Effect of solar eclipse on the behavior of a captive group of chimpanzees (Pan troglodytes).код для вставкиСкачать
American Journal of Primatology 11:367-373 (1986) Effect of Solar Eclipse on the Behavior of a Captive Group of Chimpanzees (Pan troglodytes) JANE E. BRANCH' AND DEBORAH A. GUST1r2 'Yerkes Regional Primate Research Center, Emory University, and 'School of Psychology, Georgia Institute of Technology, Atlanta A captive group of chimpanzees, housed in a n outdoor compound at the Yerkes Regional Primate Research Center, was observed during the annular solar eclipse of May 30, 1984. The behavior of each animal was recorded using a n instantaneous scan-sampling technique (Altmann: Behaviour 49:227-265, 1974). Beginning 2 days prior to the eclipse and continuing through the day following the eclipse, data were collected from 1100 to 1300 hours daily. At 1214 hours on the day of the eclipse, when the sky began to darken and the temperature began to decrease, solitary females and females with infants moved to the top of a climbing structure. As the eclipse progressed, additional chimpanzees began to congregate on the climbing structure and to orient their bodies in the direction of the sun and moon. At 1223 hours, during the period of maximum eclipse, the animals continued to orient their bodies toward the sun and moon and to turn their faces upward. One juvenile stood upright and gestured in the direction of the sun and moon. Sunlight began to increase a t 1225 hours, and as it became brighter, the animals began to descend from the climbing structure. The behaviors exhibited by the group during the period of maximum eclipse were not observed prior to or following the eclipse nor as darkness approached a t normal, daily sunset. These data indicate that a solar eclipse, a rare and uncommon environmental event, can influence and modulate the behavior of chimpanzees. Key words: apes, sun, environmental phenomenon INTRODUCTION On May 30, 1984, the Atlanta area experienced a n annular solar eclipse. Approximately 99.7%of the sun was blocked out by the moon, leaving a ring of light around its periphery. The path of the eclipse extended from Louisiana to Virginia. The event began at 1150 hours, and by 1223 hours the eclipse had reached annularity, its nearest approach to totality (maximum eclipse). At annularity, the moon appeared as a black spot between the earth and sun, surrounded by a ring of light. The previous solar eclipse observable in Atlanta occurred on May 28, 1900, and the next total eclipse visible from Atlanta is predicted to occur on May 11, 2078. Received March 12,1986; revision accepted June 22, 1986. Address reprint requests to Deborah A. Gust, Yerkes Regional Primate Research Center, Emory University, Atlanta, GA 30322. 0 1986 Alan R. Liss, Inc. Solitary Sitting Sitting, eating, drinking Self-grooming Playing alone Lying, eating, drinking Standing Standing, eating, drinking Looking Rocking Other Interactive Approaching Touching Reacting to Taking object from Grooming Sitting near Playing Chasing Mother-infant Other Displace Hit Other Aggressive Other directed Nondirected Vocalizations Climbing Walking Running Rolling Locomotion Sitting Lying Standing Walking Running Other Postural TABLE I. Behavior Categories Used for Instantaneous Scan Samples of Chimpanzees Pulling object Pushing object Examining object Other Manipulative Mounting Inspecting genitals Courting Touching Sexual - o u t of view Solar Eclipse and Chimpanzee Behavior I 369 Studies of animal behavior during a solar eclipse have been relatively sparse. Within the last few years, reports have described the phenomenon in, for example, waterfowl [Loftin, 19711, freshwater fish [Pandey & Shukla, 19821, songbirds [Elliot & Elliot, 19741, egrets [Kumar, 19811, and rodents [Advani, 19811, but few have described the reactions of nonhuman primates to a solar eclipse. Dixit et a1  and Mukherjee  studied rhesus monkeys, and Mohnot  studied Hanuman langurs during the 1980 solar eclipse in India. Mukherjee  reported noticeable behavioral differences in rhesus monkeys, and Mohnot [ 19811 noted few behavioral changes in langurs during the eclipse. The present report describes changes in the behavior of a group of chimpanzees during a solar eclipse in Georgia. The study capitalized on the location of a research site, which was within the path of the annular solar eclipse, thereby providing the opportunity for a n unusual experiment involving the behavior of the chimpanzees. The objective was to observe, record, and characterize the behavior of a group of common chimpanzees housed in a n outdoor compound before, during, and after the eclipse to determine whether the animals would exhibit discernible changes in behavior during the period of the eclipse. METHODS Sixteen common chimpanzees (Pun trogladytes) of both sexes served as subjects for the present study. Subjects were identified as infants (n = 41, juveniles (n = 31, adult females (n = 8), and adult male (n = 1).All were contained as a social group within a 23.77 x 29.26-m outdoor compound a t the Field Station of the Yerkes Regional Primate Research Center. The perimeter of the compound comprised openmesh fencing 2.1 m high and 4.77 m of sheet metal above the fencing. The compound was not covered, and its location provided a direct, unobscured view of the sun and moon during the eclipse. During 2-hour periods on 4 consecutive days, the subjects were observed from an elevated platform overlooking the compound, and the behavior of each animal was recorded on a behavioral checksheet during successive 10-minute scan-sampling periods (Table I). Weather conditions were characterized and recorded for each scan sample. Data were collected from 1100 to 1300 hours daily beginning 2 days before the eclipse and ending 1 day after the eclipse, yielding a total of 45 scan samples in addition to 3 sample periods during the actual eclipse when only a videotape record was obtained. Prior to data analysis, interobserver reliability was assessed using the checksheets, and i t was found that the two observers were in agreement on 91% of the scans. On the day of the eclipse, the vocalizations and behavior of the group were also recorded and videotaped during the sampling periods. Unfortunately, behaviors that changed a t the onset of and throughout the eclipse (e.g., orientation, position on the climbing structure, gestures) were not included on the checksheets; thus, statistical analyses were not possible. In addition to the 4-day observation period, the animals were observed during normal sunset to determine whether behavior patterns exhibited a t the end of the day were similar to those noted during the eclipse. Using behavioral checksheets, six scan samples were obtained during a 1-hour period preceding sunset. RESULTS Subjects were observed on the climbing structure on 2 days preceding and 1day following the eclipse. In contrast to behaviors exhibited during the eclipse, the chimpanzees that were on the climbing structure, on the days preceding and following the eclipse, oriented toward other animals and objects within the compound a t or below eye level rather than toward the sky. No more than four individuals were Fig. 1. Sequential frames of videotape showing the behavioral activities of a group of chimpanzees prior to, during, and following an annular solar eclipse, Changes in level of ambient illumination associated with the eclipse precluded clearer video-recordings of the subjects. Descriptions of successive frames are included in the text. Solar Eclipse and Chimpanzee Behavior / 371 observed on the climbing structure a t any one time, and no animal remained on the structure for more than 20 minutes. At 1214 hours on the day of the eclipse, as the sky began to darken and the temperature began to decrease, individuals in the group exhibited atypical behaviors. Solitary females and females with infants moved to the climbing structure and ascended to the topmost positions (Fig. 1A). At 1216 hours, other animals moved to the climbing structure, ascended, and congregated near the top, sitting and standing in close proximity to one another and orienting their bodies toward the sun and moon. At 1217 hours, individuals continued to move to the climbing structure and to face toward the direction of the sun and moon. At 1220 hours, all animals on the structure were orienting toward the direction of the darkened sun. At 1222 hours, one chimpanzee momentarily stood upright on top of the climbing structure (Fig. lB, arrow). In addition, some animals turned toward the direction of birds heard singing outside the compound, then resumed their sun-orienting postures (Fig. 1C). At 1223 hours, the onset of totality, all animals on the structure oriented toward the sun and moon with their faces turned upward, and one animal gestured as if pointing in the direction of the sun and moon (Fig. 1D). During this time, the adult male and three adult females rested quietly along the shaded periphery of the compound. Sunlight began to increase a t 1225 hours, but the animals on the climbing structure continued to orient toward the sun and moon (Fig. 1E). Shortly, thereafter, two animals climbed to a lower portion of the structure, and some began to shift their gaze away from the sun and moon (Fig. 1F).Two animals, previously limited to lower positions on the structure, ascended to the top once those positions were vacated and then oriented toward the sun and moon (Fig. 1G); 2 minutes later, they descended from the highest point. At 1235 hours, as brightness increased, more animals descended from the climbing structure, and two females at the top of the structure continued to focus in the direction of the sun and moon (Fig. 1H). One adult female and a juvenile male, previously resting along the periphery of the compound, moved toward the center of the compound. Figure 1 H (arrow) shows an adult female holding a n infant while a second animal places her hand on the female’s shoulder. Throughout the eclipse, all animals remained in the open compound, and none entered the indoor living areas. It was 1245 hours before the group descended from the structure and exhibited behaviors typical of those observed prior to the eclipse (Fig. 11). When the group was studied, subsequently, during normal sunset to compare the effect of diminishing light a t sunset and at the onset of the eclipse, the animals did not group together on the climbing structure as darkness approached. At 1710 hours (50 minutes prior to sunset), half the animals were walking around the compound, and half were sitting alone at various positions. At 1720 hours, two juveniles were sitting on the climbing structure and seven females were on the ground, three in close proximity to each other and four sitting alone. The remaining animals were in the indoor living area and out of view. By 1750 hours, all animals were in the indoor areas, and at 1800 hours (sunset), two animals were seen sitting near the entrance to the indoor areas. DISCUSSION Several investigators [e.g., Goodall, 1968; Kano, 1971; Nishida, 1970; Sugiyama, 19681 have provided considerable data on typical chimpanzee behavior and ecology, but there are few reports on the behavioral reactions of chimpanzees to infrequent or aperiodic natural events. Goodall [1968, 19711 and Bygott  noted an apparent behavioral reaction by chimpanzees to weather conditions. They reported that 372 I Branch and Gust the animals exhibited a type of “rain-dance” during very heavy rainfall. The behavior was typically initiated by one adult male and included irregular “pant hoot” vocalizations accompanied by charging while breaking and dragging branches, The “rain-dance” ceased when the rainfall began to subside. As in the case of the “rain-dance” phenomenon, most of the behaviors exhibited during the period of annularity in the present study were not seen prior to or following the eclipse, nor during normal sunset. The most salient behavior noted during the eclipse was grouping in close proximity a t a n elevated level above the compound floor and orienting toward the sun and moon. Mukherjee [ 19841 reported that a group of rhesus monkeys, which traveled and behaved as a unit under normal conditions, divided into subgroups and bedded down during maximum darkness of a n eclipse. Similar to the subjects of the present study, the monkeys resumed typical behavior patterns a t the end of the eclipse. The chimpanzees’ atypical behavior during the annular eclipse in the present study did not correspond to previous reports of nonhuman primates during a solar eclipse [eg, Dixit et al, 1981; Mukherjee, 19841; however, direct comparisons are difficult given the different living environments, weather conditions, and degrees of eclipse. The present study documents the effects of a salient environmental event on the normal, daily activity patterns of a social group of chimpanzees living in a seminatural environment. Behavioral changes have been reported for several other species, but there have been no previous reports of the phenomenon in chimpanzees. Wojtusiak and Majlert 119761 reported that the behavior of several species can be affected by a solar eclipse; thus, it should not be surprising that a n eclipse can produce marked changes in the behavioral activity patterns of chimpanzees in a seminatural environment. The behaviors observed in the present study were undoubtedly not characteristic of the group under normal conditions nor during sunset on normal days. Unfortunately, the low frequency of occurrence of a total solar eclipse in any given area makes subsequent studies with a group of subjects very difficult. The present study can serve as a stimulus, however, for planning additional studies in conjunction with the next predicted solar eclipse. CONCLUSIONS 1. During the annular solar eclipse of May 30, 1984, a group of chimpanzees housed in a large outdoor compound exhibited behaviors that were not observed during scan samples taken before and after the eclipse. 2. The chimpanzees gathered in close proximity on a climbing structure situated in the middle of the compound and oriented their bodies toward the direction of the sun and moon during the eclipse. 3. Similar behaviors were not observed during a typical, daily sunset. ACKNOWLEDGMENTS The authors thank Dr. L.D. Byrd and Ms. P.M. Plant for comments during the preparation of the manuscript and Dr. T.L. Maple and Dr. R.B. Swenson for help in arranging to conduct the study. This research was supported, in part, by U.S. Public Health Service grants DA-01161 and RR-00165 (Division of Research Resources, NIH) to the Yerkes Regional Primate Research Center. The Yerkes Center is fully accredited by the American Association for Accreditation of Laboratory Animal Care. REFERENCES Advani, R. Some observations on behaviour of rodents during solar eclipse. JOURNAL OF THE BOMBAY NATURAL HISTORY SOCIETY 78:590-591,1981. Altmann, J. Observational study of behavior: Sampling methods. BEHAVIOUR 49:227265,1974. Bygott, J.D. Agonistic behavior, dominance, Solar Eclipse and Chimpanzee Behavior I 373 and social structure in wild chimpanzees of the Gombe National Park, pp 405-427 in THE GREAT APES. D.A. Hamburg; E.R. McCown, eds. Menlo Park, CA, N Benjamidcummings, 1979. Dixit, V.R.; Singh, R.; Chandel, N.K.; Sinha, S.N. 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