L11-Lindauer_71 - Lindauer, M. 1971. Special problems...

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Unformatted text preview: Lindauer, M. 1971. Special problems concerning solar orientation in relation to the bees' dance. ln. Communication Among Social Bees. Harvard University 5 Press. Special Problems Concerning Solar Orientation in Relation to the Bees’ Dance IN THE LAST CHAPTER we MET with some of the problems involved in solar orientation. During recent years we have directional indication in dancing, their flights toward the goal must first have been oriented with respect to the sun. Some experiments conducted years ago by Wolf (1926, 1927) gave some hints that this may be the case. The bees were trained to find a feeding table 150 meters north of the hive, and after a while this feeding table, together with the bees sitting on it, was carried to a new location a few meters south of the hive. When the bees were now released from the feeding table, they did not return directly to the hive, but first flew 150 meters southward, as they were used to doing in their normal return flight, and there searched eagerly for the hive (Fig. 60). Only after long searching I]? if Feeding Piece sze s Q 3 I //J? 4" «xxx. l I / I ‘\ I ’ “t ‘ i \ l I! ‘ \ l x i \ l j l/ t, I l // / i l l // f 1, l I ” ’ t l / . 4 l ,f” r/ l l t / I ‘ l / I \\ l/ g x i .4- G \. ~ ._ .. . m...» rue-v0" l i K .__ "ys‘ugf‘ 1 .. i l t l t t l k . 5, l t l \ l \ I \ x I \l \ +l // r'“; i 11:“, {‘- A/ w—l/ F IO. 60. A group of collector bees was captured upon the feeding table they were visiting, the table and bees together were displaced to a point on another side of the hive, and the bees were released. Now they did not fly directly back to the hive, but at first How in the accustomed southerly direction, and after 150 meters began an obstinate search for the hive. An extraterrestrial fixation point—not landmarks of the sur-' rounding terrain—must have served for their orientation in determining the direction for the home flight. (After VVolF, 1927.) 1 i3 i l r .i COimcsicATION Amosc Socw. BEES flights did they find their way back to the hive, which was still standing in its original location. They responded in an analogous way when the table was moved to a point west or east of the hive. This means that these bees had oriented themselves on their home flight according to some distant reference point, probably one in the sky. We can demonstrate this orientation with respect to the sky still more strikingly in the following experiment. A bee colony is transferred to an unknown territory, and a group of collector bees, individually marked with spots of color, is fed at a point about 180 meters south of the hive. This is repeated for several days; the bees learn that there is food to be had south oféhe have. Overnight, the colony is then displaced into a new, also unknown territory. There, four feeding tables are installed for the bees to choose from: 180 meters to the south, west, north, and east. Each bee that now arrives at one of the tables is promptly captured by an observer, so that it is unable to inform and alert others in the hive. This means that each collector bee must start her flight on her own initiative, choosing her own direction, to search for a food source. No familiar landmark points the direction in which they were formerly trained; only the dome of the sky, crowned by the sun, stands unaltered above the experimental terrain. The trained group of eol~ lectors do find their way, unambiguously, to the table in the south. Only the sun can be their guide (yon Frisch and Lindauer, 1954). It still remained to be discovered, however, how the bees used their solar compass. Did they keep in mind on each flight, on every training day, which point of the sky was occupied by the sun? And did they—after transposition-— memorize the angle between sun and feeding table for each time of the day? Their perfect time sense would enable U4 SPECIAL PROBLEMS (josctaslsc SOLAR ORIENTATION them to do so (Beling, 1929, Renner, 1957). Or are they even able to compute the movement of the sun for purposes of their solar orientation? The marathon dancers, which we mentioned on page 95, convinced us that this latter ability exists. Our experiment of diSplacing the hive, in a modified form, was made to furnish new evidence for this fact. Again a hive was placed in unknown territory, but this time the group of collectors was fed south of the hive only morning. The flight hole was opened at 7 a.m., and four feeding tables were placed at the four points of the com— pass. We counted only those feeding-table visitors that arrived before noon. Had the bees remembered the abso- lute angle between the sun and the direction to the feeding place, one would expect them to fly in the wrong direction —in this case eastward, since on the preceding afternoon the feeding table had stood to the left of the sun, and now in the morning the feeding table in the east occupied the same position with reference to the sun. But again, the col- lector bees unanimously flew south, thus furnishing addiw tional proof that they can somehow compensate for the movement of the sun, by computation (von Frisch and Lindauer, 1954-). We may now ask the question: how would the bees react when presented with a sun whose position in the sky has been shifted, so that it indicates the wrong direction? During a stay in Ceylon, I trained the bees to feed at noon at a station 150 meters to the north. This was done in April, when the sun was moving northward, and the training was limited to a few minutes at noontime, when the sun stood U5 (ZOMML‘NICA'I‘ION AMONG 80cm. BEES exactly in the north, that is to say, in the direction of the feeding place. After a week of training in this way, I took the bees overnight by plane to Poona, India. Poona isjust far enough to the north that the noonday sun at the end of April stood exactly as far to the south of the zenith as in Ceylon it was to the north (Fig. 61). Shortly before noon, I Opened the flight entrance; four feeding tables were available again, at north, east, south, and west. The bees now flew to the south instead of to the north; in other words, they oriented themselves according to the sun alone, and, since it had been shifted, the bees necessarily mistook south for north (Lindauer, 1957). Thus they demonstrated that the sun was their only compass and that they can use it correctly only in that part of the world where they have been born. A new question immediately arises, however: is this ability of the bees to orient themselves according to the sun innate, or must the bees [earn the solar orientation ap- propriate to their geographic location? One might suppose, furthermore, that the bees become imprinted, during their preliminary exercise flights (the “ Vors‘pz'el”), with the direc- tion of movement of the sun and its angular velocity across spheres, therefore populations living in diflerent hemispheres must compute for solar movement in opposite directions: in the north, clockwise, and in the south, counterclockwise. In addition, the course of the sun changes with the seasons. An especially complicated situation exists for the bees who live between the Tropics of Capricorn and Cancer; here, during the course of the year, the sun changes twice not only its altitude and its azimuthal angular velocity, but also its apparent direction of movement. Part of the time 116 . "Ti "' '-'¢ rs' 73' 6’0" a“ ' ,4” r ,h V i I /% ll 20 / T Bombay E l" ‘i’ A! Poona I y Y Al" / / /. FIG. 61. In Ceylon, bees were trained for a week to feed in the north just as the sun was crossing the meridian (April 16—23). During this time, the sun was north of the zenith, as seen from Ceylon. night of April 23—24, the bees were flmvn by air freight to Poona, India, and released on the next day as the sun crossed the meridian. Now they searched for food in the south. This means they had mistaken south for north, because the sun appeared correspondingly displaced in the sky. H7 During the Munich in June 1955, bees. At this time ofthe year in Ceylon the sun moves across the sky north of the zenith. In Munich I trained these Indian bees in the usual way, in the afternoon only, to fly to a feeding place 200 meters to the south of the hive. The bees obviously noticed that something was wrong because the sun was moving through the heavens in the opposite direction from usual: the next morning they were completely disoriented; they could no longer find the southerly direc- tion. Four days later I repeated the training procedure, with the same result. sition——-accurately to the south. Thus they proved that they were capable of taking account of the fact that the path of the sun was clockwise in Munich, directly opposite to its counterclockwise course in Ceylon. It would be of great interest to know whether the bees that “calculated” correctly after 43 days were newly hatched individuals, or workers that had had flying experience be- fore the experimental transplantation. Unfortu nately, all collector bees that had been marked in Ceylon d' ' ied durin g SPECIAL PROBLEMS CONCERNING Sonia ORIENTATION to Brazil. The oflspring, which grew up in Brazil, were subjected to the previously described displacement experi- ment of von Friseh. According to Kalmus, these North American bees oriented themselves in the Southern Hemi- sphere approximately as their ancestors had done in the Northern Hemisphere. In other words, they took the sun’s course in the south to be clockwise instead of vice versa. It was concluded that this inborn calculating mechanism must be inherited through many generations; only in the course of several centuries would a change-over be possible, based on mutations in the sexual adults (Kalrnus, 1956, pp.563—564) This conclusion would present a dilemma, at“ least for those bees whose homes lie between the tropics. As already mentioned, the sun, as seen from a fixed observation point on the earth, changes the direction of its path twice a year in these areas. The bees would therefore have to have two kinds of inborn calculating mechanisms, and accurate knowledge of when to switch from one mechanism to the other would also have to be inherited. Since the life span of a bee is only 4~—6 weeks, different generations should inherit different calculating mechanisms. During my stay in Brazil, I took the opportunity to repeat the experiments of Kalmus, in the same place, and with bees likewise transported from the Northern to the Southern Hemisphere. Despite painstaking care I was un» able to confirm the results of his experiments. Apparently some technical differences in the experiments caused the discrepancy in the results. I’Vhen we investigate the orientation of the bees by solar compass, through displacement experiments, we take care—-— after long years of experience—to observe the following precautions: I19 i I l l I s 5 : bees that could accumulate enough experience in solar orientation~~—are included in the experiment. (2) On the training day, the colony is not moved into the training area before noon; then, howey diately with the directional trainin . . location is situated at least twice the flight radius of collector bees (:36 kilometers) from the old location. It is known (Wolf, .1926, 1927; Uchida and Kuwabara, 1951) that displaced bees return to their old home as soon as territory on their searching flights. (4) Each collector bee should be individually marked with numbers; and we demand that each numbered bee frequent the feeding table for at least 3 hours without pause. It appears that this is the only way we can be certain that the bees are well trained, that is, that the training direction is firmly imprinted on their memory. Lazy collec- tors are caught, killed, and replaced by better ones. Since Kalmus, as far as we can see, did not observe these precautions, and since our experiments showed an unam- biguous result (Fig. 62), we must again conclude that the they enter familar location cannot be completely innate. Of course, each bee will instinctively, on all her flights, observe the position of the sun and its change in angle. But its apparent speed and 120 -..._ _-'.-. __ .- Srecm. PROBLEMS CONCERNING SOLAR ORIEN'I‘A'I‘ION direction of movement must be learned according to the location. Experiments of another type will confirm these results. “w Orientation of Bees Raised Without Sun ~ One can let bees hatch in an incubator, and then raise them in the absence of daylight in the cellar by artificial illumination (the day-night rhythm is automatically regu- lated through a time switch). If it is true that: bees must learn locally the calculation of the path of the sun, then such cellar bees should not be able to use the sun compass in their flights during the first days in which they are al- lowed out of doors. And this is actually the case. i l took bees that had been raised for 4 weeks in artificial light, without sun, out of the cellar into the field at noon, opened the flight entrance, and trained 30 foragers to a feeding table 180 meters to the south. When on the follow- ing morning, removed to a strange territory, they were given the Opportunity of finding the training direction (south) they were disoriented. The feeding table to the south was not more heavily visited than those set up in the north, east, and west (Fig. 63). These bees, reared without sun, thus behave differently from experienced collector bees. The same bees were then allowed to fly freely for 8 days in the sun, and afterward the same tran3position eXperiment was repeated. This time, after displacement, the collectors flew accurately in the training direction to the south, thereby showing that they had [earned the sun’s course within 8 days. It would be interesting to know in detail how the bees learn to calculate the sun’s course. Do they observe the altered position ofthe sun from time to time throughout the 12} l Ct‘)rntts.\'1c.-tTro.\‘ Ammo Soemt BEES day, and combine this with their exceptional time sense? Or is it sufficient that they become aware of only a part of the sun’s course, with its characteristic direction of move- ment and its speed, in order to calculate from this the other sectors of the arc? The following experiment will explain the process that actually takes place. A new colony was raised in the cellar in the absence of sunlight, and after 4: weeks brought again into the daylight. These bees were allowed to see only the aflaraooa ma each day; mornings and evenings they were kept in the dark cellar. This was repeated for 35 days. In this way the bees were given the opportunity to commit to memory only the afternoon course of the sun. At this point, they were tested to Test Period Feeding Period (124.57) 06.4.57) 5 W 0 2 SE to Q; Q: 41') NE 780 33‘. q 84 NW ;2 _ (a) 3 .9 IO N 121314151617” FIG. 62. Two diSplacement experiments in Brazil, with bees whose ancestors came from North America. The bees were trained to the northwest in the afternoon. On the following morning, after dispiace~ Inent into a strange territory, they again flew to the food table in the training direction. Therefore they had calculated the path of the sun (Continued on mitt page} 122 ' - - ’ W-hu-vu-wuv u ~.— . . 5‘.— .r— 2"". SPECIAL [moments CONCERNING SOLAR. ORIENTA'TION see whether they could find, in the morning, a compass point learned by training in the aflemooa. They were again trained in the afternoon, to a food source in the south, and shifted in the evening to strange territory. In the morning, on the test flights, they were exactly oriented to south. Thus they showed that they could calculate“ the sun’s position in the i‘orenoon, extrapolating from their information about a small part oft/re sun’s course in the afternoon, and this when {he} never before in their am had seen the morning sun. The same Test Period Feeding Period (29.3. 57) (2813.57) SW SE NE U) 8 Q “o lb :3: g D “‘6: NW 3 (b) a 9 10 a 1213 M 15 I6 17 16” according to their location, and not according to their ancestral land of origin. (As in the experiments of Kalmus, the bees used in experiment (a) were the descendants of a queen bee that had been imported from North America a few weeks before. The bees used in experiment {31‘} were descendants ofa queen bee that had been imported from North America 4 years before. 123 FIG. 63. Results of three dis- placement experiments on bees that were raised without son in an artificially lighted cellar. The training direction was 0 o 0 south. Each dot above a feeding o o 0 table stands for one captured bee. The bees were unable to ? calculate the sun’s course. page 95). In order to analyze the learning process more exactly, I computed the necessary interval of time for the free flight. This was done over a period of eight afternoons. In addition, the number of flights was recorded. A marked collecting I24 FIG. 64. After the eellar- ‘ reared bees had been trained for live afternoons in the open, most of them were able to ori~ ent themselves in the training direction in an unknown terri- tory. Although they had never seen the sun in the morning, they were able to calculate its position correctly even in the morning. -(>I swarm was attracted to a feeding table in the south, and all the collecting flights of each bee were recorded. The results showed that, for bees raised without sun, one afternoon outdoors with about 60 collecting flights was not so flicient for learning sun orientation. After about: five afternoons, with a total of 500 eolleeting flights, the learning period for sun- compass orientation was almost finished (Fig. 64). By this means we found one ofthe first stages oflearning in bees raised without sun. Bees that had experienced three afternoons of training, with about 300 flights, had learned 125 COMMUNICATION AMONG SOCIAL BEES something, namely, to take into account the angle between the sun and the feeding place. The feeding place was located to the south and the afternoon sun was to its right. The next morning the bees, released in strange territory, did not fly to the south, but showed a preference for an easterly direction. In other words, they flew true to a solar direction, in such a way that they had the sun again to their right, as on the previous afternoon. This direct “angle- orientation” by means of the solar compass appears to be the first step in the process of learning. After that the bees then learn in addition to calculate the sun’s course and its correct azimuth (Lindauer, 1959). ~ The Solar lompass in Competition with Terrestrial Landmarks ~ Now that we had learned the importance of the solar compass for the orientation of bees, we tried to set up land.- marks to compete with the sun as reference points for orientation. It has long been known that bees also use land- marks for their orientation—a tree, a path, a forest margin. Again we made use of the displacement experiment. This time, however, we placed our bee colony on the edge of a wood that ran in a straight line from north to south and bordered on a large, open field. The bees were then trained to a feeding table 180 meters to the south, so that they had the noticeable wood to their right during the flight to the feeding place( Fig. 65). Then we moved the colony over— night to another area, whose chief landmarks were similar to those of the training place. Here the edge of a wood also bordered on an open field, but now the wood ran from east to west instead of from north to south (Fig. 66). The entire landscape was thus turned through an angle of 90°, while 126 -—|: ...- SPECIAL PROBLEMS ("loner-swine SOLAR ORIENI‘ATION the sun remained in its usual course. Would the bees be confused by this striking landmark, or would they be di- rected by their solar compass and fly out into the open field? The result was conclusive: the bees were almost unani- mously led astray to the west by the edge of the wood. The FIG. 65. The bees were ofl‘ered noticeable terrestrial landmarks during training. In this esperiment, they had the edge ofa tall wood to their right during their flights to the food table. 127 COMMIENECA'I‘ION Astosc 80cm. BEES sun lost out t0 the terrestrial landmark (yon Friseh and Lindauer, 1954) We repeated the experiment, but this time we set up the hive 60 meters from the edge of the wood and trained the bees as usual to the south. The result was the same. But at a distance of 210 meters, when the wood was to be seen as a narrow shadow-contour only 3--4° above the horizon, the bees no longer observed the edge of the wood as a ,2: 41$ gays ., __ 58.0.? .... 52:” g - \IBOm ta... 5 ——§: FIG. 66. On the next morning, the southerlywtraincd bees (Fig. 65) were confronted with a similar terrain, but this time the wood ran east and west instead of north and south. lVIost bees were lead astray by the terrestrial orientation clues leading west; only a few followed the solar compass. (Numbers at the feeding places indicate numbers of visiting bees captured there.) 128 ._-.._ a—nuu,-__ -.-. . SPECIAL PROBLEMS Coscessisc SOLAR Oaits'mrios guiding line, but they followed the solar compass out into the open field. We also set up other landmarks in competition with the sun. When we trained the bees on the shore of a lake, which ran in a straight line from east to west, and then on the next morning freed them in another area where the landscape was rotated through 90°, they were again led astray by the terrestrial landmark. All flew to the south, because they had noticed the striking shoreline to the left of their path of flight. The sun also lost out when we trained the bees along a street and repeated the experiment the next morn- ing along another street that lay at a 90° angle to the first. A characteristic of these dominant landmarks was that they led the bees in an unbroken line from hive to grail. In an additional experiment we offered the bees landmarks of another kind. In the training, a large tree stood in the middle ofthe path offlight between the hive and the feeding place, and it was a particularly striking landmark in the middle of an open meadow. On the next morning, the displaced bees flew out of the hive and saw a similar tree standing in the ficld.--not, however, in a southery direction as on the previous day, but to the east. This time the bees did not bother with the beckoning landmark in the distance, but followed the solar compass and flew to the south (Fig. 67). A rather large group of trees, which lay between the hive and the feeding place, and which on the next morning was correspondingly transposed, was likewise unable to com— pete with the solar compass (Fig. 68). We hope in the future to obtain a more exact picture of the importance of different landmarks. Perhaps there are some that are an equal match for the solar compass; but to establish this many additional experiments are necessary. I29 FIG. 67. The bees were not led astray by such COMML'NICA'I‘ION AMONG Socru Bras f80m .l T@ l landmark as a single tree; in this case they solar compass. a striking orientation faithfully followed their 3. —.——.. ‘fi-fi—“maq— ..\. _. SPthiAI, PROBLEMS Commch SOLAR Ommrrriox ~ Conclusion ~ When Professor von Frisch reported, in 1946, that bees can inform each other in the dark hive about the position of any point in the surrounding territory, through directed, rhythmic tail-wagging dances, nobody suspected in their first amazement what a wide field for future investigations had been opened up by this discovery. At first the discovery seemed to concern only compara- tive animal psychology, since it was a completely new mode of communication, unique in its rich symbolic content. But soon new problems and possibilities appeared in the realm of sensory physiology: it was necessary to investigate the specific sensory faculties that are the basis of this commu- nication system. In the course of this investigation, new high levels of accomplishment in insect sensory organs were discovered, which nobody would have anticipated before. Finally, the question of the phylogenetic deve10pment led us to undertake studies in “comparative linguistics” among the taxonomic relatives of Apr; melly’era. And in carrying out these studies, we have already found several ' modifications and some primitive rudiments of the honey- bees’ dance, as well as new forms of communication that can be considered independent sidelines of deve10pment, branching from the common primitive elements of the bee’s dance. With such investigations, it has been shown that phylogenetic research is possible even in the field of such highly developed behavioral characteristics—which do not leave paleontological traces, such as fossils, as proof of their part in phylogenetic history. ...
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