dictated by considerations of practical convenience, simply to save time, or, still less, for the support of a previously accepted idea. Even in the details, no attempt was allowed to coerce the data, thereby coarsening them. Thoroughness, objectivity, the checking of each detail--these are the principles by which I. G. Nikolaev was constantly ruled. In this, by the way, lies one of the causes of the fact that work on this book has extended over such a long period of time.

The monograph in its present form has been created above all through the work of A. G. Yudakov, yet it is still more important to stress that two sources are fortunately associated in this work: the field enthusiasm of A. G. Yudakov turned out to be multiplied by the unhurried, thoughtful scrupulousness of his co-author during the analysis of the information. Summing up, they produced a completely original work, which is full of interest, and the significance of which goes far beyond the limits of the task of the study of a single species, even such an exotic one as the tiger. This is connected mainly to the extensive and consistent use of the method of winter tracking. The work of A. G. Yudakov and I. G. Nikolaev is a new stage in the development of the field investigations of this type that have been traditional in Soviet ecology. It suffices to say that the authors are perhaps the first to approach the determination of the length of the tiger's daily travel with the necessary methodological rigor--a most important, very widely-used index, but one which has until the present time been estimated very arbitrarily, in any event for an animal with a multiphasic 24-hour rhythm such as the tiger.

The book does not undertake the task of generalizing from all the information that has been published about the tiger up to the present time. Such a departure from the original intention of A. G. Yudakov has resulted from the following causes. Firstly, the systematization of such heterogeneous data would have required far too much of an expenditure of time and effort, which would have still further delayed the completion of the work. Secondly, such a course of action would inevitably mean a partial "dissolution" of the data of A. G. Yudakov and I. G. Nikolaev in the total body of data, it would have led beyond the limits of a specific territory, of the actual time segment of a real population "cell". That would have been unacceptable, since the main goal of the multi-year effort consisted precisely in introducing into general scientific circulation a large and intact "block" of data in order to disclose it to the maximum extent. Although compilation of information on the tiger during the 1970s and 1980s was carried out quite actively, the results achieved by A. G. Yudakov and I. G. Nikolaev have not lost their lustre against the background of more recent works. Their value has even increased with time, since they have acquired the role of the main "reference point" for comparisons by recording the situation at the beginning of the 1970s. The changes that occurred later affected both the ecological conditions and the population size and behavior of the tigers. A detailed analysis of these long-term tendencies still needs to be conducted. It is very important from the perspective of the conservation of the species; however, it goes beyond the limits of the present book.

The monograph does not contain review chapters. As a rule, only sources having the most direct relationship to the theme are cited, in the main those appearing up until the mid-1970s. Possibly a more complete disclosure of the original data would also have served the structure of the book. An enumeration of the chapters in the traditional outline of an ecological "species" monograph is not appropriate. Questions that lay beyond the field of view of the authors during their field investigations are not discussed. The fundamental place in the book is allocated to a description of those aspects of the ecology and behavior of the tiger that the tracking method is most effective in illuminating: the utilization of their territories by the animals, their hunting behavior, and their feeding behavior. The chapters that treat these subjects, naturally, turn out to be the most interesting.

Thus, the monograph by A. G. Yudakov and I. G. Nikolaev on the Amur tiger--the second landmark study in our literature that is dedicated to this remarkable animal--was published after a long and difficult period of preparation. Of course, it would have been better if this had occurred earlier. But, even now the book bears a fund of novel results in its main sections. And, undoubtedly, it will actively contribute to the discussions, at times quite keen, which are developing just now on the subject of what is occurring with the tiger today, and what may await him tomorrow. Still more obvious is its enduring significance for the development of investigations on the problems of population organization in large predators, their roles in ecosystems, and also for the understanding of other, extremely subtle, aspects of the ecology and behavior of mammals. This is a genuine study, and everything genuine is fated to have a long life.

E.N. Matyushkin

From the Author:

The successful completion of the work on this book would have been impossible without the assistance of many people, among whom, above all, it is necessary to name the now-deceased Professor Gordei Fedorovich Bromlei. The very kindest words are merited for that support which, over the course of a long time, was shown to me by my friends and colleagues in the laboratory. I especially wish to thank the editor of this book, E. N. Matyushkin, who not only concerned himself with the fate of the data collected by A. G. Yudakov, but also took a very active part in the creation of this book. Together with him, an extensive summary plan of the work was discussed and prepared, and several chapters of the monograph were written. I am also grateful to the artist T. A. Eroshenko for having prepared the graphical illustrations for the book. I consider it my duty to express my recognition of the Ivanov family, Mariya Fedorovna and Nikolai Agapovich, from the settlement of Martynova Polyana, for the warmth and comfort, which we experienced in their home, whenever we happened to be in their village after completing our usual itinerary following tiger tracks.

I. G. Nikolaev

Chapter 1.
Tasks and Methods for Field Studies. Nature of the Resulting Data.

The first task in the investigation of the Amur tiger, which we began in March, 1969, was the clarification of the population size and distribution of these animals on the territory of Primorskii Krai.

Simultaneously, we evaluated the state of tiger conservation and collected data characterizing the interactions between the tiger and man (capture of tigers, illegal shootings, attacks by tigers on domestic animals and on people). In parallel, work on a study of the ecology of the tiger was begun utilizing the method of tracking.

Older information permitting us to judge the former population size of this animal in the Krai was very limited. N. M. Przheval'skii (1870), V. K. Arsen'ev (1947a, b, 1948), and N. A. Baikov (1925) noted only that the tiger was common from the end of the past century to the beginning of present century. Actual data on the numbers of tigers were first collected by L. G. Kaplanov (1948), who laid the foundation for the field study of the Amur tiger. Later, K. G. Abramov (1960, 1961a), K. F. Kudzin (1966), and A. A. Sludskii (1966) cited data on the population size of tigers. The article by S. P. Kucherenko appeared in 1970, in which he generalized from information coming both from the teams that participated in Eastern Siberian hunting inventory expeditions and from his own data for the period 1964-1969.

The census work, which was headed by A. G. Yudakov, was carried out from 1969-1970. From March to October of 1969, preliminary information (based on questioning people) was gathered on the numbers and distribution of tigers in Primorskii Krai [75% of the area of the Krai was investigated]. Particular attention was devoted to personal interrogation of those hunters, who had been acquainted with the area that they hunted for not less than 10 years. Indirect censuses of tracks were conducted during the winter season of 1969-1970 using nine field teams. Each team included hunting guides and the most experienced hunters. Over the course of 15 days, teams of three to four people simultaneously conducted an investigation of the main habitats of tigers according to a network of routes that had been worked out earlier. A team headed by one of the authors worked over the course of the entire winter season. In the case of well-defined footprints, the width of the "heel" (i.e., the big sole pad) of the front paw of the tiger was used as the criterion by which a track was attributed to a particular individual (Abramov 1961b).

For purposes of the rational organization of the census work, Primorskii Krai was conditionally divided into six districts: Southwestern, Western, South, Central, Northeastern, and Northern (cf., Chapter 2). In the majority of instances, the districts were delimited by non-forested areas or by the ridges of mountain ranges. Movements of tigers from one district into another were rarely or never observed.
This work also utilizes data from a census carried out by A. P. Kazarinov (Khabarovsk Joint Scientific Research Institute of the Far Eastern Branch of the Academy of Sciences of the USSR) along the basins of the Bikin and the Bol'shaya Ussurka Rivers; data from the Hunting Department of the territory of the Chuguevskii Cooperative Fur Industry for 1969-1970; information from the recording of tigers that was conducted by the state professional hunters and scientific workers of the Sikhote-Alin, Lazo, and Ussuri State Nature Reserves during the winter of 1969-1970; and data from 130 questionnaires that were received from hunters (containing information on encounters, dimensions of tracks, and the way of life of tigers).

During the analysis and comparison of these data, we succeeded in determining relatively precisely the number of tigers in a locality, the nature of their individual territories and their travel routes. In cases where it was difficult to determine exactly the number of tigers in a certain location, then the minimal number was chosen for use in calculations. The team under the direction of A. G. Yudakov carried out tracking of tigers in the basins of the Milogradovka (the eastern slopes of the Sikhote-Alin Mountains), Borisovka, Nezhinka, Anan'evka, Amba (south-west Primor'e), and Komissarovka (the western region of Primor'e) Rivers. While following the tracks of various individuals, a distance of 270 km. was traversed, of which 250 km. were walked by the authors (160 km. by A. G. Yudakov). As the result of this, the total length of the routes investigated comprised approximately 1400 km. The results of the tracking were utilized to check the correctness of the conclusions produced during the analysis of the census information.

After the completion of the census work, investigations of the ecology of the tiger were pursued from January, 1971, to November, 1973. During this period, observations were carried out on a long-term study site of approximately 2000 km2 in size, which consisted of the upper reaches of the Malinovka River Basin of the Bol'shaya Ussurka River (Central Sikhote-Alin Mountains). This sector, which is designated with a rectangle in Fig. 4, is located at approximately the center of the Sikhote-Alin sector of the geographic range of the Amur tiger. Field studies were carried out during the following time periods:

1971: January 13-February 5; February 10-April 12; and November 14-December 16.
1972: January 17-April 13; November 18-December 2; and December 8-30.
1973: January 5-March 7; March 21-April 20; July 31-August 6; and November 20-30.

During this time, approximately 1500 km. of "tracking" and mapping of tiger footprints were carried out; A. G. Yudakov himself performed 1285 km.1 of the tracking. The total length of the routes investigated amounted to approximately 8,400 km. We made our observations from year to year on the very same set of tigers: three males and two females, which had offspring during the time of the study. Particular attention was devoted to the following questions: 1) the ecological conditions of existence for the most northerly subspecies of tiger (snow, frosts, nature of the vegetation, topography of its typical habitats, etc.); the system of travels and the shelters of the animals, the general features of their utilization of their territories; 2) the role of the tiger as a predator in nature, i.e., an estimation of the effects of the tiger on the numbers of ungulates, the tiger's relationship with its competitors, and its significance for humans; and 3) characteristics of the behavior of the Amur tiger.

1 These are more accurate estimates of distances, differing somewhat from the results of preliminary estimates; in addition, the numbers presented refer only to the long-term study site, since A. G. Yudakov (1974) gave the total estimate of the distance tracked by them for the entire territory of Primorskii Krai.

It is possible to produce the most complete answers to these and other biological questions under our conditions only by means of tracking. The method of winter tracking has been applied by Soviet ecologists for a long time and for the study of various groups of mammals. A. A. Nasimovich (1948) gave the most complete characterization of the goals and methods for its use. If long-term, direct observations on one or another species of wild animal are extremely difficult or impossible, the significance of "tracking" methods greatly increases for their study. This relates, in particular, to the Amur tiger, which, as an inhabitant of dense forests and thickets, is very cautious and secretive. It is precisely in the Soviet Far East and in the contiguous parts of China that the range of the tiger extends into the region of winters that are reliably snowy. As has already been emphasized, "the possibility of seeing, in the snow, a uninterrupted and precise "shorthand record" of the postures and movements of this predator exists only here, and, in relation to the entire area of the geographic distribution, it is unique" (Matyushkin & Yudakov 1974, p. 12).

The honor of the first application of the method of winter tracking to the study of the Amur tiger belongs to L. G. Kaplanov (1948). Even now, the results of his investigations have not lost their scientific value. In addition to new data on the tiger, L.G. Kaplanov gave a quite detailed description of the methodology of tracking in the conditions of the harsh winters of the Sikhote-Alin Mountains.

The organization of tracking by the authors reduces to the following method. First, we created depots of food and firewood and laid down a supply of the equipment that is necessary for work in the taiga in base stations (in hunting shacks). Simultaneously, we collected information on encounters with tiger tracks in the long-term study area. Such information was provided by questioning hunters and truck drivers of the forestry industry, and by personally reconnoitering the routes. As a rule, we succeeded in discovering the tracks and in starting the tracking 3-5 days after our arrival at a permanent base camp. The authors' observations were carried out one at a time. We simultaneously followed the tracks of either one or two tigers, but in opposite directions: along the track and against the direction of the tiger's path.

On the routes, we walked with only a light load, counting on spending the night in hunters' shacks or in settlements. Overnight stops under the open sky were, as a rule, not planned and were relatively rare. During the journey, each person had his field notebook, a topographic map, a compass, a pedometer, a tape measure, a hunting carbine, two cameras loaded with black-and white and color slide film, a telescope, a lamp, a mess tin, and a supply of food for one day. The tracking continued until the coming of dusk, and we sometimes returned to the base camp after midnight. Often, half of the daylight time during the working day was taken up by getting to the site where the previous day's observations had been broken off. With such a method of organizing the tracking, the general losses of time in passage were great, but, on the other hand, the observers were guaranteed a good rest.

Beginning with the second field season, we succeeded in decreasing unproductive expenditures of time by utilizing an automobile of increased rough-road performance that had been assigned to us. The observers were transported to the shortest possible distance from the track; the reverse trip to the base camp was organized in the same way. The automobile was used for the discovery of places where tigers had crossed a road and for travel to the base huts.

Skis (without fur sewn onto the bottom) were used in the case of a snow cover depth greater than 40-45 cm. Moreover, they were only used on the trip to the track and on the way back after the tracking ended. We moved along the track of the tigers without skis, stepping into a footprint, with the skis gliding behind, attached to a belt by a tie. In this manner, the number of steps walked by the observer along the track was practically equal to the number taken by the tiger. In those cases where it was difficult to make sense of the tiger tracks, we walked slightly to the side, without trampling them. The distance was measured in footsteps in most cases. We utilized the pedometer for their estimation, the readings of which were periodically verified by means of a direct count. During the measurement of the distance to the hunting sites of the tigers, we used a tape measure and an estimate of the number of steps from memory (the pedometer was switched off). The pedometer was also, as a rule, switched off during travel outside of tracking of the tigers (for example, while searching for a lost track). Distances walked by the tigers along public roads were determined with a speedometer, and along abandoned roads with the aid of a map or by stepping it out. For scaling, we used the empirically established ratio: 1000 m. = 1350 steps by the observer.

The average rate of movement along the tiger tracks equaled 1.7 km./hr., with the maximum and minimum rates being 2.5 km/hr. and 0.8 km/hr. The maximum distance that we succeeded in walking along a track during an entire sunny day was 20 km., the minimum was 5 km., and the mean distance was 11 km. The mean index of daily tracking for all observation days equaled 7.8 km. During a snowstorm, the tracking, as a rule, did not cease, which allowed us to prolong the uninterrupted pacing out of the tracks of one animal. Forced interruptions were caused by the loss of the track or by the fact that the observer caught up with the tiger.

We followed tracks of varying degrees of freshness; we moved both along the track and also against the direction of the path of the tiger. We would begin tracking the footprints of a tiger that had passed immediately before us backwards in order not to disturb the tiger. The pursuit of these animals occurred after a break of one or two days. Out of the total distance walked along the tracks, 21% of it was for tracks that were 24 hours or less in age, 23% for tracking footprints 24-48 hours old, and the tracking of footprints that were over 48 hours old comprised 56% of the distance. During the tracking, we recorded any precipitation and its nature (snow-fall; light, newly-fallen snow; drizzle) and the direction and strength of the wind. We measured the depth of the snow cover, and characterized its structure (friable, dense, with a snow crust, thawing). We also noted direct encounters with animals--possible prey of the tiger, competitors, and scavengers. The path of the animal that we had under observation was divided up into sections according to topographic elements (valley, terrace, foot of a slope, slopes and crests of mountain ridges) and other features of the habitat. We singled out sectors walked by tigers under conditions that facilitated their movements (roads, paths). Notes were made directly at the site of the observation, in which case we wrote down the reading of the pedometer. For the identification of the tracks of individual tigers and for the characterization of the ways that tigers move under different conditions, we repeatedly measured the impressions of the paws, the tigers' laying places, and the lengths of the tigers' paces and leaps.

The procedures for "reading" the information from the tracks that we used have been described in detail earlier (Matyushkin & Yudakov 1974), but the basic elements must also be noted here. We utilized the width of the impression of the big sole of the footpad (the "heel") (Abramov 1961b) as the most reliable indicator of sex and age differences among individuals. The most distinct tracks (under a dense canopy, on logs, on snow permeated with frozen water, on ice covered with a thin layer of powdery snow) were selected for measurement. The measurements were repeated a number of times, then the average magnitude was calculated. The repetition of the measurements is necessary, in order to eliminate possible errors caused by the condition of the substrate that had preserved the tracks. Even in the case of a homogeneous snow cover of insignificant depth, successive measurements of the width of the "heel" of only the front or only the rear paw of a single tiger varied in magnitude by approximately 0.5 cm. (for example, 8.5-9 or 11-11.5). If the sole of the pad is measured on a combined print, where the track of the rear paw is superimposed on the track of the front paw, the magnitude of the deviation increases to a maximum of 1 cm. In other words, the precision of the individual results, as a rule, does not exceed + 2-3 mm (or even + 5 mm).

Footprints can be substantially and reliably differentiated on a thin snow cover spread over ice, on ski tracks, and finally on loose (or friable) snow. In the case of a thin, crushable layer (approximately 1 cm deep), the tracks will always be smaller than when the entire paw sinks into the snow. Let us cite one example. On ice, which was covered with a ground-in layer of newly-fallen snow of several millimeters in thickness, the print of the front paw of a tigress was measured: total length 11.5, width 12, and the width of the "heel" 8.5 cm. The track of this same animal in the case of a snow depth of 3 cm. had a length of 13 cm., a width of 13.5 cm., and the width of the "heel" was 9 cm. Without additional evidence, it is only possible to consider a difference in the width of the heel pad that reaches or exceeds 1 cm as real (Matyushkin & Yudakov 1974).

While recording the measurements, we indicated precisely which track we measured: the front paw, the rear paw or an overlapping track. The prints of the front and rear paws of tigers are very similar in length (the front paw is sometimes a little longer) but there is a substantial difference in width. The powerful front paw (Fig. 11) leaves an almost circular imprint, while the rear paw leaves a relatively narrow, oblong print. The widths of the "heel" are also dissimilar, this difference being approximately 0.5-1 cm. in the case of females and young tigers, with a difference twice as large in the adult males. A double print produces the largest size [of two "summed" tracks, i.e., in practice, the front paw (and its "heels")]. Consequently, the impressions of the front paws should be taken as a basis for the elucidation of sexual and age characteristics of the tracks.

1All photographs were taken by the authors (except Fig. 20).

It is necessary to approach the identification of individual tigers based on their tracks with great caution, since two tracks with the same dimensions can, naturally, belong to different animals.

Figure 1.
Rear (on the left) and front right paws of a male tiger that is approximately four-years-old. Diagram of the measurement:
a) width of the paw, b) length of the paw, c) width of the "heel" (or big sole pad) of the paw

Table 1.
Dimensions of the Tracks of Amur Tigers of Known Sex and Age (cm)

Sex Agešššššššš Front Paw Length Front Paw Width Width of its "Heel" (i.e., the big sole pad) Conditions of Measurement
Male 18-20 years 15.5 15.5šššššššššššššššš 11.0šš on a corpse
Male 11-12 years -- ššš -- 10.5 on a corpse
Male about 10 years 14.0 17.5 11.5 on tracks and on the corpse
Male 6-7 years 13.5-14 14-14.5 10.5 tracks on snow
Male about 4 years 13.5-14 15.0 10.5 on a corpse
Male about 4 years 13.5 14.0 10.5 on a corpse
Male about 4 years -- -- 12.0 on a corpse
Male 3.7 years 12.0 šš 13.0 9.0 tracks on snow
Male 3.5 years -- -- 10-10.5 on damp sand
Male 1.1 years -- -- 9.0 on damp sand
Male 1.1 years -- -- 9.0 on damp sand
Male 4-5 months 8.5 9.5 6.5 on a corpse
Male 4-5 months 8.0 8.0 6.2 on a corpse
Male 4-5 months -- 8.5 6.5 on the living animal
Male about 3 months 6.5 7.0 5.5 on a corpse š
Female 16 years 12.0 12.5 9-9.5 tracks on snow
Female 6-7 years 11.5-12 12.5-13 8.5-9 tracks on snow
Female 6-7 years -- -- 9.5 on damp sand
Female 6 years -- -- 9.5 on damp sand
Female 4.5 years 12.0 12.5 8.2-8.5 tracks on snow
Female about 4 years -- -- 9.0 on a corpse
Female 3.5 years -- -- 9.0 on damp sand
Female 7-8 months -- -- 7.3 on the living animal
Female about 6 months -- -- 7.0 on tracks and on a corpse
Female 4-5 months -- -- 5.5 on the living animal

Note: This table is constructed mainly on the basis of published data (Matyushkin & Yudakov 1974; Bakhreev, Yudin & Nikolaev 1983); a dash indicates the absence of data.

According to data on the dimensions of the tracks of tigers in captivity, and also of tigers killed or shot in Primorskii Krai (Table 1), the heel pads of the front paws of adult male tigers and of tigresses (of the same age) clearly and reliably differ in size: the difference may reach 1-2 cm. and even more. Only with tracks of young animals (up to approximately the age of four years) is this difference harder to detect; sometimes, it is almost absent. "The greatest complication consists in the fact that three to 4 year old males, which have already started an independent life, can leave tracks similar to the tracks of adult females. Both their "heels" widths often fall into the 9-10 cm. group. Here, the determination of sex, and even more so, the answer to the question: " Are these different tigers?" requires an especially careful analysis. At the same time, animals in which the width of the heel pad exceeds 10 cm. (in practice, greater than or equal to 10.5 cm.) can, with certainty, be determined to be males. The great majority of measurements of the "heel" of males lie in the range of 10.5-11.5 cm.: the maximum value of this character is 13.5 cm. (in individuals markedly deviating from the norm). The corresponding range in tigresses is: 8.5-9.5 cm., with the upper limit to the variation at approximately 10 cm" (Matyushkin & Yudakov 1974, p. 15).

The tiger cubs differ from the mother in the size of their tracks only in the first winter, at an age of up to one year. In year-old males, the width of the heel pad can already reach 9 cm., being not less than 7 cm. in six-month-old cubs. During the census work, we measured the tracks of a family of tigers--a female with three cubs. The sizes of their "heels" were as follows: for the female, 8.5 cm. and for the cubs, 8 cm., 8 cm. and 7 cm. A tiger cub that was captured from this litter turned out to be a female of about 6-months in age, and it had a "heel" size of 7 cm. for the front paw and 6.2 cm. for the rear paw. It is even more difficult to recognize tiger cubs in their second year of life without special-purpose tracking. They differ from adults primarily in their behavior: they very often go into leaps and frequently lie down. In addition, as L. G. Kaplanov (1948) had already noted, tiger cubs have a shorter stride, and, when following the tigress through deep snow, they do not step into the series of holes laid down by her.

"Laying places in the snow can also serve for the discrimination of individual tigers. Thus, the length of the laying place in the "Sphinx" position (with the hind legs folded back sideways) of large males is close to 2 m.; in the case of tigresses, it fluctuates in the range of 1.5-1.7 m. Since the dimensions measured here are considerably larger than those for paw prints, the influence of measurement errors on the conclusions of the observer is substantially reduced"(Matyushkin & Yudakov 1974, p. 17).

The tigers on which we conducted regular observations either had identical "heel" sizes (for the two females) or were similar in size (for the three males). In the first case, they were both 9.5 cm. in size, while, in the case of the males, they were 10.5 cm., 11.5 cm. and 12.0 cm. in size.

The sex of the animals was determined by a combination of traits, namely: the presence of a litter, the sizes of the tracks, the frequency of "scrapes" and of approaches to trees and rocks with the intention of marking them. Winter tracking showed that the frequency of marking approaches by females was substantially less than the number of marking approaches by males: Likewise, "scrapes", which are characteristic of males, were not seen at all with females, or else only as rare observations. Occasional encounters with tigers, of course, did not allow the possibility of using these characteristics: they were only detected during the course of tracking. It is practically impossible to determine the sex of tigers by means of urine stains: they are similar in males and females.

The tigresses that were under observation also differed according to their movements relative to each other--they lived in different territories, and their routes during the period of the study did not cross each other even once. The size differences among the tracks of the males always allowed us to distinguish them with certainty. In such situations, the attribution of a track to one or another individual animal was determined by a long, uninterrupted period of tracking. The differentiation of the individual males according to their tracks was facilitated by the individual features of their behavior and also by the sequence of our observations of these tigers. The observations of the male with a "heel" of 10.5 cm were begun in February, 1971. The tracks of another tiger (with a "heel" of 11.5 cm) appeared on the individual territory of the first tiger in November, 1972. The main travel routes of the first tiger were already known to us by approximately this time. During the course of tracking the second tiger, several differences in their behavior were revealed. In January, 1973, the second tiger died in a fight with a third tiger which we had not previously encountered (with a "heel" of 12 cm), whose path was followed mainly after the fight. This new male differed from the first in the very same characteristics as those of the paths of the tigresses: their individual territories were in contact with each other to only an insignificant degree.

During the tracking, we measured, photographed, mapped, and described (with reference to time and to the territory) everything that the tigers did. On their routes, we recorded stops, changes of pace (or "gait", Fig. 2), and the direction of movement. Upon encountering laying places of various types, we determined (to the extent possible) the length of the tiger's stay there, and the nature of the behavior of the animals at the laying place. We estimated the frequency of laying sites as they depended on the topography [slope, upgrade (rising slope), "flat" sectors of the route] and on the depth of the snow cover. When describing laying places where a tiger remained for a long time, we investigated the tiger's approach to them, the sites where they were located--in shelters (niches in rocks, under ledges) or without special concealment, the accessibility of such sites to solar radiation, the availability of bedding, the protection from precipitation, from wind, and from concealed approaches by possible enemies of the tiger. We noted urination sites, excrement, "scrapes", and scratches on trees. We described the behavior of the tigers upon encounters with people or with moving vehicles, and their reactions to the tracks and paths made by people and by other animals in different types of forest structure, to machinery that was not in use, and to trapping gear [leg-traps, hunting nets].

Figure 2. Gaits of the Amur Tiger (after Matyushkin & Yudakov, 1974):

a) Tiger tracks during unhurried walking on a thin snow layer (in each pair of prints the front paw print is behind the rear one's)

b) Tiger tracks during unhurried walking on snow of a depth greater than 10 cm. (the footprints of the front and rear paws are combined)

c) Tiger tracks during a trot [the furrows from the "tail ends" of the prints are elongated]

d) Tiger tracks from a spring

When describing the hunts of the tigers, we paid attention to the methods of concealment (lying in ambush for prey, pursuit of the prey by tracking it, encountering en route animals that are feeding or lying down), the distance at which the prey was discovered, the duration of the chase, and the tiger's maneuvers upon approach to the prey.š We measured "springs" by the tiger and the number and lengths of the leaps made by the predator or the prey.š We evaluated the original site of the attack relative to the topography (whether the prey was found up-slope or down-slope).š We weighed the factors favoring or preventing a successful attack (the condition of the snow cover, the degree to which the area was "cluttered" up with debris, etc.).š When we found dead prey we determined (to the degree possible) the method by which it had been killed; we noted whether it had been eaten on the spot or whether it had been dragged.š The approximate amount of time spent by the tiger around its prey was established based on the amount of meat eaten, the presence and amount of excrement, of urination sites, of material thrown about, the number of laying places near the site of the meal, and also by the degree to which the prey was frozen through.š However, it was only possible to achieve a sufficiently exact time estimate in those cases where either beginning or the end of a snowfall, the time of formation of a thin crust of ice over snow, or thaws served as reference points.š During the determination of the daily travel of the animals, we also depended on both these same reference points and also on encounters with the tigers themselves (or their fresh tracks) somewhere at a reliably determined time.š In the absence of such "reporting points", it was necessary to estimate the duration of daily travel by using other characteristics, for example, the number of long stays in the laying places, but the precision of such estimates is not high.
Information about the data collected with an enumeration of all tracking episodes (complete sections) and a short description of the data produced for each separate instance of tracking is presented in Table 2.

Table 2.
Summary Data for Tiger Tracking in the Long-Term Study Area for the Entire Period of Observations (1971-1973).

Sex of Tiger Width of the "heel" of the front paw (cm.) Year of Observation Tracking Duration Date of Discovery of the Tracks and their Freshness upon Discovery Distance of Uninterrupted Tracking (km.) Number of Days Spent by the Tiger on this Route Number of Long Rest Stops Prey Found
Male 10 1971 Jan. 18-22; 2,3 Feb. Jan. 18; tiger passed on Jan. 17 after 17:00 hrs 56 unclear 5 yearling Manchurian red deer ("sayok"); adult boar (male)
Male 10.5 1971 Feb. 14-18 Feb. 14; 2-3 days old 31.7 Unclear 3 female Himalayan bear with a cub
Female with 2 cubs 9.5 1971 Feb. 15-18; Feb. 24 Feb. 15;more than 2 days old 37.8 Unclear 3 and 2 (lairs of the cubs) a piglet and the bears mentioned above
Male 10.5 1971 Feb. 23, 25,27; March 2,3,7,8,11,13 Feb. 23; passed on that day at 10:00-11:00 hrs 47.5 Unclear 5 Manchurian red deer (female)
Female 9.5 1971 March 14-17, March 19-22 March 12; passed during the night of March 11-12 34.6 Not less than 4 5 a dog; a musk deer
Female 9.5 1971 March 14-17, 22-24, 31; April 1-4 March 14; more than 2 days old 78.1 Unclear 7 yearling Manchurian red deer ("sayok")
Female with 2 cubs 9.5 1971 March 21,22,26,31; April 1-3 March 21; passed on the night of March 20-21 26.9 Unclear 4 and 4 (lairs of the cubs) a piglet
Female 9.5 1971 Nov. 19,20,22,23,25-27. Nov. 15; passed on that day 71.4 Unclear 3 a dog
Female with 2 cubs 9.5 1971 Nov. 26 and 28. Nov. 26; more than 2 days old 12.1 Unclear 1 a piglet
Male 10.5 1971 Nov. 20 and 22 Nov. 20; 2 days old 16.9 Less than 24 hrs 1 none
Male 10.5 1971 December 1-2 Dec. 1; not more than 2 days old 26.2 About 24 hrs None none
Female 9.5 1972 January 26-29 Jan. 26;passed on that day towards morning 43.3 Not less than 4 7 a piglet
Male 10.5 1972 Jan. 30-31; Feb. 1-5 Jan. 29; more than 2 days old 43.3 Unclear 7 a male Manchurian deer (shpil'nik")
Male 10.5 1972 Feb. 4,6,8-12 Encounter with the tiger on Jan. 31 at 19:00 hrs 66.9 Unclear 11 a piglet
Female 9.5 1972 Feb. 14 Feb. 11; less than 24 hrs 17.2 Unclear 1 none
Male 10.5 1972 Feb. 14 Feb. 14; 2 days old 3.8 Unclear None none
Male 10.5 1972 Feb. 25-27 Feb. 24;more than 2 days old 26.5 Unclear 4 none
Female 9.5 1972 Feb. 25-29; March 3-4 Feb. 25; more than 2 days old 44.7 Unclear Not less than 3 a piglet
Female 9.5 1972 Feb. 29; March 1-11, 15 Feb. 29; passed towards the morning of Feb. 29 97.7 About 8.5 10 a piglet (male); a pig (female);
a yearlingManchurian red deer ("sayok"); roe deer (male), a piglet (male)-4-9 months old
Male 10.5 1972 March 4-14,16-18 March 4; passed on Feb. 28 152.4 19-20 20 a piglet; Manchurian deer (a male and a female)
Male 11.5 1972 Nov. 25-30 Nov. 25; passed on Nov. 24 85.5 2.5-3 9 none
Female 9.5 1972 Nov. 28-29 Nov. 26; passed on the night of Nov. 25-26 9.8 Less than 24 hrs 2 none
Female with 2 cubs -- 1972 Dec. 26 Dec. 26; passed on Dec. 17 4.7 Stayed with the prey for several days 5 a Manchurian deer ("shpil'nik")
Male 11.5 1972-1973 Dec. 19-21,24,25,27; Jan. 8-10,17,21,22 Dec. 19; passed on Dec. 17 156 Not less than 15 days 22 5 piglets
Male 11.5 1972 Dec. 22-23 Dec. 12;passed on the night of Dec. 11-12 18.2 Unclear 2 none
Male 9.5 1973 Jan. 12-13 Jan. 12; passed during the morning of Jan. 12 14.2 Somewhat over 24 hrs 2 a piglet
Male 11.5 1973 Jan. 14,15,17,21-25 Jan. 12; passed on the night of Jan. 11-12 34 Unclear (killed in a fight) 7 over a distance of 5-7 km none
Male 10.5 1973 Jan. 11-15,17,21-27 Jan. 11; passed on Jan. 10-11 59.2 About 2 days 8 a piglet
Male 12.0 1973 Jan. 25 and 29 Jan. 24; passed from Jan. 11-12 11.7 Unclear (a fight) 2 (after the fight) none
Female 9.5 1973 March 2-6 March 2; passed from Feb. 24-25 50.9 10-11 9 a roe deer (probably already dead), a piglet, a boar (male)
Male 10.5 1973 March 23, 24 March 23; passed between March 17 and March 21 23.2 Unclear 2 a yearling Manchurian red deer ("sayok")
Male 10.5 1973 March 28,29-31; April 6 Encounter with the tiger on March 28 at 18:40 hrs 23 Unclear Not recorded a piglet
Male 10.5 1973 April 7,9-13,15,18,19 March 28; passed on that same day 21 Unclear Not recorded none
A female with a male tiger 9.5 1973 Nov. 21,22 Nov. 21; both tigers passed after Nov. 18 8.5 Unclear None none

Copyright ¿ A. G. Yudakov,I. G. Nikolaev

Copyright ¿ K. Lofdahl, A. Shevlakov, 2004 (English translation)