Emballonurid Bats Research Articles

Divergence times and origin of neotropical sheath-tailed bats (Tribe Diclidurini) in South America

Times of divergence and origin of sheath-tailed bats (family Emballonuridae) in the New World were approximated with a relaxed molecular clock approach using Bayesian analysis of introns from the three nuclear genetic transmission systems in mammals (autosomal, X and Y sex chromosomes). An upper constraint of 30 mya for the oldest known Neotropical emballonurid fossil and a lower constraint of 13 mya for the only pre-Pleistocene fossil of an extant genus were used as calibration points. Differentiation began in the Late Oligocene with the appearance of two subtribes as independently corroborated by each gene. Following an explosive model of evolution, the genera diversified relatively suddenly in the Early Miocene with seven of the eight genera radiating within 1.4 myr and most intrageneric speciation occurring before the Pliocene. Optimization of ancestral areas onto the phylogeny suggests that the ancestor of New World emballonurid bats has its origin in Africa and this is the third report of placental mammals colonizing South America by trans-Atlantic dispersal and subsequent speciation in allopatry.

Echolocation calls in Central American emballonurid bats: signal design and call frequency alternation

AbstractIn southern Central America, 10 species of emballonurid bats occur, which are all aerial insectivores: some hunt flying insects preferably away from vegetation in open space, others hunt in edge space near vegetation and one species forages mainly over water. We present a search call design of each species and link signal structure to foraging habitat. All emballonurid bats use a similar type of echolocation call that consists of a central, narrowband component and one or two short, frequency‐modulated sweeps. All calls are multi‐harmonic, generally with most energy concentrated in the second harmonic. The design of search calls is closely related to habitat type, in particular to distance of clutter. Emballonurid bats foraging in edge space near vegetation and over water used higher frequencies, shorter call durations and shorter pulse intervals compared with species mostly hunting in open, uncluttered habitats. Peak frequency correlated negatively with body size. Regular frequency alternation between subsequent calls was typical in the search sequences of four out of 10 species. We discuss several hypotheses regarding the possible role of this frequency alternation, including species identification and partitioning of acoustic channels. Furthermore, we propose a model of how frequency alternation could increase the maximum detection distance of obstacles by marking search calls with different frequencies.

Habitat Variation and Jamming Avoidance in Echolocation Calls of the Sac-winged Bat (Balantiopteryx plicata)

We have studied the effect of habitat and presence of conspecifics on echolocation characteristics of the emballonurid bat Balantiopteryx plicata. Calls during the search phase only showed differences between habitats in bandwidth, as has been found for other open-space bats. Characteristics of calls during the approach phase did change when bats entered open areas. Calls in the terminal phase showed no differences in the characters examined between habitats. Bats flying in groups shifted their peak frequency significantly, which maximized differences between individuals. These results are interpreted as an active mechanism of jamming avoidance. Bats flying in groups also tended to increase the mean of peak frequencies.

Long-term training in a choice reaction time task reveals different learning characteristics for the visual and auditory system

Among the vertebrates, birds and bats are capable of active flight. For active fliers soaring is considered to be the most energy-saving way to meet their needs, as energy is extracted from natural winds and converted into a potential or kinetic form. For example, seabirds (gulls) soar to move between roosting and foraging areas, whereas others with high wing loadings (auks, cormorants) can only soar in strong winds [1]. Until now bats were considered to be unable to use soaring flight, due to their wing construction and lack of convective air currents during nighttime [1]. In Madurai, India, we were able to observe emballonurid bats (Taphozous sp.) soaring at altitudes between 50 and 250 m. For two consecutive nights on August 3 and 4, 1990 a group of at least 15 animals used the smooth slope of Keelakuyilkudi hill (130 m high) and strong winds for slope-soaring. Individual bats were observed soaring at constant position for at least 0.5 h, interrupted only by sudden changes in altitude which were controlled by wing strokes. These flight maneuvers included turns, yawing, and rolling. Due to the nature of these maneuvers we suggest that these flight activities indicate the pursuit of prey. After these brief interludes the bats resumed soaring and remained motionless in the air. Therefore, the bats may use soaring in their search for prey insects which fly at high altitudes. The observations were made with binoculars by the light of a full moon and hazy sky. The genus of the bats was identified by wing contours as Taphozous [2]. As only two species of Taphozous occur in the Madurai area, the soaring bats were either T. melanopogon, T. nudiventris, or both. The two species are known to feed at high altitudes [2]. The bats started soaring at about 7.30 p.m., i.e., 0.5 h after fly-out time. For soaring the bats exploit the strong winds over the top of Keelakuyilkudi hill which usually prevail in summer during daytime and only cease around midnight. Further research is underway to investigate the exact energetic conditions and food resources of insectivorous bats at this altitude, as both species are known for their opportunistic feeding behavior [2].

Vascularisation of the placenta in some bats

Vascularisation of the placenta of several species of bats representing 8 families is reported. Maternal vascularisation in all these bats is effected by a few large vessels which pass through the entire thickness of the placenta and give rise to numerous radial branches on reaching the foetal surface of the placenta. Maternal blood is returned through placental tubules which empty into large venous channels at the utero-placental junction. Foetal vascularisation is brought about by two allantoic arteries which capillarise over the placental tubules, and a large allantoic vein. In the exchange areas there is mostly crosscurrent circulation of the maternal and foetal bloods. Only in emballonurid bats is there an haematoma from which maternal blood is not drained back but is absorbed by cells of the trophoblast of chorionic villi.

Social Dispersion and Genetic Variation in Two Species of Emballonurid Bats

Abstract and SummarySaccopteryx leptura and S. bilineata are closely related, sympacric species of neotropical bats that exhibit marked differences in social organization and dispersion patterns. S. leptura is monogamous and roosts in small groups of 1 to 5 (Y = 2.6) individuals that are finely dispersed. S. bilineata is harem‐polygamous and roosts in larger groups of 1 to 42 (Y = 8.1) individuals that are more coarsely dispersed. Allozyme genetic studies of individuals from Trinidad, W I. demonstrate that both species carry similar, high levels of polymorphism and heterozygosity. Although significant genetic heterogeneity was observed among geographical populations of S. leptura, there is no evidence for either species that social structuring leads to inbreeding and the loss of heterozygosity, or that it promotes the development of genetic heterogeneity among social units that could accelerate the evolutionary diversification of these taxa. These results do not support a recently proposed hypothesis that social structuring in mammals has these effects.Observed intercolony genetic heterogeneity among adult males resident in multimale groups of S. bilineata is greater than intercolony heterogeneity of adult females. This is an apparent result of female dispersal and the recruitment of males into their parental groups. These results suggest that the adult males within large colonies may be kin‐related.

Social cues of a hipposiderid bat inside a cave fail to entrain the circadian rhythm of an emballonurid bat

Social cues of a hipposiderid bat inside a cave fail to entrain the circadian rhythm of an emballonurid bat

Echolocation calls of emballonurid bats from Panama

Saccopteryx bilineata, Cormura brevirostris and two other species tentatively identified as emballonurid bats, were recorded in the field in Panama. The search and approach phase calls of all the species began with a rise in frequency followed by a constant frequency (CF) portion and a terminal drop in frequency.S. bilineata and one of the unknown species produced pairs of calls, the first 2–3 kHz lower in CF frequency than the second. This has been suggested as associated with Doppler shifts of echoes caused by the bats' flight and bats' beaming calls towards different targets. However, a second unidentified species produced call triplets with the total difference in CF frequencies too great to be explained by this hypothesis. Increased bandwidth and integration of echo information, or social communication may be alternative functions. Terminal phase calls of three of the species were typical frequency modulated signals.C. brevirostris terminal calls, however, were CF in nature, a form not believed to be suitable for tasks requiring high resolution such as prey pursuit. The characteristics of these bats' signals are more complex than previously suggested and bring into question their supposed ‘primitive’ nature.

Un chiroptère emballonuridédans le Néogène d'Europe occidentale; Considérations paléobiogéographiques

The occurrence of an emballonurid bat is revealed within the micromammalian fauna found at the Lower Miocene locality of Port-la-Nouvelle (Aude). The material is described, and the comparison with homologous elements of fossil and living Emballonuridae indicates a modern character of the teeth.This species could be related to the recent genusTaphozous.. Therefore, a new family is added to the Western European mammalian Neogene fauna; and the Neogene geographical area of this family, previously limited to East Africa, is now extended to Europe.

Sunset-related timing of flight activity in neotropical bats.

The times of onset and completion of the hunting flights of three colonies of neotropical bats, each comprising 100-200 individuals, were observed for nine months. The colonies were of different species: Molossus ater (M.a.) and Molossus molossus (M.m.) of the Molossidae, and Myotis nigricans (My. n.) of the Vespertilionidae. Individuals of Phyllostomus hastatus (P.h., Phyllostomidae) were also observed. All the bats roosted in a building near Restrepo, Colombia (4°16'N, 73°34'W). Times of emergence in the evening and the return of the last animals in the morning were recorded on 2 to 3 successive days each month. For all bats, the emergence time changed in parallel with that of sunset, and the return paralleled sunrise (Fig. 1). Accordingly, the duration of the activity period is positively correlated with the duration of the night. No annual periodic changes in phase (re sunset/sunrise) of the onset and end of flight activity could be demonstrated, but there was a close relationship between the timing of activity and particular light intensities during twilight (Fig. 4). The first flyers of M.a. appear at the highest intensity (30-300 lx) and those of My. n. at the lowest (0.1-5 lx); the last flyers to return appear in the opposite sequence. For each species, the return to the roost usually occurs at a lower intensity than the departure. These findings, made with four neotropical bat species, differ from those of Subbaraj and Chandrashekaran (1977) with the emballonurid bat Taphozous that they studied at 9°58' N in India. The ecological factors that may play a role in timing the flight activity of tropical bats are discussed. "Sunset-related timing", based on the combined effect of (a) the circadian oscillation in "arousal" and (b) the transition during twilight to a light-intensity range with reduced inhibition of activity (lightsampling behavior), tends to be the rule in tropical bats; "time-of-day-related timing" is the exception.

Social organization and foraging in emballonurid bats

Social organization and foraging in emballonurid bats

Social organization and foraging in emballonurid bats

1. Graphical methods are presented for the simultaneous comparisons of group size and territory size (subsumed jointly under the term “social dispersion”), in organisms with exclusive but contiguous territories. The methods are applied to recently published data on five species of neotropical emballonurid bats with particular emphasis on identifying the factors which set maximal limits on group size. The available evidence suggests that population densities, group territory sizes, and group sizes are all limited by components of the food distribution. More particularly, it is argued that minimization of annual foraging ranges is of advantage to these bats and leads to a colony territory size containing one and only one active food site at any given time. Territory size is thus determined by the average distance between successively available food sites, the number of such sites needed per year, and the average size of these sites. Maximal group size is then determined as a result of this territory size minimization and equals average richness of currently used food patches. 2. The model predicts that where food patches are low in richness and close together, social dispersion will be fine-grained; where patches are high in richness and occur far apart, social dispersion will be coarse-grained. Since sites in this study which have many small patches tend to be located in the more stable habitats, the model also predicts that temporal stability in group size and unimodal frequency distributions of group size over space will be associated with fine-grained dispersions. The reverse is predicted for coarse-grained social dispersions. 3. The model only predicts the maximal size colonies can take. Among the many possible factors promoting social aggregation up to the predicted maxima, only a few account for the observed congruence in colony sizes and compositions at the roost and on the foraging grounds. These include information transfer about new food sites, location of roosts centrally to reduce energy costs of transit (Horn, 1968), and stabilization of competition with conspecifics at food sites.

Social organization and foraging in emballonurid bats

Social organization and foraging in emballonurid bats

Social organization and foraging in emballonurid bats

Social organization and foraging in emballonurid bats