Movements of Australian flying foxes (Pteropodidae: Megachiroptera).

MOVEMENTS OF AUSTRALIAN FLYING FOXES (PTEROPODIDAE: MEGACHIROPTERA) By J. E. NELSON* [Manuscript received July 20, 19641 Summary Evidence is presented to show that the coastal species Pteropus poliocephalus and P. gouldi congregate in large camps from early until late summer. In these large summer camps the young are born and raised, the sexes become associated, and conception occurs. The numbers within these camps are influenced by the availability of blossom in the surrounding area. The adults are normally dispersed during the winter while the immature form winter camps. These camps contain a larger percentage of adults in those winters in which blossom is more abundant. The inland species P. scapulatus forms large camps in early summer but the young are born in autumn when the population is dispersed. Since the food supply of P. scapulatus is less dependable and undergoes greater fluctuations than that of the coastal species, P. scapulatus is more nomadic than P. poliocephalus and P. gouldi. Flying foxes (fruit bats) hang during the day in trees within an area called a "camp", and at night move into the surrounding countryside to feed on nectar, blossoms, and fruit. These daily movements are well documented (Willey 1904; Jameson 1909; Allen, Lang, and Chapin 1917; Ratcliffe 1932; Ferrar 1934; McCann 1934; Sanborn and Nicholson 1950; Kulzer 1961) but little is known of the seasonal movements of Megachiroptera. Seasonal patterns of movement have been inferred from the progressive occupation of camps over the range of the species, but have not been studied by the recovery of marked individuals. These seasonal movements have been associated with food and climate. Jameson (1909) correlated movements of Epomophorus wahlbergi with the ripening of certain African fruits; Allen, Lang, and Chapin (1917) suggested that the heavy seasonal rains may cause Eidolon helvum to move from the area. Sanborn and Nicholson (1950, p. 316) considered that fluctuation in numbers within camps of Pteropus ornatus in New Caledonia "does not indicate a true migration; rather, simply a seasonal movement instigated by the presence or absence of food". Ratcliffe (1 93 1, p. 26); after examining the Australian species, concluded : "The extensive migrations of the little red fox, P. scapulatus, are almost certainly governed by the blossoming of the so-called hardwood trees. As this is notoriously uncertain, the movements of this species show a considerable irregularity"; and again on p. 24 "P. poliocephalus carries out very regular, seasonal migrations, moving southward in the spring into southern Queensland and New South Wales . . . Beyond the fact (made apparent by the periodic desertion and re-occupation of well-known camps) that this seasonal migration does take place, the available information is scanty". * Zoology Department, University of Queensland; present address : Department of Zoology and Comparative Physiology, Monash University, Clayton,Vic. Aust. J. Zool., 1965, 13, 53-73 54 J. E. NELSON The summer range of P. poliocephalus extends from Rockhampton (central Queensland) to Victoria. Ratcliffe found winter camps of the species only between Rockhampton and the Mary River 200 miles south of Rockhampton. Thus, the regular migration of P. poliocephalus would result in a very dense population being restricted each winter to a fraction of the summer range and would necessitate an area where blossom and fruit were abundant. Preliminary observations indicated that blossom and fruit production throughout the range of P, poliocephalus was at a low level at this time. The migration, therefore, may involve only a small section of the population. This possibility was investigated by examining the northern portion of the range of P. poliocephalus in the winter months, and by observing the changes throughout the year within camps in south-eastern Queensland. 11. MATERIALS AND METHODS During this study, observations were made on three species of Pteropus which occur in south-east Queensland: P. poliocephalus Temminck 1825, P. gouldi Peters 1867, and P. scapulatus Peters 1862. In an area within 100 miles of Brisbane there are at least 10 camps each containing in mid-summer about 20,000 individuals. Camps at Eagle Heights, Fisherman I., Beenleigh, Slacks Creek, and Currumbin Creek in Queensland, and Murwillumbah in New South Wales (Fig. 1) were visited every 2-3 weeks during 1961, and at least every month during 1959, 1960, and 1962. Rough estimates of numbers within the camps were made after walking around the edge of the camp and observing changes in the occupied area and after traversing the camp and noting numbers in marked trees. Attempts to estimate numbers by photographing flying foxes in the air after firing a shotgun were unsuccessful as many did not take to the air. Irregular visits were made to camps outside the study area and questionnaires were sent to centres throughout the state to obtain information on the time of occupation and the fluctuations of numbers within the camps. The movements of flying foxes could not be studied by catching and marking flying foxes individually since the chances of recovery of the small numbers that could be caught in the rain forest canopy would be very small. In an attempt to study the short-term movements of the animals, the camp at Fisherman I. was sprayed with the dye rhodamine red from a crop-dusting plane in November 1961. The rapidity with which food passes through the simple alimentary canal of flying foxes has been commented on by several authors (Dobson 1878; Allen, Lang, and Chapin 1917; Ratcliffe 1932). In laboratory animals the passage of food took 40 min. Since solid materials such as seeds and stamens are only slightly damaged in the gut, the relative importance of fruit and blossom at any period could be ascertained by the percentage of faecal pellets on the floor of the camp which contained seeds or stamens. For information on maturity and the reproductive state, 719 specimens (384$, 3359) of P. poliocephalus were obtained throughout the period December 1958-June 1961, and 560 specimens (2213, 3399) of P. scapulatus were obtained during the period from December 1958 to April 1959. P. gouldi occurs in very small numbers MOVEMENTS OF AUSTRALIAN FLYING FOXES 55 (50-200) within the larger P. poliocephalus camps (5000-20,000), and so only occasional specimens were obtained. MOORE 0 WARRIL BANK CHEVELLUM . GLASSHOUSE :: 0 SAMFORDO FISHERMAN I. 0 BRISBANE GOODNA C SLACKS CK *)r GILBERTON BEENLEIGH %? EAGLE HEIGHTS* ALLORA 0 LEGUME 0 MURWILLUMBAH* 20 MILES I Fig. 1.-Map of the study area showing the location of camps mentioned in the text. The reproductive organs and scapular glands were removed as soon as possible after shooting, and placed in Bouin's fluid. All sections were cut at 7 p and stained in haemotoxylin and eosin. Body weights were measured to the nearest gram, testes weight to the nearest 0.1 g, uterus weights to the nearest gram, and forearm lengths to the nearest millimetre. The bacula of 91 males were dissected out and measured to the nearest 0.1 mm. J. E. NELSON BLAIR ATHOL. Fig. 2.-Map of eastern Australia showing the known distribution of P. poliocephalus (close hatching) and P, gouldi (wide hatching). The distributions in this and in Figure 3 are based on the author's observations, Queensland Museum, Australian Museum, and National Museum of Victoria records, and on local reports. MOVEMENTS OF AUSTRALIAN FLYING FOXES 57 In a series of experiments designed to test the effect of the ambient temperature upon the descent of the testes, flying foxes were placed in wire mesh cages, 50 by 50 by 100 cm, in a constant temperature room where the ambient temperature could be varied over the range 20-35°C (10.5 degC). Temperature measurements were made to the nearest 0.1 degC using a thermistor unit assembled to the design of McLean (1954). 111. DISTRIBUTION OF SPECIES The distributions of P, poliocephalus and P. gouldi are shown in Figure 2, and of P. scapulatus in Figure 3. Camps are very common in the coastal areas and are occupied regularly. In the western half of the state camps are rare and in some areas have been formed only once in living memory. Ratcliffe (1932) gave the Mary River as the southern limit of distribution for P. gouldi, and today this is the southern limit of camps in which P. gouldi is the dominant species. But it is also found in small numbers (50-500) in P. poliocephalus camps from Nambour in Queensland to Murwillumbah and Legume in New South Wales. Only small numbers of P. poliocephalus are found in P. gouldi camps from Maryborough to Rockhampton. In the coastal areas, P. scapulatus may be found in camps of other species, or it may form its own camps. In those camps where two or more species occur, each species tends to be segregated from the other species. Camps of all species occur in rain forests, mangrove forests, Melaleuca swamps, alongside river banks or waterholes (in weeping willows, Salax babylonica, Casuarina spp., etc.), and occasionally in open forests. IV. RESULTS (a) P. poliocephalus (i) Fluctuations of Numbers in Camps The general pattern of the movements through the camps in the study area can be seen from Figure 4. There are two types of camps-summer camps and winter camps. (1) Summer Camps.-At first, the summer camps contain small numbers of flying foxes which remain for only a few days. For example, at Eagle Heights in 1961 there were none on August 31, about 200 on September 15, and none on September 17. In any one year there was some variation in the time from which the camps were occupied continuously. Usually Fisherman I. was occupied from early September, Murwillumbah from early to mid-September, Eagle Heights from mid-September, and Currumbin Creek from mid to late September. Latitude then did not appear to influence the time of arrival. During November and December there are large fluctuations within all camps. The decreases at Chevellum and Fisherman I. indicate a movement from these camps whereas the increases in the other summer camps suggest movement into these camps. These movements are irregular, varying slightly from year to year. In 1959, for example, Currumbin Creek was deserted from October 24 to December 6, and not J. E. NELSON -- Fig. 3.-Map showing the distribution of P. scapulatus in eastern Australia. MOVEMENTS OF AUSTRALIAN FLYING FOXES 59 occupied continuously until December 15 onwards. Other examples can be seen from Figure 4. In 1958, two camps which had not been occupied for 6-7 years (according to local residents) were each occupied for 2 weeks. The one at Moore was occupied for the first 2 weeks of November and the one at Warril Bank was occupied for the last 2 weeks of November. This indicates that there are movements into the study area, as well as movements from camp to camp in the area. r AF I I Y FISHERMAN I. SLACKS CK. BEENLEIGH EAGLE CURRUMBIN CK. MURWILLUMBAIHEIGHTS LOCATION OF CAMP Fig. 4.-Kites illustrating the variation with time in the population size of the various camps in the study area. Horizontal lines indicate the time of visits to the various camps. As seen in Figure 4, the maximum numbers in the major summer camps are attained in December or January. The decrease in numbers in late January at Eagle Heights, Currumbin Creek, and Murwillumbah indicates that the flying foxes are now leaving the camps. After March-April there is a further decrease. In 1960, all summer camps were deserted by mid-April whereas in 1962, although some camps were deserted for a short period about this time, most were not deserted until June. In contrast, Fisherman I. showed an increase in March-April 1961 and 1962, and in February 1961. Two individuals marked with rhodamine red at Fisherman I. on November 29, 1961,'were recovered at Murwillumbah in mid-February 1962. 60 J. E. NELSON No P. poliocephalus were found around Bundaberg in August 1958 (late winter) nor in the area between Bundaberg and Rockhampton in June 1961. Some P. poliocephalus were present in the P. gouldi camp at Bundaberg in February 1961. P. poliocephalus camps at Grafton and Imbil (see Fig. 2) were occupied from late September-early October to early April, with the population peak occurring in November, December, and January. Legume visited only on March 5, 1960, contained large numbers, and the Bunya Mountains visited on May 23, 1961, contained only 200-400. Thus, from the small amount of information available, camps outside the study area appear to be similar to those inside. The general pattern then appears to be a gradual increase in the camp population size from September to the maximum of December and January. In late January flying foxes begin to leave the camps, or possibly more leave than enter. From February to April the numbers remain fairly steady, while in April there is a marked decrease. In some years the camps are deserted at this time (i.e. 1960) but in others the numbers decrease at this time, may increase again in May, and then decrease again so that they are deserted by late June. Fisherman I., which has its minimum population while other summer camps are having their maximum, appears to be a camp en route to some other camp or camps. One of these camps is Murwillumbah; the camps at Moore and Warril Bank, and possibly Chevellum, were similar camps. This suggests that the large populations of December and January in such camps as Murwillumbah are composed of flying foxes from a number of small camps which are occupied only in early or late summer or both. One temporary camp of P. poliocephalus was present at Samford for 2 weeks in early February 1958. (2) Winter Camps.-Two winter camps were found in the study area. One at Slacks Creek was first occupied in April 1960, when the summer camps were being deserted; this camp was deserted in September 1960 when the summer camps were forming, was occupied again in January 1961 when the summer camps decreased, and was finally deserted in late June 1961 as were the summer camps in the area. The other winter camp was at Beenleigh and was occupied continuously from October 1961 to September 1962 when the study terminated. This camp increased in size in April 1962 when the summer camps decreased. Both winter camps had not been occupied (according to the land owners) for 5 or 6 years. (ii) Male Reproductive Cycle (1) Maturity.-When testes weights and bacula dimensions are plotted against body weight, both show a sudden increase between 540 and 650 g body weight, indicating that maturity in P. poliocephalus occurs at a body weight of 595i-55 g (Fig. 5). This corresponds with a forearm length of 145&5 mm (Fig. 6) and an age of about 18 months (Fig. 7). The maximum body weight recorded was 1016 g, and the maximum forearm length secorded was 164 mm. (2) Seasonal Changes in Male Reproductive System.-The seasonal variation in testes weight is shown in Figure 8. The seminiferous tubules and ducts of the epididymis are solid at birth and have a diameter of 12 p. Typical meiotic and mitotic nuclei are not seen until about the fifteenth month, when spermatocytes and spermatids MOVEMENTS OF AUSTRALIAN FLYING FOXES 61 are seen in the lumen of the ducts of the epididymis. At this time of the year (January) the testes of the mature males are approaching their maximum development. By the age of 17 or 18 months the ducts of the epididymis are filled with spermatozoa. BODY WEIGHT (G) Fig. 5.-The relation of body weight and testes weight of 307 male P, poliocephalus collected from January 1959 to June 1961. The symbol 0 represents mean of class with an interval of 100 g (e.g. from 101 to 200). The vertical line shows one standard deviation on either side of the mean. Fig. 6.-The relation of body weight to length of forearm in 315 male P. poliocephalus collected from December 1958 to June 1961. Symbols as in Figure 5. 50 Sperm were present in the epididymis of the mature male during every month of the year although their abundance varied with the testes weight being greatest during February and least in the period from June to September. Decreased spermatogenesis in the latter period was indicated by the decreased diameter of the I I I I I ! I 0 100 200 300 400 500 600 700 800 900 BODY WEIGHT (G) 68 J. E. NELSON Kogan (November), Eidsvold (December-January), Charters Towers, and Chinchilla (October). 1961 was a very dry year at Koolootah (7.5 in. rain fell compared with the average annual rainfall of 40 in.) and for the first time on record no P. scapulatus appeared. In dry years individuals were commonly found entangled in barbed-wire fences or drowned in water tanks in the western areas of the species' range, and were reported to be more common in the coastal areas. Small groups (1-500) of P. scapulatus were found at Charleville (March-April 1962), Hungerford (April 1962), Taroom, Springsure (1959), Mitchell, Clermont, and Aramac. These small groups were found near flowering trees or waterholes, and remained in the area from 1 day to 3 weeks. 0 i I I I I 250 300 350 400 450 500 BODY WEIGHT (G) Fig. 11.-The relation between body weight and testes weight of 182 male P. scapulatus collected from December 1958 to April 1960. The symbol 0 indicates mean of class with an interval of 50 g (e. g. 451-500). The vertical 1i.ne shows one standard deviation on either side of the mean. (ii) Male Reproductive Cycle Male P. scapulatus are mature at a body weight of 355 f 25 g (Fig. 1 I), a forearm length of 12315 mm (Fig. 12) and an age of 18 months. The maximum body weight measured was 604 g and the maximum forearm measured was 141 mm. The variation in testes weight over the period December-April is shown in Figure 13. Maximum testes weight occurred in December but the weight may have been greater in the preceding months when no records were obtained. The accessory sex glands were large during December and small from January to April. (ii) Female Reproductive Cycle Maturity in the female P. scapulatus occurs at a body weight of 325&25 g, a forearm length of 120rt4 mm (Fig. 14), and an age of 18 months. Maximum body weight measured was 560 g and the maximum forearm length obtained was 137 mm. Material was not adequate to determine the time of conception accurately. Conception probably occurred in late November and early December when males were seen marking and defending territories. Parturition occurs from late April to early May as all of the females shot on Ap1il25, 1962 had full-term embryos and one animal gave birth in the laboratory on April 27, 1962 (young was stillborn), and another gave birth on May 2, 1962. MOVEMENTS OF AUSTRALIAN FLYING FOXES 69 (iii) Correlation of Breeding with Movements Although the movements of this species are irregular there is usually a movement into camps .about the November-December period when copulation and conception occur. After conception the sexes segregate and may remain in the camp for a short period or move (in smaller numbers) to new camps or into the camps of other species. 300 350 400 450 5W BODY WEIGHT (G) Fig. 12.-The relation between body weight and length of forearm in 218 male , collected from December 1958 to April 1960. Symbols as in P. scapulatus Figure 1 1. 7 6 5 S - k i 4- $ fi 3ill k 2 0 1 I I I I JAN FEE. MAR. APR. MONTHS - - - - 1Fig. 13.-Showing the seasonal variation in testes weight of 92 male P. scapulatus collected from December 1958 to April 1960. Symbols as in Figure 11. Since only small groups have been found from February until September, parturition in this species, in contrast to P. poliocephalus and P. gouldi, occurs when the population is dispersed. 70 J. E. NELSON (iv) Diet The Forestry Department of Queensland has kept records of the flowering times of the spotted gum, E. maculata, in the Dalby district where it is a dominant species and a good indicator of general blossoming conditions in the locality. In December 1950 and October-November 1955 there was very heavy general flowering, and in 1959 there was a good flowering ranging from August to December. Light and scattered flowerings occurred in the between years. The general flowerings of 1950, 1955, 1959 correspond with the large numbers of P. scapulatus found at Chinchilla (and in other areas) in the summers of those years. As in P. poliocephalus, the maximum numbers of P. scapulatus occur when blossom is most abundant, i.e. in the summer. 0% PREGNANT O 33.3% PREGNANT 0 97.7% PREGNANT 0 100% PREGNANT 300 400 500 BODY WEIGHT (GI Fig. 14.-The relation between body weight and forearm length in 160 female P. scapulatus collected on January 18, 1959. Very small numbers were found in the study area in the poor blossom period 1960-61, whereas in the good period of 1961-62, P. scapulatus was present in most camps and formed a large camp at Esk from November to January, and at Glass House in January. There were large numbers in the study area in 1958-59 and none in 1959-60, a good blossom year in the study area but also a good period throughout the state. From the little evidence available, P. scapulatus appears in large numbers in the coastal area of south-east Queensland every 2 or 3 years, and has been reported in the Grafton camp every 2 or 3 years. Many correspondents stated that P. scapulatus was more common in the coastal areas in dry years, suggesting that they appear on the coast (where blossom is regularly available, though in varying amounts) when blossoming is poor inland. Since no camps of P. poliocephalus were found around Bundaberg in August 1958 or in the area between Bundaberg and Rockhampton in June 1961, the hypothesis that there is a regular mass winter movement into the northern part of the species range must be questioned. Further, there is no evidence of a progressive occupation of camps from Gympie in the north to Grafton in the south; and the variation in the MOVEMENTS OF AUSTRALIAN FLYING FOXES 7 1 times of arrival in camps in the study area was as great as those observed by Ratcliffe over the entire range of the species; (Ratcliffe reported that P. poliocephalus appeared in October in the northern areas, and in December in the southern parts of New South Wales). For example, Currumbin Creek was not occupied until mid-December 1958, while all other camps in the study area were occupied in October. While the evidence suggests that there is no regular seasonal migration, the fluctuation in numbers within camps during a year indicate that local movements are common. Moreover, the marking experiment provides direct evidence of a movement between Fisherman I. and Murwillumbah. The gradual increase and decrease in numbers in the summer camps indicate that these local movements involve small groups rather than large sections of the population.This is supported by the presence of small numbers in the camps for brief periods during the early and late stages of occupation. If the animals which leave the camps at the end of summer do not migrate north, we are faced with the question of what happens to them. Observations on other species of Pteropus provide some clues as to what probably takes place. Baker and Baker (1936, p. 126) referring to the movements of P. geddiei of the New Hebrides stated: "When females become pregnant about February, they leave these camps, and it becomes difficult for a time to obtain female specimens. For a time, the males continue to lead a social life . . . Later in the year, about June, when pregnancy is far advanced, the females may be found in inland camps which contain few or no males. At this season, males have given up their social life and live separately". Andrews (1900) discussing P. natalis from Christmas I. stated: "At this season, most of the females seemed to live in the deeper parts of the forest, and nine out of ten of the specimens shot on the coast were males". These observations suggest that the animals have a non-gregarious phase or season, starting soon after conception with a segregation of the sexes, and culminating in a dispersed and fragmented population. As there can now be little doubt that the great majority of the adult population of P. poliocephalus (and also of P. gouldi and P. scapulatus) do not remain aggregated in camps during the winter, it seems almost certain that they disperse, living either as individuals or in small groups. If the adults remained gregarious during the winter, their camps would certainly have been discovered, whereas a dispersed population of an animal with the flying fox's nocturnal habits would readily escape notice. It is not surprising, therefore, that there are very few observation which throw light on the location of the animals when the adults disappear from the camps. No relevant observations came to light on P. poliocephalus in the study area but some highly significant records of individuals and small groups of P. gouldi and P, scapulatus were obtained from many parts of Queensland, as has already been mentioned. Furthermore, Ratcliffe (personal communication) has reported that on 2 successive years within the past decade individuals of P. poliocephalus have turned up in Canberra in the early winter. Heavy night frosts (to which the flying foxes had apparently succumbed) were being experienced on both occasions. As the reduction in size and the breaking up of the main summer camps can be correlated with a decrease in the abundance of blossom, it seems safe to assume that 72 J. E. NELSON the stimulus for dispersion and the adoption of a non-gregarious existence is food shortage. It also seems safe to assume that the dispersed population is forced to become very largely nomadic. While most of the animals will probably stay within the broad region that included their summer camps, it is not unlikely that in the most southern parts of the species range, where the winter climate would be unfavourable and the food shortage severe, the movements would tend to be northward and (augmented by a fairly high mortality) might result in the equivalent of a seasonal migration. If the hitherto accepted idea of P. poliocephalus retaining its gregarious behaviour and carrying out regular seasonal migrations is discarded in favour of the hypothesis that has just been outlined, the annual sequence of events falls into the following pattern. Summer camps are formed when blossom is abundant, and hence when large populations can maintain themselves within restricted areas. In the early part of the season when blossom is still relatively scarce the camps are not as large as in midsummer and consist mainly of pregnant females and females with young. By December and January blossom is abundant and the population within most camps is at its maximum. Variations in the size of the summer camps during the period of their occupancy suggests that there are continuous movements of flying foxes between them. Some of the flying foxes found in the larger summer camps during the period of peak population come from smaller breeding camps (e.g. Murwillumbah from Fisherman I., as indicated in the marking experiment). The young, which are born in the early stage of the occupancy of the camps, begin to fly in mid-summer and thus can learn to fend for themselves at the time of the year when blossom is normally most abundant. The young move from the summer camps in March-April and form winter camps (in which a varying but usually small number of adults will also be found). Some adults start leaving the camps in late January and February when the food supply is decreasing and territoriality is being established. The main exodus begins after conception in late March-early April when the sexes segregate, soon to move off separately or in groups. The percentage of adults leading a dispersed and nomadic life during the winter varies according to the season. It is least in good blossom years when many will be found associated with the young in the winter camps. P. gouldi and P. scapulatus appear from the evidence available to have the same basic pattern of behaviour as P. poliocephalus, though the break-up of the summer camps of P. gouldi is not complete. A small number of animals continue to occupy them during the winter months. P. scapulatus, whose range includes much of the lower-rainfall inland, has had to adapt itself to a much more erratic and precarious food supply than the other two species, and shows evidence of being nomadic at times while remaining gregarious. The movement of flying foxes into camps when food is plentiful, and then a dispersal of the population when food is scarce would be a more efficient method of utilization of food supply than a concentration of the population within a small area of its range at the latter time. The ability to adjust their behaviour to the fluctuations in the food supply is one factor contributing to the success of the species. MOVEMENTS OF AUSTRALIAN FLYING FOXES 7 3 VI. ACKNOWLEDGMENTS The author would like to thank Dr. M. C. Bleakly, Department of Zoology, University of Queensland, for his guidance and support during this study; Mr. F. N. Ratcliffe, Division of Entomology, CSIRO, for his many suggestions during the preparation of this manuscript; Mrs. J. Lee for assistance in preparation of the figures; and Mr. Henry, Forestry Department, Brisbane, for information upon the flowering of various species. The project was supported by a Walter and Eliza Hall Fellowship in Economic Biology in 1960 and 1961, by a Commonwealth Post-graduate Fellowship in 1962, and by University of Queensland Research Funds. Preparation of the paper was aided by National Science Foundation Grant No. 23737. VII. REFERENCES ALLEN, J. A., LANG, H., and CHAPIN, J. P. (1917).--The American Museum Congo Expedition collection of bats. Bull. Amer. Mus. Nut. Hist. 37: 405-563. ANDREWS, C. W. (1900).-"A Monograph of Christmas Island (Indian Ocean)." Vol. 8. (British Museum (N.H.): London.) BAKER, J. R., and BAKER, Z. (1936).--The seasons in a tropical rain forest (New Hebrides). 3. Fruitbats (Pteropidae). J. Linn. Soc. (2001.) 40: 123-40. DOBSON, G. E. (1878).-Catalogue of the Chiroptera in the Collection of the British Museum(N.H.). (British Museum (N.H.): London.) FERRAR, M. L. (1934)-Daily flighting of flying foxes (Pteropus giganteus Briinn). J. Bombay Nut. Hist. Soc. 37: 214-5. JAMESON, H. L. 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