354 C . JONES

Some general ecologic data on West African pteropids have been presented by Aellen (1952), Eisentraut (1942, 1956, 1963, 1964), Rosevear (1965), Brosset (1966a), Hayman (1967), and Jones (1971); several of these authors also provided summaries of important earlier works. In addition to the aforementioned authors, others have published on various aspects of the biology of pteropids. Some important reports and reviews on temperature regulation were made by Eisentraut (1940), Robinson & Morrison (1957), Morrison (1959), Bartholemew, Leitner, & Nelson (1964), and Kulzer (1963, 1965). Brain sizes of several species were measured and compared by Findley (1969). Observations on roosts were given by Allen, Lang & Chapin (1 917) and Ogilvie & Ogilvie (1 964). Data on reproduction were presented by Matthews (1942), Asdell (1964), and Mutere (1967). Information on seasonal movements was provided by Nelson (1965~) and Mutere (1967). Behaviour of Australian pteropids was studied by Nelson (19653) ; anecdotes on behaviour were included in numerous reports by other authors. Information on dispersal of plants by bats was summarized by Van der Pijl (1957, 1969).

The purposes of this report are to present, discuss, and compare the data on as many aspects as possible of the ecology of three sympatric species of pteropids, Eidolon helvum (Kerr), Epomops franqueti(Tomes), and Micropteropuspusillus (Peters), in Rio Muni, and to compare the sedata with some of the information available on pteropids from other regions.

It is not within the scope of this brief report to present a complete summary of the mass of literature containing information and notes onall aspects of the biology of the pteropids discussed herein. References are given in the text that contain either additional information or examples pertinent to the purposes of this paper.

Materials and methods The data on Eidolon helvum, Epomops franqueti, and Micropteropus pusillus presented herein

were obtained mostly from studies of wild and captive bats in the vicinity of Bata, Rio Muni (Republic of Equatorial Guinea). Some information was taken from the literature. Observations of wild pteropids, especially roosting and feeding activities, were made in July and August 1966. Detailed studies of captive bats, as well as additional observations of wild animals, were conducted from February 1967, until July 1968.

Pteropids were located generally by one or more of the following methods. Roosting and feeding sites were detected by searching the area studied for bats and signs of animals, such as droppings beneath trees, partly eaten fruits, and potential roost trees. Animals were found frequently by following sounds of feeding, vocal sounds, and noises made during flight. In- formants helped to locate roosts of bats. Efforts were made to find and observe pteropids during the day, as well as at night.

Pteropids were observed with the unaided eye and with 10 x 50 Bushnell binoculars. Animals were watched at night with the aid of either a 6-V, sealed beam spotlight or with a head lamp.

Although some specimens were shot, most bats were collected in mist nets placed either beneath or adjacent to the foliage of trees in a patio. Nets were supported by bamboo poles and set 0-2 m and 4-6 m above the ground. Routine procedure was to check nets periodically, usually at 0.5 to 1 h intervals, during the approximately 12 h of darkness in Rio Muni. Sometimes nets were maintained constantly when numerous large bats were flying about.

Captive pteropids were housed in cages 60 x 60 x 90 cm, with wooden sides and fronts and 6 m wire mesh on the tops, bottoms, and backs. Cages were on legs 30 cm tall. Each cage included either a wooden shelf 10 cm wide or a dowel 3 cm in diameter that extended across the cage near the top. All cages were located outdoors beneath a corrugated metal roof.

ECOLOGY O F THREE PTEROPIDS 355

The animals were maintained on peeled and cut, as well as entire, fruits of bananas, plantains, avocados, and papayas. Fresh food was either placed on the bottom or suspended from the top of each cage every day about 1 h before dusk. Water was provided ad libidtrm in dishes about I cm deep set on the bottom of the cage near the back.

Measurements of bats presented herein were taken from fresh specimens. Measurements of wings and computations of wing loading were made according to the methods of Vaughan (1959). Linear measurements were taken with dial calipers. Animals were weighed with an Ohaus triple beam balance. Because differences were apparent between the sexes, data for males and females were separated.

Body temperatures of bats, as well as ambient temperatures, were taken with a YSI thermister thermometer and appropriate probes. Before each use, the thermister thermometer was calibrated and readings were compared with air temperatures taken with a pocket thermometer and a Taylor maximum-minimum thermometer. All temperatures were recorded in degrees centigrade.

Body temperatures and ambient temperatures were recorded while bats were housed in the aforementioned cages, as well as from animals placed in a Stokvis commercial electric refrigerator. Pteropids in cages were not restrained; animals placed in the refrigerator were taped to blocks of wood. To obtain temperatures, bats were restrained and probes were positioned as described by Reite & Davis (1966). Body and ambient temperatures were recorded concurrently. Temperatures were taken only of animals that seemed in good health; data from bats that died within 10 days after temperatures were taken were not included herein. Because no apparent differences were detected between the sexes with regard to body temperatures, data for males and females were combined.

Nomenclature of bats used herein was taken from Rosevear (1965). Most of the names of plants were taken from Guinea (1946).

Results and discussion The information presented herein was obtained mostly from direct observations of either

wild or captive pteropids in Rio Muni. Because of some differences in emphasis of studies and some differences in habits exhibited by the species that influenced observations, the data were not always completely comparable with regard to what was learned about each species studied.

Distribution Eidolon helvuni occurs throughout most of sub-Saharan Africa, including the islands in

the Gulf of Guinea, to about 30°S, but the distribution of this species is localized (Rosevear, 1965; Hayman, 1967; Mutere, 1967). At the limits of the aforementioned geographic range, these bats are considered occasional migrants rather than residents (Rosevear, 1965). In Rio Muni Eidolon occurs commonly along the coast and large rivers (Jones, 1971).

Epomops franqueti is known from Ghana east to Congo (Kinshasa), Uganda, north- western Tanzania, south to Zambia and Angola (Hayman, 1967). This species is reported from along the coast and in the interior of Rio Muni, but is most common near the coast (Jones, 1971).

Micropteropus pusillus occurs from Senegal east to southern Sudan, western Kenya, northwestern Tanzania, Uganda, Congo (Kinshasa), and Angola (Hayman, 1967). This small pteropid is known from only near the coast in Rio Muni (Jones, 1971).

Relative abundance For the three species of pteropids studied, some differences were noticed with regard to

the relative abundance of bats at the primary study site (Table I). Bats were sampled by

356 C . JONES

TABLE I Bats per nighi taken each month and ioial number of bars of each species taken per night. Total number of nights of

neiling bars is given in parentheses for each nzonih

- 0.18 Eidolon helvum - - 0.66 0.67 0.38 - - -

Epomops franqueii 0.66 0.24 2.33 1.67 0.69 1.25 - - 0.50 0.65 Micropteropus pusillus - 2.44 2.33 1.17 0.94 - 0.50 - 0.33 1.37

Total 0.66 2.68 5.32 3.51 2.01 1.25 0.50 - 0.83 2.20

mist netting during nine months; Epomops was netted in seven months, Micropteropus was obtained during six months, and Eidolon was captured in three months. Of the total number of bats sampled in mist nets, Micropteropus was more abundant at the study site thaneither Epomops or Eidolon. Although specimens were obtained from only two localities, Micropter- opus was the most common pteropid in Rio Muni (Jones, 1971).

Pteropids were not equally common throughout the year at the main study site (Table I). Bats were obtained most commonly from March through June; the peak of abundance of animals netted was in April. None of the three species studied was collected in October.

The seasonal fluctuations in the abundance of the bats studied were correlated with seasonal differences in monthly precipitation. The heaviest rainfall recorded during this study occurred in October. However, considerable rain fell during March, April, and May. The least rain was recorded in July and August. For a complete summary of rainfall, as well as other weather data, for 1966-1968 in Rio Muni, see Jones & Sabater Pi (1971).

Seasonal differences in the numbers of bats netted were also correlated with the avail- ability of foods. Although some fruits eaten by the bats studied were available throughout most of the year, peaks of the abundance of fruits at the study area were concordant with the peaks in abundance of the animals. Micropteropus and Epomops were seen at all times of the year in the area studied. Eidolon was absent occasionally from this area (Jones, 1971). Data on seasonal distribution of Eidolon, probably correlated with availability of foods, were presented by Rosevear (1965) and Hayman (1967).

The data presented herein on relative abundance of the three species of pteropids studied undoubtedly reflect the method of sampling. Differential probabilities of bats being caught in mists nets have been well demonstrated for many taxa of bats, and depend on the species and the agility of the animals, which often reflects the stage of reproduction. In addition, manoeuvreability of some of the pteropids probably was influenced by the amounts of food carried by the bats.

Reproduction Subadult Eidolon were seen and collected frequently, but young animals either nursing

or clinging to females were not detected during this study. In Uganda, pregnant females were found mostly from October through February (Mutere, 1967). Testes of adult males collected in Rio Muni during May and June measured 20-21 mm in greatest length; testes of a subadult male captured in June were 5 mm in greatest length (Fig. 1). Mutere (1967) recorded the greatest weights of testes of this species between April and June; the maximum

ECOLOGY O F THREE PTEROPIDS

24r----1 ' ! ' I ' 1

- 16-

2 -

- u)

0, + c :: 12- f 0 0, - - + 0, 0

W

c

C 8-

4 -

0

35 7

- 0 - X

0 m e 0 -

t t 0 - -

I I I I 1 I I I I I I _ J F M A M J J A S O N D

X

x x

Months FIG. 1. Greatest lengths of testes of Eidolorr Iielviini ( x ), Epomops franqueti (e), and Micropteropris pusillris (0) collected in Rio Muni.

weights of testes corresponded to the peaks of abundance of spermatozoa in the epididy- mides and the season of mating of these bats in Uganda. Asdell (1964) reported that in Cameroon Eidolon mated at the end of the rainy season in October and November and births were in February and March. Mutere (1 967) reported that in Uganda birth of young during the dry season was avoided by the phenomenon of delayed implantation exhibited by Eidolon.

Lactating female Epomops were collected in Rio Muni during March and April. Males captured in May and June had testes that measured greater in size than testes of animals captured in other months (Fig. 1). Asdell (1964) and Brosset (1966a) suggested no fixed season of breeding for this species.

Young Micropteropus were obtained in March and April. Lactating females were collected in March. A female with a clinging young animal was captured in April. Pregnant females were netted in May and November. Some males collected in March, April, and November had small testes (Fig. 1). Asdell (1964) reported lactating females in May and a pregnant female was captured in February. Some measurements of fetal and young Micropteropus were presented by Jones (1971). This species may breed either throughout the year or mostly in March and April, as well as in November.

Roosting habits All of the wild Micropteropus found at roost were located 3-6 m above the ground in the

lower parts of trees or in shrubs. The bats were associated usually with dense foliage. The

358 C . JONES

animals were at rest with the wings wrapped around the body and across the face. During the day, Micropteropus was very inactive and seemed almost torpid. The eyes were often closed. The ears appeared erect, but no movements were noticed. When disturbed greatly, captive bats changed resting positions occasionally by holding a branch with the thumbs and swinging the feet to a new place. This species roosted mostly alone, but sometimes two animals were roosting adjacent to each other. Several animals usually roosted in the same tree. In captivity, two bats occasionally roosted close together.

The wild Epomops found at roost during this study were 4-6 m from the ground in large trees, usually Terminalia catappa. The animals hung from small branches near clusters of leaves. These bats had the wings wrapped around the body, but the entire head was free. During the day Epomops was apparently alert, but not very active. The eyes were usually open, and the ears were erect and moved frequently. Epomops hung frequently with feet on opposite sides of a branch; this method of hanging was not observed frequently for either Micropteropus or Eidolon. Epomops used the thumbs to grasp branches and leaves when moving short distances. Only single Epomops were observed at roost. Animals watched in captivity seemed intolerant of each other and roosted as far apart as possible.

Roosts of Eidolon were located 6-20 m above the ground in large trees. The bats utilized sturdy branches and fronds near the trunk and beneath the crown of the trees. These animals rested with the wings folded along the sides of the body with the tips of the wings folded back. Sometimes the wings were held in a half-folded position away from the body. Eidolon was very alert and active throughout the day. The eyes were open. The ears were erect and moving constantly. Some animals crawled about almost constantly in the roosts. When captive animals were disturbed, they crawled headfirst to another location to hang. Wild and captive Eidolon roosted in clusters. Roosts of these bats observed during this study varied in size from a few animals to several thousand bats. Branches and fronds were frequently broken by the weight of large numbers of Eidolon at a particular roost. In Kampala, Uganda, Eidolon roosted in gum trees, Eucalyptus saligna, and the population at peak times included an estimated quarter of a million animals (Mutere, 1967).

Eidolon roosted usually in Cocos nucifera, Elaeis guineensis, and Ficus sp. Occasionally this species was found in Terminalia catappa. Epomops roosted mostly in T. catappa. Micropteropus roosted in T. catappa, as well as small trees and shrubs. On several occasions the three species were observed roosting in the same T. catappa.

Night roosting was not observed for Micropteropus and Epomops. However, night roosts of Eidolon were observed on several occasions. Several animals rested about 8 m from the ground in a T. catappa and an E. guineensis. For two to three hours after dusk, bats con- stantly entered and departed from the aforementioned night roosts. Nocturnal activity of Eidolon was described by Huggel-Wolf (1965). No predawn activities were noticed at these sites. The night roosts were in an area where Eidolon fed frequently on fruits of Arctocarpus incisus and Anona muricata.

Foods Foods utilized by the wild and captive pteropids studied included fruits of nine kinds

of plants (Table 11). Fruits of cultivated plants provided to captive bats were eaten well by each of the three species studied. No preferences for any particular fruits were detected.

Fruits of four species of plants were eaten regularly by wild Eidolon and Epomops when- ever the fruits ripened. Eidolon was observed most frequently feeding on fruits of Arcto-

ECOLOGY O F THREE PTEROPIDS

T A B L E I1

Foods eaten by wild (+) and captive (0) pteropids in Rio Muni

359

Food Micropteropus Epomops Eidolon

Bananas Plantains Avocados Papayas Arctocarpus Anona Terminalia Mangijiera Ficus

0 0 0 0 0 0 0 0 +

-t + +

carpus and Anona; Epomops was seen feeding most frequently on fruits of Terminalia. Except for the tough peel that was torn off by the bats, mature fruits of Arctocarpus and Anona were consumed almost completely on the first night of attack. For fruits of Termin- ulia and Mangifera, bats ate the fleshy coverings. Of the ripe fruits of T. cutuppa that were picked up from the ground in August 1967, approximately 52 % had been chewed by bats. Some of these fruits had only a bite or two removed, but many had the covering nearly completely removed. The aforementioned fruits were described as chiropterochorous by Van der Pijl(1957), who presented a detailed discussion of the role of bats in dissemination of plants.

The lists of fruits eaten by wild bats presented herein undoubtedly reflected the habits of the animals, as well as difficulties in making observations of the bats feeding. For com- parison, the list of fruits eaten by Eidolon in Uganda included mostly cultivated plants, such as bananas (Musaceae), papaw (Caricaceae), muvule and figs (Moraceae), mangoes (Anacardiaceae), guavos (Myrtaceae), giant passion fruit (Passifloraceae), loquat (Rosaceae) and soursop custard apple (Anonaceae) (Mutere, 1967).

Feeding beha viour Micropteropus was observed feeding only in captivity. Food was held with a foot, the

thumbs, and the mouth. This species fed slowly and deliberately. Food was consumed by slow sucking action of the lips and mouth. The uneaten fruit pulp was dropped after fluids were removed.

Epomops was observed feeding mostly in captivity, but limited data were obtained by watching wild bats feeding at night. Food was held by one foot, the mouth, and wrists. Food was held between the wrists, with one wrist and the mouth, and in the pocket formed by the flight membranes when the wrist was in flexed position. These bats easily transferred food from pocket to pocket with the mouth. The thumbs were usually folded back and used rarely to support pieces of food. However, the animals frequently held onto a branch or leaf with one thumb while feeding. Food was eaten by sucking motions, especially of the lips and tongue. The lips were often extended around large pieces of food. The pulp materials were spit out. Epomops was the only pteropid observed carrying food materials in flight. These bats were found carrying entire fruits of T. catappa.

360 C. JONES

Captive and wild Eidolon were observed feeding frequently. Food was held mostly in the mouth. Occasionally food was held in one foot, and food was held rarely with the thumbs. These bats often hung by the thumbs and manipulated food materials with both feet and the mouth. These animals usually opened and began to eat large fruits, such as breadfruit and anona, at the bottom. While feeding, the bats clung with the feet and thumbs to the outside of the fruit or adjacent branches. Usually a single Eidolon fed on the fruit for several minutes and was then replaced by another animal. Frequently other bats were either flying nearby or hanging in the tree near the fruit being eaten. Animals left the feeding site by dropping off the fruit and taking flight. Bats arrived at the feeding site by landing either on the top of the fruit or on adjacent branches and crawling over to the fruit to feed. When fruits of Arctocarpus and Anona were opened by Eidolon, the bats fed until the fruits were either consumed completely or fell from the tree. Foods were eaten by Eidolon with much vigorous biting and chewing. Much noise was made apparently by sucking and smacking of lips. Although a considerable amount of chewed-up pulp was dropped beneath feeding sites, apparently most of the food material was ingested by these bats.

Defecating beha viour Observations of captive bats revealed considerable differences in the position of the body

during defecation by the pteropids studied. Micropteropus eliminated waste materials while hanging by the feet; fecal materials passed over the front of the body. Epomops occasionally hung by the thumbs, swung the posterior part of the body down, and defecated. The legs were not extended, and this general manoeuvre by this species seemed rather awkward. In addition, Epomops also defecated while hanging in the normal position. Eidolon hung by the thumbs, swung the posterior part of the body down, extended the legs, and dropped the feces straight down. This manoeuvre was made by wild, as well as captive, Eidolon. I did not see this species defecate while in any other position.

Defecation by the bats observed began usually within 1 h after feeding and ended mostly within 3 h of the end of feeding. Fresh droppings were deposited beneath roosts of these bats during the night and until about 09.00 hours each day.

Stra t ijica tion Heights at which bats were captured in mist nets indicated levels of flight of the animals.

The three species of pteropids studied flew mostly at different heights (Fig. 2). Eidolon was captured only at 4-6 m. Epomops was obtained in nets set at 4-6 m, as well as near the ground; 72.7 % of these bats flew at the former level, 27.3 % at the latter level. Of the

Eidolon 1 1

Epomops - Microptwopus h-,

I I I I I 1 0 20 40 60 80 100

Per cent captured FIG. 2. Pteropids captured in nets set at 4-6 m (open areas) and 0-2 m (solid areas) in Rio Muni.

ECOLOGY O F THREE PTEROPIDS 36 1

Micrupteropus netted, 90.3 % flew near the ground and 9.7 % were recorded at 4-6 m high. The aforementioned levels of flight corresponded to the levels of roosting and feeding

observed for each of the species studied. In addition, there were some correlations between the levels of flight and the abilities of flight observed and calculated for each of the species.

On the basis of the data presented, it seemed that the three species foraged and roosted in the same habitat at the same time, but for the most part utilized different strata in the habitat. Differences in utilization of separate parts of the habitat by the three sympatric species illustrated the evolution of mechanisms reducing competition and enhancing coexistence.

& m a I dimorphisn I

Considerable sexual dimorphism was apparent in the genera of bats studied. Size differences between the sexes were greater in Eidolon than in either Epumops or Micru- pterupus. For example, measurements of forearms of male Eidolon averaged 13.02 % longer than similar measurements of females; forearms of male Epomops averaged 3.78 ”/, longer than forearms of females and measurements of forearms of male and female Micruptrrupus overlapped nearly completely, but females averaged slightly longer than males. Comparable dimorphisms and similarities between the sexes of the three genera were revealed by coni- parisons of six external and several cranial measurements of these bats from Rio Muni tabulated by Jones (197 I). In one external and three cranial features, female Micrupteropus averaged slightly larger than males. Other differences, such as the presence of white shoulder patches in adult males, were apparent for Epomops and Micrupteropus. Pelages of adult male Eidolon were more colourful than the pelages of females. Some additional examples of sexual dimorphism of the pteropids studied were mentioned elsewhere in this report.

Brain size Data on endocranial volumes and foramen magnum areas of the three pteropids studied

(Table 111) were provided by James S. Findley (pers. comm.). As expected, there were direct

T A B L E I11 Brain size of three species of pferopids

Braincase volume Foramen magnum area (cc) (mm’)

Species d3 Y Y $8 Y3

Eidolon helvurn 2,915 2.179 25.29 28.1 3 Epomops franqueti 1.630 1.505 18.98 24.08 Micropteropus pusillus 0.527 0.601 14.18 14.50

correlations between body sizes and brain sizes; the larger bats had larger relative sizes of brains. For detailed discussions of comparative brain sizes of bats, relative brain sizes of bats and some other groups of mammals, as well as correlations between brain sizes and flight abilities of bats, see Findley (1969).

Some differences between the sexes were noticed with regard to brain size (Table 111). Endocranial volumes of male Eidolon and Epomops were greater than those of females of

362 C. JONES

these genera. For Micropteropus, the converse was true; the female has a larger endocranial volume than the male. In all genera, foramen magnum areas were larger in females than in males.

Flight Flight in Eidolon seemingly was slow, deliberate, and relatively non agile. These bats did

not change courses quickly, but flew in straight-line patterns. Eidolon appeared awkward during take-offs and landings. These bats began flight by dropping from trees that were either roosts or feeding sites; the drops observed ranged from an estimated 0.5 to 2 m. They landed usually in head-up positions by simply dropping either onto the tops of fronds or into masses of leaves near ends of branches. Flight of Eidolon was described by Rosevear (1965) as slow, strong, with regular beats, and with occasional short glides. Some observa- tions of flight of Eidolon in Uganda were presented by Ogilvie & Ogilvie (1964). A detailed study of flight of Eidolon was conducted by Kulzer (1968).

Flight in Epornops seemed purposeful and in a straight line, but with considerable agility. These animals changed courses quickly and frequently. These bats did not drop any appreciable distance at the beginning of flight. Flight was terminated with the animals landing in head-down, normal roosting positions. Epomops commonly flew in and out of crowns of trees and near the ground.

Flight of Micropteropus was rapid and agile. The erratic flight of this species resembled flight of some insectivorous bats. These animals were observed frequently flying beneath, between, and sometimes apparently through clumps of fairly dense vegetation. These bats began flight with direct take-offs from branches and landed in head-down positions. As mentioned previously, members of this species were observed hovering at sources of food. On some occasions, these bats hovered and fed on bananas hanging inside an open animal cage that measured 60 x 60 x 90 cm. Captive Micropteropus flew in circles inside cages of similar dimensions.

Micropferopls Micropferopls 2 Epomof Eidolon /i /--

0 5p mm

FIG. 3. Wing outlines of three species of pteropids.

Morphologic features associated with flight (wing loading, wing area, body weight) varied greatly among the pteropids studied (Table IV). Outlines of wings were prepared for visual comparisons (Fig. 3).

Both inter- and intra-specific differences in the features studied decreased from the largest to the smallest bats. There were more overlaps between Eidolon and Epomops in the

ECOLOGY O F THREE PTEROPIDS

TABLE IV Body weight, wing area, and wing loading for three species of pteropids

363

Specimens examined

Weight Wing area (g) (cm2)

Mean (4 dd) Minimum Maximum

Mean ( 5 ??I Minimum Maximum

Mean (5 66) Minimum Maximum

Mean (13 99) Minimum Maximum

Mean (1 2 dd) Minimum Maximum

Mean (14 99) Minimum Maximum

Eidolon helvum 254.48 139.36 112.40 520.25 328.20 819.00

1 1 3.92 545.28 59.10 495.81

141.20 591.65

Epornops franqueti 133.18 533.02 59.50 311.00

159.80 640.22

85.01 410.52 59.10 401.83

114.60 542.44

Micropteropus pusillus 20.21 142.15 10.50 11 1.06 21.50 118.27

21.99 155.16 10.90 100.10 29.40 184.21

0.344 0.216 0.313

0.209 0.120 0.236

0.249 0.160 0.250

0.181 0.149 0.21 1

0.142 0.095 0,154

0.141 0.109 0.160

values for wing loadings than between either Eidolon or Epomops and Micropteropus. For example, wing loadings of male Eidolon averaged only 27.62 % greater than loadings of male Epomops, which averaged 42.98 % larger than the values for loading in male Micropteropus. Values for wing loading of male Eponiops were greater than the figures for female Eidolon. Although wing areas of the former were smaller than wing areas of the latter, weights of the former averaged more than weights of the latter.

Differences between males and females in the aforementioned morphologic characters associated with flight were similar for the two large species of bats. Mean values for males of Eidolon and Epomops averaged larger than means for females of these genera. There were relatively few differences between male and female Micropteropus. Males had slightly greater wing loadings than females, but female Micropteropus averaged slightly heavier and exhibited slightly greater wing areas than males.

Some limited data on weight lifting capacities were obtained for the two smaller species of bats studied; no information was gathered for Eidolon. An adult female Micropteropus was captured with an attached young that weighed 10.9 g, 41-28 % of the body weight of the mother. With the addition of the weight of the young, the wing loading of this adult was increased from 0.149 to 0.210 g/cm2. The wing loading for this adult female with attached young was 23.81 % greater than the maximum wing loading determined for adult females

364 C. JONES

of this species (Table IV). Two adult male Epomops were captured while carrying fruits of T. catappa. The fruits weighed 39.3 and 51.5 g, 25.60 and 40.48 % of the body weights of the animals. With the addition of the weight of the fruit carried, the wing loading for one animal was increased from 0.244 to 0.306 g/cm2. This wing loading was 18.3 1 % greater than the maximum wing loading calculated for adult males of this species (Table IV).

40-

35

30

Thermal response The relationships of body temperaures to ambient temperatures in the bats studied are

depicted in Figs 4 to 6. Discrepancies in the amounts of data presented reflected the numbers of animals tested in various ambient temperatures. Of 10 Eidolon, 5 Epomops, and 8 Micropteropus tested, three of each species were exposed to reduced ambient temperatures.

I I I I I I . . .' ... .... . . * .. . : ... . . m- . . ..* . . .. .. 0 . ....

.. - ..: 0 .*

0 . ... . -

V I 1 1 1 I I 5 10 15 2 0 25 30

Ambient temperature (" C) FIG. 4. Body temperatures of Eidolon helvum recorded during this study.

Body temperatures recorded from undisturbed captive animals ranged mostly between 30" and 40°C; ambient temperatures ranged from 22" to 30°C. Differences between body and ambient temperatures for animals of each genus were : Eidolon 9"-10°C; Epomops 3"-11 "C; Micropteropus 2'43°C. These ranges of body temperatures were comparable to deep body temperatures reported for Pteropus poliocephalus and Syconycteris australis (Bartholemew, Leitner & Nelson, 1964).

ECOLOGY OF THREE PTEROPIDS 365

. ... 0. * * 0 . 35

8.. . . .. . . . . . . . .

I I I I 1 I 0 5 10 15 20 25 30

Ambient temperature ( "C)

FIG. 5. Body temperatures of Epomopsfuanyueti recorded during this study.

When animals were exposed to decreased ambient temperatures, variable responses to dropping temperatures were elicited from the bats studied (Figs 4 to 6). Body temperatures of Eidolon remained stable in ambient temperatures above lO"C, but dropped considerably in ambient temperatures of 2"-10°C. For Epomops, body temperatures declined generally in accordance with ambient temperatures; the former averaged mostly 10" greater than the latter. Micropteropus maintained body temperatures of at least 24°C in a range of ambient temperatures from 4" to 29°C.

Considerable shivering was observed for the bats tested; this was most pronounced in ambient temperatures of 1 0"-20°C. In addition, abdominal heaving, like panting, was noted for most animals, especially in the minimum ambient temperatures. For Eidolon and Epomops, the constant movements of ears and eyes observed under normal conditions were much reduced in low ambient temperatures.

All of the bats tested recovered fully upon warming at the termination of exposure to low ambient temperatures. All animals exhibited considerable shivering for about 15 minutes when returned to the cages after testing. No differences between the species tested were noticed with regard to rates of recovery.

Homeothermy has been demonstrated previously in several species of Old World bats. The data for Micropteropus were very similar to the information available for Pteropus poliocephalus (Bartholemew, Leitner & Nelson, 1964) and Macroderma gigas (Leitner &

366 C . JONES

4 0 7 - 1 - r - r -

35 -

30 -

25 - - 0 0-

E 2 g 2 0 -

c

h U

m 15-

10-

5-

. 0 . .. . . .. 0 .

0 . 0 . 0 . . w .

b .

FIG. 6. Body temperatures of Micropteropus pusillus recorded during this study.

Nelson, 1967). The data for Epomops and Eidolon indicated more variable responses to low ambient temperatures than were observed for either Micropteropus or Pteropus and Macroderma. Variations in thermoregulatory abilities of bats as reflections of different physiological states of the animals studied were discussed by Studier & Wilson (1970).

Behavioural thermoregulation Some, if not all, of the observed daily activities of the bats discussed herein were appar-

ently either in response to or correlated directly with temperature. As mentioned previously with regard to roosting habits, Micropteropus and Epomops roosted singly and in clumps of leaves or dense foliage. The wings were wrapped around the body and little movement was observed during the day by these bats. On the other hand, Eidolon roosted in large colonies and moved about almost constantly during the day. It was noticed that the positions of these bats in the roosts were correlated with temperatures and exposures to the sun. For example, early in the day the animals were clustered either below or on top of the terminal parts of fronds and branches, but by midday the bats were congregated beneath the foliage near the centres of the crowns of roost trees. Bats with wings partly extended, as well as wing fanning, were observed frequently during the warmest parts of the

ECOLOGY O F THREE PTEROPIDS 367

day. Similar behavioural responses to warm temperatures were reported for Australian pteropids by Robinson & Morrison (1957).

The behavioural thermoregulation observed was correlated to the homeothermy ex- hibited by the bats studied (Figs 4 to 6). When tested in low ambient temperatures, the smallest bats seemed more homeothermic than the largest animals. On the basis of the behavioural activities observed that were apparently associated with responses to tempera- tures, the variable responses to low temperatures exhibited by the bats tested probably reflected the methods of testing by restraining the animals, as well as the physiological states and thermoregulatory abilities of these pteropids.

Associations with other bats The three species of pteropids compared herein were associated ecologically mostly with

each other, as well as Myonycteris torquata and Hypsignathus rnonstrosus. These five species either were found roosting in the same vicinity or were netted at the same place in littoral vegetation along the coast in Rio Muni (Jones, 1971). Nycteris hispida was collected occasionally at the locality where Eidolon, Epornops, and Micropteropus were obtained. However, N . hispida was taken only from inside a building and was not netted as were the pteropids. On one occasion, an Epomops was taken with several Megaloglossus woerrnanni in a mist net set beneath the roof of an old building in the interior of Rio Muni. For a discussion of the relationships of these pteropids with other bats in the Congo, see Allen, Lang & Chapin (1917). For some comparisons of associations between sympatric species of Neotropical bats, see Hooper & Brown (1968) and Brown (1968).

Predators Predation on bats was noted infrequently in Rio Muni. On 18 April 1968, a Pcrodicticus

potto was observed eating Eidolon where this species fed on breadfruit (Jones, 1969). Rosevear (1965) listed several carnivores that might be attracted to colonies of Eidolon, but he found no recorded evidence of predation on this species. Eidolon was preyed upon occasionally by humans for food; these bats were seen for sale several times in the market in Bata, Rio Muni. Predation on Eidolon by birds and humans was mentioned by Ogilvie & Ogilvie (1964). The importance of large bats in human diets was summarized briefly by Brosset (1966b).

Summary Relative abundance of the bats studied was concordant with seasonal rainfall and corres-

ponding availability of food materials. Epornops and Micropteropus were present in thc area studied throughout most of the year, but Eidolon was abundant for only about three months.

No fixed breeding seasons were noted for Epomops and Micropteropus ; Eidolon produced young from October to February and mated after the rainy season. Peaks in reproductive activities of males occurred during the season when the bats studied were most abundant in the study area.

Although all three pteropids were found occasionally in the same trees, there were no overlaps with regard to the locations of the roosting bats. Eidolon roosted in colonies in the tops of tall trees. Epornops roosted singly and usually in clusters of leaves 4 to 6 m from the ground. Micropteropus roosted singly in dense foliage near the bottom of trees or in small trees and shrubs.

368 C . JONES

In the area studied, wild pteropids fed mostly on fruits of cultivated plants. Eidolon consumed large fruits mostly from the ends of branches near the tops of trees. Epomops ate fruits that grew in foliated parts of trees. Captive Micropteropus and Epomops sucked fluids from foods and discarded pulp materials more than Eidolon. Wild Epomops fed mostly on the fleshy coverings of fruits; Eidolon consumed the insides of fruits.

There were differences in levels of flight between the species, as revealed by heights at which bats were captured in mist nets set at variable heights up to 6 m above the ground. Eidolon was captured only at the upper levels, Micropteropus was taken mostly near the ground, and Epomops was netted at both levels, but mostly at the upper level. Differences in levels of flight corresponded to various levels of roosting and feeding that were deter- mined for each species.

Differences in flight were noted between the species studied. These differences ranged from slow, regular flight of Eidolon to rapid, agile flight of Micropteropus. Epomops seemed intermediate to the other genera in habits of flight. The differences in flight were correlated directly with variations between the species in certain morphological features and corres- ponding aerodynamic properties associated with flight.

Thermal responses varied between the pteropids tested. Under normal conditions, body temperatures of captive Micropteropus were generally closer to ambient temperatures than body temperatures of the other forms. In low ambient temperatures, Micropteropus exhibited greater homeothermic tendencies than either Epomops or Eidolon. Responses to decreased ambient temperatures seemingly were correlated with differences between the genera with regard to apparent behavioural thermoregulation. Eidolon exhibited more activities during the day that were correlated directly with temperature than Epomops and Microp teropus.

There were differences between the species with regard to foods and certain habits of feeding. The data on foods eaten by wild Micropteropus were insufficient for making com- parisons with the information obtained for the other species. In the area studied, wild pteropids fed mostly on fruits of cultivated plants. Eidolon consumed large fruits mostly from the ends of branches near the tops of trees. Epomops ate fruits that grew in foliated parts of trees. The latter species carried fruits away from the trees of origin, but the former species did not carry food from the tree where the animals fed. Captive Micropteropus and Epomops sucked fluids from foods and discarded pulp materials more than Eidolon. This behaviour probably reflected differences between these species with regard to the parts of fruits eaten commonly. Wild Epomops fed on the fleshy coverings of fruits; Eidolon con- sumed the inside of fruits.

In Rio Muni, E. helvum, E. franqueti, and M . pusillus occurred in geographic sympatry and utilized many of the same parts of the habitats. In addition, the species studied shared many biological attributes as expected for similar forms within a systematic category. However, complete ecologic overlaps did not occur because of differences between the forms studied in several biological attributes. The aforementioned differences in certain mor- phologic features, habits, and stratifications probably reflected strong niche specializations of the forms studied. These biological stratagems and specializations seemingly were means of effecting ecological separation and reducing competition between these sympatric species.

Assistance in the collection of specimens was provided by Jorge Sabater Pi, Frances Miller Cashner and Craig Jones. Gordon Corbet and John Hill of the British Museum (Natural History)

E C O L O G Y O F T H R E E P T E R O P I D S 369

and Karl Koopman of the American Museum of Natural History allowed me to study materials in collections under their care. Information on bats was provided by James S. Findley and Henry W. Setzer. Figures were drawn by Wilma Martin. Constructive comments on the manu- script were made by Terry Vaughan, Richard Banks, Don Wilson, and Richard Manville. Field studies in Rio Muni were supported by the National Geographic Society and the National Institute of Health (FROO164).

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