Behavior of Varanus Griseus During Encounters with Conspecifics
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1997 Asiatic Herpetological Research Vol. 7, pp. 108-130 Behavior of Varanus griseus during Encounters with Conspecif ics ALEXEY YU.TSELLARIUS AND ELENA YU.TSELLARIUS Program VARAN, Dept. Herpetology, Zoological Institute. 199034. St. Petersburg. Russia - of Abstract. In 1990-1993 in the western region of the deserts of Kyzylkum (Uzbekistan), constant observations of various a group of desert monitors in natural conditions were conducted. Described are manifestations emotional states of monitors, and common types of monitor interaction. Given are detailed descriptions of the course of contacts between the animals, illustrated by photographs. Fights were rarely noted and only between of and not from a unfamiliar lizards. It is proposed that ritual combat arises from displays dominance is varied and not Data ntualization of the fight. The behavior of monitors during contacts highly stereotypical. from observations attests to the existence of a complex, mammal-like social structure in the population. Considered are probable mechanisms of intraspecific communication of monitor lizards. Key words: social behavior, social relations. Reptilia. Sauria, Varanus griseus Introduction Behavior of animals during intraspecific contacts is usually considered as a succession of behavioral acts, In the article at hand we have made an to attempt but not as a social interaction directed at the mainte- reveal the communicational function of common nance of long-term interrelations within a socium. behavioral acts of desert monitor. We have made also The analysis of behavior is reduced to statistical anal- an attempt to describe some types of interactions ysis of the sequence of the behavioral acts of contac- between monitors and the role of these interactions in tants. Generally, the task of the analysis is limited to social organization of population. We will not touch discovery of the most probable response of a lizard to behavior connected with courtship and mating upon the acts of another lizard. In analysis one seldom in the article. present allows for the circumstances, under which the interac- for the of endan- In 1989. when a program study tion took place. The history of interrelations of con- gered species of reptiles was developed by us, the tactants, as a rule, is not taken into account at all. principal emphasis was put upon their ecology. Actually, the social interaction is considered as a behavior of When we stumbled onto the fact, that the closed system with internal self-regulation, indepen- the monitor lizard is much more complex than was dent of the structure of the socium. imagined, we no longer had the opportunity to alter Viability of the population (the ability for bal- the program of study. Hence, the gathering of etio- anced reproduction in particular) is to a considerable material had to be conducted at the same time logical extent determined by its social structure. The social as the primary tasks. Although we are aware of the structure of many species is rather impressed by envi- of our data and the necessarily sche- incompleteness ronmental conditions and the reptiles are not an matic and fragmentary nature of our description, we exception (Panov, Zykova, 1985; Poly nova, Panyush- do not consider its publication to be in vain. This kin 1982; Polynova, 1990; Stamps; 1977). A social issue has not only theoretical but practical signifi- response of population to environmental changes is cance since desert monitor populations arouse serious often species-specific (Polynova, 1990) and is not apprehension in many regions of Middle Asia necessarily adaptive (Plyusnin, 1990). Peculiarities of (Darevsky,Orlov 1988. Khodzhaev 1989) response of socium to the external influences are to the ele- There exists a vast literature dedicated determined for the most part by two closely interde- lizards the of mentary behavioral acts of (see survey pendent, species-specific systems of animal activity: behavior of some Carpenter. Ferguson 1977). The a) a production of the signals which carry information species of monitor lizards has also been described in about the animal and its circumstances; b) a percep- some detail (Auffenberg 1981a; 1981b: 1983: 1988; tion, processing and analysis of these signals in con- Carter; 1990; Davis et al. 1986; Deraniyagala 1958; junction with others external and internal irritants. But Gaulke 1989; Horn et al. 1994; Mertens: 1946). The principles of organization of these processes may in the most of herpetological papers the social motives be termed as a "language" and a "mentality" of a spe- and purposes of behavioral acts are not examined. cies. This issue is closely linked to the problem of 1997 Asiatic Herpetological Research Vol. 7, p. 109 management of populations and demands careful monitor lizard was specially caught, usually in the study. morning hours. In the evening of that same day we attempted to establish from tracks the site where The of Studies Region another monitor would spend the night. At dusk we The studies were conducted in the western area of the released the monitor captured earlier into a nearby sand deserts of Kyzylkum. Uzbekistan. The coordi- burrow. In the morning, as the monitors emerged nates of our permanent camp were 40° 40' N and 62° from their overnight shelters, encounter was inevita- 08' E. The landscape in this region is typical of the ble. It was only possible to perform these operations -- Kyzylkum sandy ridges, bushy undergrowths from time to time so as not to disturb the lizards and the (mainly Haloxylon persiewn, and Calligonum sp.), disrupt normal course of their lives. In some and sparse grass (Care.x physodes predominates) (Fig. instances discussed in this article, data from tracking 1 ). In the region of studies there is a rather high abun- was also used when it was possible to precisely and dance of rodents, for the most part Rhombomys opi- fully reconstruct the course of events from the tracks. mus and Spermophylopsis leptodactylus. Both During observations from hiding, detailed steno- inhabited and abandoned colonies of Rh. opiums — graphic notes were taken which were deciphered with their complex system of underground passages immediately after observations were concluded. and location not farther than 150-200 meters from one Some of the encounters were photographed (from 5 to -- another serve the monitors as refuges and hunting 16 frames per encounter). Unfortunately, a lack of grounds. means prevented us from employing photographic documentation to the extent that was necessary. In all. Materials and Methods we observed 37 instances of contact between males, 8 instances of contact between females, and 21 Observations were conducted from 1990 to 1993 for instances of contact between the sexes. periods of four to seven months annually. In all, observations were made for a duration of more than Results 20 months. In the beginning of April, the period in which monitor lizards come out of hibernation, they The Spatial Structure of the Population and were measured, marked, and caught, weighed, Annual of - Dynamics Activity released at the site of their capture usually in the Data pertaining to the spatial structure of the popula- course of a few hours after being caught. A special tion is currently being readied for publication in a sep- mark permitted us to identify the animals by their arate article. Here, however, it is only necessary to tracks (Tsellarius and Cherlin, 1991 ). Henceforth, for address a few words to this issue. The number of the greater part of the season of monitor lizard activity monitor lizards in the of studies consisted on we conducted continuous observations of the animals region — the average of four adult individuals per square kilo- following their tracks and observing them visually meter. The monitors were, however, distributed over from camouflaged holes situated in the places where the space unevenly: areas of high concentration alter- the appearance of monitors was most probable. In nating with thinly populated areas. Areas in which order to determine age, we amputated the last phalanx populations were more densely concentrated (settle- from one of the fingers of a number of the monitor liz- ments) measure nearly 100-150 hectares. The dis- ards. The specimen was processed by E M. Smirina tance between the centers of neighboring settlements (Moscow) to whom we owe our sincere gratitude. ranges from 3-5 kilometers. Each settlement is The region of operations was regularly inspected and formed from a group of adult settled individuals con- all points at which a tracks of the marked animals was sisting of five to six males of various ages and three to apparent were plotted on a chart. As a result, we have four females. In each of two settlements which were at our disposal data on age, the location of home under constant surveillance, only one female took ranges, and the nature of the interrelations between part in reproduction. The rest of the females were not the majority of the mature individuals settled in the impregnated over the entire period of observations region of operations. although they were in fact courted by the males. The Indirect exchange of information predominates in home ranges of all of the animals in a settlement the population (Tsellarius and Men'shikov, 1994). almost fully overlap each other. In the sparsely settled The monitor lizards comparatively rarely enter into areas between settlements, home ranges may, to a direct contacts. A possibility of observations of con- varying degree, either overlap or be located at certain tacts is all the more rare. Therefore, in order to gather distance from one another. The home ranges of set- sufficient data, we provoked contacts. To this end. the Asiatic Research 1997 Vol. 7, p. 110 Herpetological is in motion. When the monitor examines tied animals range from 30 to 200 hectares in size. any object burrow From time to time, each of the males makes brief, dis- with its tongue (e.g.