Tropical Bats Research Articles

Seasonal Fat Reserves of Bats in Two Tropical Environments

Seasonal fat deposits were examined in eight species of bats from two localities in Jamaica. All species, except the nectarivore Monophyllus redmani, have a significant decrease in fat reserves during the dry season. In insectivorous bats, ♀ ♀ generally have more fat than ♂ ♂ during periods of maximal fat reserves; this difference normally disappears during the dry season. Bats with other food habits show no sexual dimorphism in fat deposition and appear to have smaller annual variations in the size of fat reserves. These data are compatible with the interpretation that insectivorous species face the greatest seasonal variation in food availability, which is derived from studies of the metabolism, temperature regulation, and reproduction of tropical bats. It is suggested that the tropical bats most likely to invade a temperate environment ate those whose habits expose them to the most seasonal food supplies.

The Structure of Bat Communities

Multivariate morphometric analysis of faunas may provide a useful estimate of ecologic structure. Tropical bat faunas resemble one another in faunal statistics despite trenchant taxonomic differences, suggesting common evolutionary pressures in three tropical regions. Each fauna consists of many similar closely packed, overlapping, relatively invariable species and a few distinctive, distant, isolated, variable kinds. Temperate and tropical faunas differ in the greater rarity, or even absence, of highly distinctive taxa in the former but are not meaningfully different in packing or degree of overlap.

Foraging Patterns and Resource Utilization in Seven Species of Bats in a Seasonal Tropical Forest

Many tropical bats eat fruit, nectar, and pollen, and many tropical plants are pollinated or dispersed by bats. These groups make up a coevolved system that illustrates the effects plants can have on animal populations, and conversely, the effects animals can have on plant populations. This paper reports a 2—yr intensivie study of one bat—plant community in a seasonal Costa Rican forest. Seven common phyllostomatid bat species visited flowers or fruits. These were Glossophaga soricina, Phyllostomus discolor, Artibeus jamaicensis, Artibeus lituratus, Sturnira lilium, and Carollia perspecillata. The incidence of nectar ivory was high among these species, even among the species previously considered to be frugivores. Flora resources were seasonally abundant and competition for these resources appeared minimal during the period of peak abundance, but only G. ssoricina was nectarivorous during the period of low flower abundance. Fruit resources were more evenly available through the year and were more finely divided among the species of bats. There was a correlation between size of bat and the average size of fruits eaten. To the extent that competition for food has influenced the structure of this bat community, competition for fruits was more important than competition for nectar and pollen in determining species diversity. Resource distributions through space and time also infuenced bat foraging and reproductive behaviors. Small species of bats feed on resources of high abundance, whereas large species utilize resources that are patchy in time and space. The latter species probably forage in groups to maximize foraging efficiency. Reproductive behavior is seasonal and correlated with resource abundance. The flowering periods of plant species tend to be displaced, suggesting competition among plants for bat—pollinator services. A combination of the timing of plant—reproductive behavior and bat foraging characteristics promotes long—distance outcrossing and seed dispersal. These are critical factors in determining the low—density propulations characteristic of many tropical plant species.

The breeding pattern of the eastern epauletted bat, Epomophorus anurus Heuglin, in Uganda.

Summary. Continuous monthly observations of the reproductive organs of the Eastern epauletted bat, Epomophorus anurus, has revealed its breeding to be cyclic with two distinct breeding seasons separated by about a month. Gestation appeared to last between 5 to 6 months, and occurred from April to September and October to March. Testes were heaviest from February to April and from September to December, and a majority of young bats were caught in late March and early October during the short intervals between breeding. This study supports the findings of earlier workers showing that breeding in tropical fruit bats is seasonal and closely related to rainfall. It further supports an earlier suggestion that this fruit bat is polyoestrous and breeds continuously.

Temperature Regulation in Three Species of Tropical Bats

Temperature Regulation in Three Species of Tropical Bats

An Experimental Study on the Relation of Mortality of Young to Adult Numbers in Colonies of the Lesser Sac-Winged Bat, Saccopteryx bilineata perspicillifer

The mortality of young bats due to falls in colonies of the tropical insectivorous bat, SaccoPteryx bilineata perspicillifer (lesser sacwinged bat), a species that roosts in tree cavities in tropical rain forests, can be experimentally reduced by the installation of low artificial ceilings into roosts. When this is done over successive breeding periods, the resulting adult colonies are significantly larger than colonies in which the ceilings were not introduced. Mortality of young bats within roosts may act as a means of regulating colony size.

The Structure of Tropical Bat Faunas

The species that constitute a tropical bat fauna partition the food available in an environment in an orderly manner, the two most important parameters of partitioning being the type of food and food particle size. On small Caribbean islands there seems to be a fundamental partitioning of food that includes one fruit bat, two nectar bats, two insect bats, and one fishing bat; other food habits, such as blood and meat, are not generally present because of the apparent absence of these foods in sufficient quantities. Mainland tropical bat faunas are similarly structured in terms of food type and size, but it is not possible to make a complete analysis due to the many rare species, whose habits are generally unknown.

TEMPERATURE REGULATION AND CAVE-DWELLING IN BATS : AN EVOLUTIONARY PERSPECTIVE

1. Bats are placed in three groupings on the basis of their thermoregulatory mode. Group 1 includes species that enter torpor readily at low ambient temperatures and, in general, appear to be incapable of sustaining a body temperature much in excess of ambient if they are inactive for a prolonged period of time. Group 2 includes species that are able to voluntarily enter torpor but are also able to maintain high body temperature when inactive at quite low ambient temperature. Group 3 includes species that do not voluntarily enter torpor and may, in fact, regulate body temperature precisely over a range of activity states. It is recognised that this classification is not rigorous. 2. It is predicted that Group 1 bats will not be significantly represented in caves except at high latitudes where they will use them as hibernacula, that Group 2 bats will be the predominant cave-dwelling forms of the middle latitudes and that Group 3 bats will be well represented in low latitude caves but, primarily for reasons of food supply, will be excluded from caves at other latitudes. These predictions are, in general, satisfied by present knowledge of distribution patterns. 3. An hypothesis is proposed in which the evolution of thermoregulation in bats passed through the stages Group 1 to Group 3. Torpor, as it is manifest in modern representative of Group 1, is not seen as a « primitive » attribute of bats but nor is it considered that Group 1 bats ever passed through a phase of « complete » homeothermism. It is suggested that the necessity to partition roosting sites and, more importantly, the competitive partitioning of food resources as bat diversity increased may have, at first in part and finally in total, released many tropical bats from the need for torpor. NcNab’s view of torpor as adaptive to periods of food scarcity is accepted in this paper. 4. The capacity for torpor as expressed in tropical Group 1 or Group 2 species is seen as having been preadaptive to the environments of higher latitudes. Variants upon thermoregulatory modes have appeared in temperate latitude species, including increased tolerance of low ambient temperature, a seasonal change in the expression of torpor, and, particularly, a repertoire of physiological and neural mechanisms appropriate to hibernation. 5. The relevance of a capacity for torpor to cave-dwelling is not evidenced until the middle or high latitudes. Given that the species can echolocate, cavedwelling can only emerge if the bat is preadapted in its thermoregulatory mode to the particular characteristics of the cave environment at any given latitude range. The cave environment has not played a significant role in the evolution of thermoregulation in bats. 6. In bats torpor is manifest most clearly in the phyllogenetically advanced groups and « complete » homeothermy is most evidenced in the phyllogenetically more conservative groups. It is suggested that the mainstream of microchiropteran evolution was in the direction of perfection of flight and foraging upon insects, that the propensity for torpor was never lost from this mainstream, hut that all the shifts away from this mainstream were such as to release hats, in part or whole, from the need for torpor and hence promoted a shift to Group 2 or Group 3 status.

Survival of spermatozoa in the female genital tract of the Indian vespertilionid bat,Pipistrellus ceylonicus chrysothrix (wroughton)

1. Inseminated females specimens of the tropical vespertilionid bat,Pipistrellus ceylonicus chrysothrix, were kept isolated from the males for varying lengths of time during the months of June and July in 1968 and 1969.

Hematological data from tropical American bats.

Hematological values and diameters of erythrocytes are reported for bats from Colombia, Puerto Rico, and St. Croix. A marked variation was observed in most of the blood characters considered. Smaller bodied species had lower leucocyte counts than larger ones, as did non-gravid females and adult males when compared with pregnant and lactating females. Erythrocyte counts of frugivorous species were lower than those reported for insectivorous bats. Mean erythrocyte diameters were similar and had comparable ranges of variation. There were no significant differences between lactating, gravid, or non-gravid females in hemoglobin concentration, hematocrits, differential counts, or diameter of erythrocytes. Certain abnormalities in the blood picture were observed, and data are discussed in comparison with those obtained by others.

Reproductive cycle of a neotropical insectivorous bat, Myotis nigricans.

REPRODUCTIVE patterns in bats fall into three main categories. A synchronous breeding season and monoestry is common in all holarctic bats1. Continual asynchronous breeding is found in some tropical bats of the families Desmodontidae2, Phyllostomatidae3, Pteropodidae, Emballonuridae and Molossidae4. In some palaeotropical bats seasonal polyoestry is the rule, with two synchronized breeding seasons each year4,5.

The economics of temperature regulation in neutropical bats

1. 1. The level and effectiveness of thermoregulation in bats is determined by the interaction of weight, basal rate of metabolism and thermal conductance. 2. 2. Conductances in tropical bats are greater than expected from weight. 3. 3. Basal rates of metabolism are higher than expected by weight in nectar-, fruit- and meat-eating bats, lower than expected in insectivorous species and intermediate in vampires, this correlation depending upon the seasonal stability of food resources in the environment. 4. 4. Therefore, nectar-, fruit- and meat-eating bats are effective thermoregulators, vampires are marginal regulators and insectivorous species readily enter torpor. 5. 5. Torpor evolved in the tropics in response to the high cost of thermoregulation at a small weight.

Oxygen consumption, temperature, and water loss in bats from different environments.

Oxygen consumption, temperature, and water loss in bats from different environments.

The Male Reproductive Cycle of the Bat Artibeus lituratus

Reproductive activity of males of the tropical frugivorous bat, Artibeus lituratus, was investigated in west central Colombia for a 17-month period during 1961-1963. The climate of the area varied little throughout the study period, and climatic conditions did not influence reproductive activity in males. Data based on presence of sperm, length and tubule diameter of the testis and diameter of the epididymis indicate that males are capable of reproductive activity at any time of the year, and the reproductive pattern is acyclic without suggestions of seasonal variations.

The Histology of the Chest Gland of the Pale Spear-Nosed Bat

The chest gland of the tropical American bat Phyllostomus discolor is present and functional in males and vestigial in females. It is a large, sebaceous holocrine gland of the simple type. The secretion causes a strong odor which probably serves as a means of recognition and aids in the location of the daytime roost of the colony.

Bat longevity and metabolic rate

Rubner's hypothesis that metabolic rate is a major factor in determining longevity was considered by comparing data on temperate and tropical bats. Body temperatures and metabolic data indicate considerably higher energy expenditure for tropical species. A review of longevity records and population survival rates suggests that bats as a whole have long life spans. The present records are a function of banding effort and an increasing number of old bats are being recovered in tropical species. An examination of reproductive capacity shows most species, whether temperate or tropical, have only one reproductive period per year when the female gives birth to one young. There is no evidence of a higher reproductive rate in tropical forms which might be expected if they had a higher mortility rate than temperate species. Thus, in spite of the fact that the metabolic rates of tropical species are higher than their temperate counterparts, warm climate forms do not appear to have a shorter maximum life span.

Reproductive Cycle of the Big Fruit-eating Bat, Artibeus lituratus Olfers

IN tropical America no order of mammals is represented by such a diversity of forms and abundance of individuals as the bats (Chiroptera); but in this region the reproductive habits of only a few species have been investigated. Tropical American bats in which the reproductive cycles are known fall into one of two groups: (1) those with the typical mammalian reproductive pattern of restricted sexual seasons and coincidence of copulation; (2) those with no well-defined sexual season and which breed throughout the year. The first group is represented by only one species, the phyllostomid bat, Glossophaga soricina, examined by Hamlett1 in Brazil, and it is doubtfully placed in this category, since the reproductive pattern was deduced from an investigation of relatively few specimens taken at only one time of the year. In the second group, again only one species can be included, the economically important vampire bat, Desmodus rotundus murinus, which was examined in Panama by Wimsatt and Trapido2. We have ourselves3 presented Colombian records which indicate thafc at least some tropical, equatorial phyllostomid bats, unlike North American forms, are polyœstrous and breed throughout the year, but our results were limited and based only on females.

Variation in the Os Penis of Tropical Fruit Bats

Variation in the Os Penis of Tropical Fruit Bats

Histological and histochemical observations on the parotid, submaxillary and sublingual glands of the tropical American fruit bat Artibeus jamaicensis Leach

Histological and histochemical observations on the parotid, submaxillary and sublingual glands of the tropical American fruit bat <i>Artibeus jamaicensis</i> Leach

Observations on the Life Histories of Panama Bats

Since there is only scanty information on the breeding, feeding, habits, and habitats of all but a few species of tropical bats, the following observations made between February 10 and August 15, 1953, in the region of the Panama Canal Zone, are presented. During the first half of this period, as assistant to Dr. D. R. Griffin, I collected alive as many species of bats as possible for the primary purpose of making recordings of their high-frequency sounds used in echolocation. This work was supported by a contract between The Office of Naval Research and Cornell University. In the course of this work I visited many bat roosts, observed various species both in the field and laboratory, and prepared specimens, some of which are now in the Museum of Vertebrate Zoology. During the last four months of the period I remained in the region studying the fishing habits of Noctilio leporinus and did more incidental collecting of other species. I am indebted to Dr. Harold Trapido for pointing out bat roosts in the vicinity, and to Dr. Herbert C. Clark, Director of the Gorgas Memorial Laboratory, for allowing me to use the Juan Mina field station, five miles northeast of Gamboa, as a base of operations during parts of April, May, and August. For accounts of the already existing knowledge of the species listed below see Goldman (Smithsonian Misc. Coll., 69, No. 5, 1920), Enders (Bul. Mus. Comp. Zool., Harvard, 78, No. 4, 1935), and Allen (bats, Harvard Univ. Press, 1939). Goldman gives a good description of the climate, topography, and vegetation of Panama. Most locality names can be found on any map of the Canal Zone Region. Rhynchonycteris naso (Maximilian).—Seven were caught in trammel nets at Borinquen Dam, two miles northwest of Pedro Miguel, on Borinquen Highway, between 6:15 …