Bat Assemblages Research Articles

Species composition, abundance and vertical stratification of a bat community (Megachiroptera: Pteropodidae) in a West African rain forest

A pteropodid bat community was surveyed in a West African rain forest using mist-nets set for 3 mo in 2 consecutive years (1996-97). The captures were carried out in the understorey and in the canopy for a total of 5054 mist-net hours and were analysed to answer three main questions: (1) to what extent does the bat assemblage vary along the vertical axis, (2) does the observed vertical stratification depend on wingspan (with largest bats preferring canopy openings to the cluttered understorey) and (3) was the vertical stratification repeatable from one year to the next? Nine bat species were reported, among which two were captured exclusively in the canopy where the total capture rate tended to be higher. The community structure did not differ between the four canopy stations. Four species significantly favoured canopy, two significantly favoured understorey and two were opportunistic regarding vertical stratification. Wing size and canopy-preference index were not significantly correlated and except for Eidolon helvum, index values for the 2 sampling years were correlated. Important inter-annual and seasonal variations of species richness and capture rate were observed and these are discussed in relation to rainfall patterns and migratory behaviour of the species concerned.

Ecological zoogeography of the bats of Paraguay

AbstractAim To relate the composition of bat assemblages in Paraguay to environmental factors (vegetation) and to test the hypothesis that the observed patterns of distribution of Paraguayan mammals is ultimately due to soils and geological features.Location Paraguay.Methods Museum specimens were used to create a data base of 3762 individuals of forty‐eight species collected in twenty‐six 50 × 50 km sites distributed throughout the country. Proportion of each of sixteen vegetation types per site was estimated from vegetation maps. Vegetation and bat data were related using canonical correspondence analysis (CCA) and Mantel tests. The same analyses were performed with the bat data grouped in terms of trophic strategies.Results A significant relationship was found between composition of vegetation and composition of bat assemblages. CCA ordination arranged plant associations and bat assemblages into three distinct groups: Dry Chaco, Floodable Lands and Eastern Paraguay, which correspond to the major characteristics of the Paraguayan vegetation, geology and soils. Frugivorous bats were restricted to Eastern Paraguay and Floodable Lands, whereas most insectivore and omnivore species occur across the entire country. However, the maximum abundance of insectivorous and omnivorous species within each genus indicates that there is at least a partial segregation of species to one of the three regions, and in those cases where the maximum abundance of congeneric species coincide, those species differ considerably in size.Main conclusions The Paraguayan bat fauna is a composite of species from various South American biomes, with no endemic species. However, species are not randomly distributed across the country despite the lack of geographical barriers and the high dispersal capabilities of bats. Instead, species presence at any given site is strongly associated with vegetation patterns that are ultimately the result of the geological history of the area. This correlation can be explained partially in terms of habitat suitability and resource availability. Additionally, results suggest that interspecific interactions are also an important component in determining the composition of a given bat assemblage.

Consistency and variation in the bat assemblages inhabiting two forest islands within a neotropical savanna in Bolivia

Neotropical bats occupy a large variety of trophic niches, and represent locally abundant, species-rich communities. As such, they are highly suited as a model group for the study of temporal and spatial dynamics of animal communities. However, despite this important research potential, data on the dynamics and turnover rates of Neotropical bat communities are lacking. We here study both aspects for bats inhabiting two natural forests surrounded by savanna in Bolivia. Over a period of 8 y, both bat communities showed high rates of species turnover. As predicted, species relying on fluctuating food resources were more likely to be absent in particular years, whereas species relying on more predictable food supplies were present in all years.

Structure of a bat assemblage (Mammalia, Chiroptera) in Serra do Caraça Reserve, South-east Brazil

The Serra do Caraca Reserve is situated in the southern portion of the Espinhaco Mountain Range, and contains areas of campos de altitude, cerrado and atlantic forest. This study had as its objective the registering of the bats species that occur in the reserve. The data collection was carried out in one year through monthly samplings, using mist nets set on trails, and also through hand capture. A total of 246 individuals were collected (0.72 bats/net-hour), distributed across 15 species, belonging to the families Phyllostomidae (83.0%; nine species), Vespertilionidae (12.5%; three species) and Molossidae (4.5%; three species). The most abundant species were Sturnira lilium (E. Geoffroy, 1810) (n = 121, 60.5%), Myotis nigricans (Schinz, 1821) (n = 21, 10.5%) and Platyrrhinus lineatus (E. Geoffroy, 1810) (n = 10, 5.0%), and less represented were Lasiurus blossevilli (Lesson y Garnot, 1826) (n = 2, 1.0%), Eumops perotis (Schinz, 1821) (n = 2, 1.0%) e Vampyressa pusilla (Wagner, 1843) (n = 1, 0.5%). The richness of species found and the non-occurrence of phyllostomines in the reserve could be indicative of some level of forest disturbance.

A Conservation Assessment of the Bats of the Simandou Range, Guinea, with the First Record ofMyotis welwitschii(Gray, 1866) from West Africa

We report on the results of a bat survey of the Pic de Fon, Simandou Range, southeastern Guinea. This bat survey was part of a larger Rapid Assessment Program (RAP) study conducted by Conservation International in an area currently explored for iron-ore mining by an international company. We document a speciose bat assemblage characterised by forest species, including bats such as Epomops buettikoferi, Rhinolophus guineensis and Hipposideros jonesi that are endemic to Upper Guinea or West Africa. The sympatric occurence of three species of Kerivoula is noteworthy, with K. phalaena representing the first record for Guinea. Moreover, three individuals of Welwitsch's mouse-eared bat, Myotis welwitschii, were captured during the survey. This is the first record for West Africa and represents a range extension of minimally 3,400 km to the northwest from the nearest known localities. We review the distribution of this species in Africa and conclude that the species shows a paramontane distribution pattern (sensu Koopman, 1983). We also report M. welwitschii for the first time from Burundi. Our results of the RAP survey as well as the occurrence of bat species that are endemic to the Upper Guinea Highlands highlight the outstanding regional importance of the montane habitats of West Africa in general, and of the Simandou Range in particular for the conservation of bats in Africa.

Calcium as a limiting resource to insectivorous bats: can water holes provide a supplemental mineral source?

Data are presented on a bat assemblage captured among 10 water holes in Colorado over 5 years. The assemblage consists of Myotis ciliolabrum, M. evotis, M. lucifugus, M. thysanodes, M. volans, Eptesicus fuscus, Lasiurus cinereus, Lasionycteris noctivagans and Corynorhinus townsendii. Results show that reproductive females and juveniles are captured in higher frequencies at water holes containing higher water hardness and that water hardness correlates highly significantly with dissolved calcium content. Also presented are laboratory test data on the stomach volume of Eptesicus fuscus that provide a model for understanding the effect of dissolved calcium content in water as a significant resource. These data indicate that water holes provide supplemental sources of calcium for bats not provided by diet.

A Biodiversity Assessment of Bats (Chiroptera) in a Tropical Lowland Rainforest of Central Amazonia, Including Methodological and Conservation Considerations

In our study of bat diversity in the Amazon Basin, we captured bats in undisturbed continuous forest and in forest fragments at the Biological Dynamics of Forest Fragments Project (BDFFP) near Manaus, Brazil, from January 1996 until July 1999. We recorded 72 species of bats in a sample of more than 7700 individuals caught during 29,900 mistnet hours in terra-firme forest. Species accumulation curves and mathematical estimates of species numbers based on the number of species captured with standardized methodology suggest that we sampled about 95% of the entire expected bat fauna of the area, including aerial insectivorous bats. Our results are similar to those of other mistnetting inventories of Amazonian bat assemblages in terms of species composition and number of species per bat family. Some species considered widespread in Central Amazonia and expected at our study site were not recorded. We interpret their absence as effects of sampling bias and of local ecological conditions. We know from acoustic monitoring (i.e., identification of bats by their echolocation calls) that our mistnet data are incomplete for aerial insectivorous species. We conclude that the development of comprehensive inventories of key vertebrate taxa such as bats derived from a combination of several standardized sampling procedures is essential to develop meaningful, conservation-oriented plans for land-use and management of protected areas. Resumo Em nosso estudo sobre diversidade de morcegos na Bacia Amazônica, nós capturamos morcegos em floresta contínua não perturbada e em fragmentos florestais no Projeto Dinâmica Biológica de Fragmentos Florestais (PDBFF), próximo à Manaus, Brazil, de Janeiro de 1996 até Julho de 1999. Nós registramos 72 espécies de morcegos capturando cerca de 7700 indivíduos em 29,900 horas de captura em áreas de terra-firme. As curvas de acumulação e modelos matemáticos baseados no número de espécies capturadas com metodologia estandartizada indicam que nós registramos cerca de 95% da fauna esperada para a área, incluindo as capturas de espécies de morcegos aéreos insetívoros. Nossos resultados são equivalentes a outros inventários baseados em redes de captura de morcegos na Amazônia, em termos de composição de espécies e em número de espécies para cada família de morcegos. Algumas espécies consideradas como uniformemente distribuídas na região Amazônica e que deveriam também ocorrer na nossa área de estudo não foram coletadas. Nós interpretamos a ausência de espécies esperadas como um efeito de limitações na metodologia e devido a condições ecológicas locais. Sabemos por monitoramento acústico (identificação de morcegos através dos sinais de ecolocação), que nossos dados de redes de captura estão incompletos para morcegos insetívoros aéreos. Nós concluímos que o desenvolvimento de inventários de grupos chave, como morcegos, com a combinação de vários métodos de amostragem estandardizados é essencial para o desenvolvimento de planos conservationistas significativos no uso da terra e no controle de áreas protegidas.

Species richness in an insectivorous bat assemblage from Malaysia

Estimates of insectivorous bat diversity in the Palaeotropics have largely been hampered by the lack of long-term studies employing appropriate capture techniques. Using a variety of trapping methods, 45 insectivorous bat species were captured in approximately 3 km2 of primary dipterocarp rain forest in Malaysia over 8 y. The cumulative site list for Kuala Lompat Research Station, Krau Wildlife Reserve, now stands at 51 insectivorous species. Although this is likely still not a complete list, it is already one of the most species-rich in the world. We attribute much of our success in recording this diversity to the extensive use of harp traps. Of the 45 species, 38 were captured in an intensive harp-trapping programme (> 1030 harp-trap nights) of the forest interior (22 species exclusively so). Insectivorous bats of the forest interior are thus a key component of Old World bat diversity, particularly in South-East Asia, and are dominated by taxa capable of detecting and capturing prey in cluttered environments (Hipposideridae, Rhinolophidae, Kerivoulinae and Murininae).

Species composition and reproductive phenology of bats in a tropical landscape at Los Tuxtlas, Mexico

The structure, composition and reproductive phenology of a bat assemblage were investigated in the tropical region of Los Tuxtlas, Mexico. A 90-km2 landscape, originally occupied by rain forest, consisted of forest fragments and natural corridors of vegetation surrounded by pasturelands. Artificial strips of vegetation also were present as live fences. Bats were sampled with mist nets set at ground level in 52 forest fragments, three corridors, nine shaded plantations, six unshaded plantations and three live fences. We sampled each site twice, each time for a 5-h period for two consecutive nights. Bats were captured and released and the species identity and reproductive condition of adult females were recorded. Annual fruiting phenology and fruit production was measured with fruit traps in a forest site in three 500 × 20-m transects. We captured 4799 bats of 39 species. At forest sites we recorded 97% of the species and captured 44% of the bats. In corridors we captured 76% of the species and 16% of the total individuals. In the plantations we captured 71% of the species and 32% of the individuals. In the live fences we captured 32% of the species and 8% of the individuals. Three species, Pteronotus parnelli, Carollia brevicauda and Glossophaga soricina, accounted for 52% of all bat captures. Fruit-eating species and fruit-eating insectivores accounted for 65% of captures. Fleshy fruits were available year-round, but a seasonal pattern was evident. Presence of lactating females seemed to be associated, in general, with rainfall and fruiting seasonality, but individual species displayed different patterns ranging from aseasonal polyoestry to seasonal bimodal polyoestry, seasonal polyoestry and seasonal monoestry. Despite extensive fragmentation of the original rain forest, a species-rich bat assemblage still exists in the landscape studied. Short distances among remaining forest fragments and man-made habitats seem to facilitate persistence and reproductive connectivity among members of this bat assemblage.

COMPOSITION AND STRUCTURE OF BAT ASSEMBLAGES IN PARAGUAY: A SUBTROPICAL–TEMPERATE INTERFACE

Little is known about geographic variation in the local composition of South American assemblages of mammals or the factors that may produce such variation. This is particularly unfortunate in Paraguay because it occurs at the interface of a number of phytogeographic regions (e.g., Cerrado, Chaco, Interior Atlantic Rainforest, and Pantanal) and is the point at which many temperate species reach their northern limits or at which tropical species reach their southern limits. Based on 2 years of intensive fieldwork, we documented the species and familial composition of bat assemblages at 25 sites throughout the country. We also estimated similarity among sites based on indices sensitive to presence or absence of species (Ochiai's index), to rank abundance of species (rank correlation index), or to relative abundance of species (Euclidean index). Geographic distance between sites accounted for little variation in composition based on presence-absence or rank abundances of species but accounted significantly for variation related to both identity and relative frequency of species. Distinct assemblages of species do not correspond to the 7 distinct biomes of the country; rather, strong differences exist between sites east (mesic) and west (xeric) of the Rio Paraguay. For the most part, these differences are related to dominance by molossids (e.g., Eumops patagonicus, Molossops temminckii, and Molossus molossus) and vespertilionids (e.g., Lasiurus ega, Myotis albescens, and M. nigricans) in dry regions versus phyllostomids (e.g., Artibeus fimbriatus, A. lituratus, and Sturnira lilium) in mesic regions. As a consequence, classification of sites into 2 broad biogeographic regions based on bat familial composition generally is concordant with that based on plants.

A Comparison of the Phyllostomid Bat Assemblages in Undisturbed Neotropical Forest and in Forest Fragments of a Slash‐and‐Burn Farming Mosaic in Petén, Guatemala1

ABSTRACTUsing mist nets, we compared phyllostomid bat ensembles of continuous mature forest in Tikal National Park, Guatemala, and of forest fragments in the nearby farming landscape. Of 20 species captured, 13 were shared between treatments, 4 were unique to continuous forest, and 3 were unique to forest fragments. Dominance–diversity curves were similar for the two treatments except that Sturnira lilium comprised 43 percent of captures in the forest fragments, resulting in greater dominance there. Capture rates (and presumably relative abundance) differed significantly between continuous forest and forest fragments, both in terms of species and feeding guilds. Sturnia lilium and Dermanura sp. were captured significantly more often in forest fragments than in continuous forest, whereas Artibeus jamaicensis, A. lituratus, and Centurio senex were taken significantly more often in continuous forest. Large frugivores accounted for a higher proportion of total captures in continuous forest than in forest fragments, whereas small frugivores showed the opposite pattern. By their abundances, Carollia perspicillata and S. lilium are indicators of forest disturbance. The relative abundances of large frugivores, which feed on large fruits of mature forest trees, and small frugivores, which feed on small‐fruited plants occurring in early succession, are an indicator of forest disturbance. Other groups, such as large insect‐ and vertebrate‐eating bats, because of their low capture rates, are impractical as indicators for rapid assessment of forest disturbance based on mist netting, but may prove especially vulnerable to forest fragmentation.

A Comparison of the Phyllostomid Bat Assemblages in Undisturbed Neotropical Forest and in Forest Fragments of a Slash-and-Burn Farming Mosaic in Petén, Guatemala1

Using mist nets, we compared phyllostomid bat ensembles of continuous mature forest in Tikal National Park, Guatemala, and of forest fragments in the nearby farming landscape. Of 20 species captured, 13 were shared between treatments, 4 were unique to continuous forest, and 3 were unique to forest fragments. Dominance–diversity curves were similar for the two treatments except that Sturnira lilium comprised 43 percent of captures in the forest fragments, resulting in greater dominance there. Capture rates (and presumably relative abundance) differed significantly between continuous forest and forest fragments, both in terms of species and feeding guilds. Sturnia lilium and Dermanura sp. were captured significantly more often in forest fragments than in continuous forest, whereas Artibeus jamaicensis, A. lituratus, and Centurio senex were taken significantly more often in continuous forest. Large frugivores accounted for a higher proportion of total captures in continuous forest than in forest fragments, whereas small frugivores showed the opposite pattern. By their abundances, Carollia perspicillata and S. lilium are indicators of forest disturbance. The relative abundances of large frugivores, which feed on large fruits of mature forest trees, and small frugivores, which feed on small-fruited plants occurring in early succession, are an indicator of forest disturbance. Other groups, such as large insect- and vertebrate-eating bats, because of their low capture rates, are impractical as indicators for rapid assessment of forest disturbance based on mist netting, but may prove especially vulnerable to forest fragmentation.

A long‐term ecological survey of bats (Mammalia, Chiroptera) in the Eastern Niger Delta (Nigeria)

The structure of bat assemblages was studied in relation to variation in forest landscapes in four localities of the eastern Niger Delta (southern Nigeria). The study areas were inhabited by thirteen species, seven Megachiroptera and six Microchiroptera, among which Eidolon helvum, Hypsignathus monstrosus, Rousettus egyptiacus, Saccolaimus peli, and Hipposideros caffer were recorded for the first time, whereas Epomophorus gambianus, Scotonycteris zenkeri, Megaloglossus woermanni, Scotophilus viridis, and Mops thersites were first cited only recently. The majority of captures occurred in secondary forest habitat (99 specimens belonging to 10 species), followed by primary forest (40 specimens, 5 species), and by the bush (13 specimens, 5 species). A multivariate set of analyses arranged the various species into six ‘ecological groups’: (i) Eidolon helvum, Mops thersites; (ii) Hipposideros caffer, (iii) Hypsignathus monstrosus; (iv) Rousettus egyptiacus, Epomops franqueti, Scotonycteris zenkeri, Nycteris arge, (v) Saccolaimus peli, Scotophilus viridis, Nycteris hispida; (vi) Epomophorus gambianus, Megaloglossus woermanni. The various groups are interpreted in the light of the available information on the ecology and distribution of Nigerian bats.

The Pacific Banyan in the Cook Islands: have its pollination and seed dispersal mutualisms been disrupted, and does it matter?

Fig trees (Ficus spp., Moraceae) are pollinated by species-specific fig wasps and have seeds that are mainly dispersed by fruit bats and birds. Consequently, they should be strongly dependent on mutualisms with animals for their reproductive success. As elsewhere in the Pacific, extinctions of potential seed dispersers have occurred on the islands in the southern Cook Islands archipelago. The abundance of the Pacific Banyan, Ficus prolixa, was found to be unrelated to the extent of potential seed disperser extinctions on different islands. There was no evidence of recruitment on Rarotonga, which has the most diverse bird and bat assemblage, and healthy populations on Mangaia, where all the native avian frugivores are extinct. Despite its very small population sizes on some of the islands, the trees pollinators are still present, showing that this mutualism has not yet been disrupted. Habitat loss, rather than a loss of mutualists, appears to be the main problem facing this species.

Bat assemblages in Tanzanian coastal forests

Des Chiropteres ont ete captures dans 17 petites forets cotieres de Tanzanie, en Afrique de l'Est, entre 1990 et 1992. Quarante-six especes ont ete mises en evidence, avec jusqu'a 15 especes dans une seule foret. Huit ilots forestiers ont ete suffisamment etudies pour que des comparaisons des frequences locales des especes et des indices de diversite puissent etre effectues. L'indice de diversite regional est de 2,74 et les indices locaux se situent entre 1,55 et 1,97. Beaucoup d'especes sont reparties de facon remarquablement irreguliere. Les captures les plus interessantes pour la Tanzanie sont: la confirmation de Myotis tricolor, Tadarida brachyptera, Myonycteris relicta, Rhinolophus deckenii et Kerivoula africana, et les premieres observations de Scotophilus nigrita alvenslebeni, Hipposideros cyclops et Cloeotis percivali.

Bats of a semi-arid environment in south-eastern Australia: biogeography, ecology and conservation

A total of 2075 captures of 11 taxa of bats was recorded during an extensive survey of the vertebrate fauna of the semi-arid Mallee region of Victoria. A further two species, Pteropus scapulatus and Saccolaimus flaviventris, are known from previous records, thus bringing the total to 13 taxa known from the region. There was a marked seasonality in activity patterns and in reproduction. Activity, as revealed by trap captures, peaked over the spring to early autumn months when daytime temperatures are high and nights are mild. Births occurred from October to December, lactating females were recorded from November to February, and juveniles were trapped between December and late February, with minor variation in timing between species. Morphometric measurements revealed that females were generally larger and heavier than males. There was a high level of overlap of species between broad vegetation types. Woodland habitats, especially Riverine Woodland, tended to have a higher frequency of capture and a greater species richness of bats per trapping event than did Mallee Shrubland. The assemblage of bats in the Mallee region, Victoria, like those in other semi-arid regions of southern Australia, includes species that are widespread in Australia (e.g. Chalinolobus gouldii and Nyctophilus geoffroyi), together with species that primarily occur in semi-arid and arid environments (e.g. N. timoriensis, Scotorepens balstoni and Vespadelus baverstocki). This region, which includes mesic riverine habitats, also supports a group of species that are characteristic of temperate south-eastern Australia (e.g. C. morio, V. regulus and V. vulturnus). In comparison with assemblages from temperate and tropical environmental regions, those from the semi-arid region tend to have a lower species richness with fewer families represented, a higher level of insectivory, and a smaller modal body size. The conservation status of bats from the Mallee region, Victoria, is believed to be secure, although the status of N. timoriensis warrants further attention.

Roosting Assemblages of Bats in Arenitic Caves in Remnant Fragments of Atlantic Forest in Southeastern Brazil

Roosting Assemblages of Bats in Arenitic Caves in Remnant Fragments of Atlantic Forest in Southeastern Brazil

The Role of Stochastic and Deterministic Processes in Structuring Neotropical Bat Communities

The extent to which deterministic or stochastic processes affect the composition and morphological structure of communities is an intense debate in evolutionary ecology. For many years, competition was considered to be the dominant deterministic factor that affected structure of animal communities. More specifically, interspecific competition can affect morphological patterns within communities by either size assortment or size adjustment. We investigated the extent to which size assortment could have structured bat assemblages from two well-defined bat communities from northeast Brazil by comparing real ecomorphological characteristics (mean and variance of segment lengths of minimum-spanning trees from principal component scores) to the distribution of like statistics obtained from simulations derived from nested-species pools. Regardless of species pool, the ecomorphological patterns of bat assemblages were no more structured than expected by random selection of taxa from the available species pool. This was true for frugivorous, nectarivorous, and foliage-gleaning insectivorous guilds, and for the phyllostomid community in general, from both Caatinga and edaphic Cerrado biomes. The alternative hypothesis, that coevolutionary processes determine ecomorphological patterns in these neotropical communities, similarly is not supported by our results. The characteristic spatial and temporal heterogeneity of northeast Brazil, combined with the mobile nature of bats, could decrease the intensity, pervasiveness, or predominance of deterministic interactions, thereby leading to an ecomorphological structure indistinguishable from that produced by stochastic processes.

Feeding ecology of Tasmanian bat assemblages

AbstractThe diets of seven of the eight species of insectivorous, vespertilionid bats found in Tasmania were studied in forest areas. The diet of the eighth species, Chalinolobus gouldii, was studied in riparian woodland surrounded by open pasture. Nyctophilus timoriensis was found to be a gleaner with most of its diet consisting of non‐volant insects. Five of the species (Eptesicus vulturnus, Eptesicus regulus, Eptesicus sagittula, Nyctophilus geoffroyi and Chalinolobus morio) fed opportunistically, their diets reflecting local and temporal variations in insect abundance and diversity. Lepidoptera made up most of the diet of these species. The largest species, Falsistrellus tasmaniensis, appeared to be a selective feeder, with Coleoptera being the most important item in its diet. Coleoptera also made up the bulk of the diet of C. gouldii, but caterpillars were also important. For the species studied in forest areas, there was a highly significant correlation between the mean sizes of the lepidopterans (r= 0.95) and coleopterans (r = 0.96) eaten and the size of the bat. For all bats larger than E. sagittula, the mean size of beetles eaten was smaller than the mean size of moths eaten. These results are in accord with expectations from optimal foraging theory.