Sympatric Insectivorous Bat Research Articles

Food Habit, Spatial, and Dietary Niche Overlap of Three Sympatric Insectivorous Bats (Chiroptera) in the West Region of Cameroon

Food Habit, Spatial, and Dietary Niche Overlap of Three Sympatric Insectivorous Bats (Chiroptera) in the West Region of Cameroon

Craniodental traits predict feeding performance and dietary hardness in a community of Neotropical free‐tailed bats (Chiroptera: Molossidae)

Abstract Form–function studies have established a strong link between dental morphology and the mechanical properties of food items, with animals evolving tooth shapes theoretically ideal for their diets. However, information on how teeth perform under natural conditions is rare, which limits the understanding of how dental morphology influences dietary ecology and niche partitioning within animal communities. Free‐tailed bats (Chiroptera: Molossidae) are a diverse clade of aerial insectivorous mammals that exhibit an outstanding variation in size and craniodental traits, which have been directly related to ecological segregation among sympatric species. We investigate the mechanisms that allow functional dietary specialization and trophic segregation among sympatric free‐tailed bat species inhabiting a Neotropical forest. To do so, we coupled data on 3D dental topographic metrics, head and skull dimensions, field‐collected feeding performance and dietary hardness measurements. We found that evolved differences in molar topography and skull size vary in tandem with the mechanical demands of prey items naturally consumed by sympatric molossid species. This may be explained by feeding performance capabilities resulting from both molar shape and the overall size of the feeding apparatus, which seem to allow efficient processing of prey items with specific mechanical properties. For instance, smaller bats with higher molar topographic values (sharper, more complex molars) and more gracile heads mainly feed on softer insects, whereas bigger bats with lower molar topographic values (blunter, less complex molars) and more robust heads mostly feed on tougher insects. Species with a broader range of sizes, craniodental morphologies and insect hardness are also present in the community. These results illustrate how the morphology and size of feeding structures, and how they perform, may facilitate trophic segregation among sympatric insectivorous bats. Similar mechanisms may help structure other communities of insectivorous mammals, therefore the approaches presented here could be used to generate a better understanding of the ecomorphological traits and processes that underlie their diversity. Read the free Plain Language Summary for this article on the Journal blog.

Early erratic flight response of the lucerne moth to the quiet echolocation calls of distant bats.

Nocturnal insects have evolved ultrasound-sensitive hearing in response to predation pressures from echolocating insectivorous bats. Flying tympanate moths take various evasive actions when they detect bat cries, including turning away, performing a steering/zigzagging flight and ceasing flight. In general, infrequent ultrasonic pulses with low sound intensities that are emitted by distant bats evoke slight turns, whereas frequent and loud ultrasonic pulses of nearby bats evoke erratic or rapid unpredictable changes in the flight path of a moth. Flight cessation, which is a freezing response that causes the moth to passively dive (drop) to the ground, is considered the ultimate last-ditch evasive behaviour against approaching bats where there is a high predation threat. Here, we found that the crambid moth Nomophila nearctica never performed passive dives in response to frequent and loud ultrasonic pulses of >60 dB sound pressure level (SPL) that simulated the attacking echolocation call sequence of the predominant sympatric insectivorous bat Eptesicus fuscus, but rather turned away or flew erratically, regardless of the temporal structure of the stimulus. Consequently, N. nearctica is likely to survive predation by bats by taking early evasive action even when it detects the echolocation calls of sympatric bats hunting other insects at a distance. Since aerially hawking bats can track and catch erratically flying moths after targeting their prey, this early escape strategy may be common among night-flying tympanate insects.

Importance of multi‐dimensional analyses of resource partitioning in highly mobile species assemblages

AbstractResource partitioning is an essential mechanism enabling species coexistence. The resources that are used by an animal are linked to its morphology and ecology. Therefore, similar species should use similar resources. The ecological niche of an individual summarizes all used resources and is therefore composed of several dimensions. Many methods are established to study different dimensions of an animal's niche. The aim of this study was to demonstrate that a combination of suitable methods is needed to study spatial and dietary resource partitioning of sympatric species in detail. We hypothesized that, while each individual method might identify differences between species, the combined results of several methods will lead to a more complete picture of spatial and dietary resource partitioning. As model organisms we chose the sympatric insectivorous bat species Myotis bechsteinii, M. nattereri, and P. auritus. We examined horizontal habitat use by telemetry, vertical habitat use by measuring δ13C, trophic position by measuring δ15N in wing membrane, and diet composition by molecular fecal analysis. Our results show that each method is able to provide information about spatial/dietary resource partitioning. However, considering further dimensions by combining several methods allows a more comprehensive assessment of dietary and spatial resource partitioning in bats.

Seasonal reliance on nectar by an insectivorous bat revealed by stable isotopes

Many animals have seasonally plastic diets to take advantage of seasonally abundant plant resources, such as fruit or nectar. Switches from insectivorous diets that are protein rich to fruits or nectar that are carbohydrate rich present physiological challenges, but are routinely done by insectivorous songbirds during migration. In contrast, insectivorous bat species are not known to switch diets to consume fruit or nectar. Here, we use carbon stable isotope ratios to establish the first known case of a temperate bat species consuming substantial quantities of nectar during spring. We show that pallid bats (Antrozous pallidus) switch from a diet indistinguishable from that of sympatric insectivorous bat species in winter (when no cactus nectar is present) to a diet intermediate between those of insectivorous bats and nectarivorous bats during the spring bloom of a bat-adapted cactus species. Combined with previous results that established that pallid bats are effective pollinators of the cardon cactus (Pachycereus pringlei), our results suggest that the interaction between pallid bats and cardon cacti represents the first-known plant-pollinator mutualism between a plant and a temperate bat. Diet plasticity in pallid bats raises questions about the degree of physiological adaptations of insectivorous bats for incorporation of carbohydrate-rich foods, such as nectar or fruit, into the diet.

Who's for dinner? High‐throughput sequencing reveals bat dietary differentiation in a biodiversity hotspot where prey taxonomy is largely undescribed

Effective management and conservation of biodiversity requires understanding of predator-prey relationships to ensure the continued existence of both predator and prey populations. Gathering dietary data from predatory species, such as insectivorous bats, often presents logistical challenges, further exacerbated in biodiversity hot spots because prey items are highly speciose, yet their taxonomy is largely undescribed. We used high-throughput sequencing (HTS) and bioinformatic analyses to phylogenetically group DNA sequences into molecular operational taxonomic units (MOTUs) to examine predator-prey dynamics of three sympatric insectivorous bat species in the biodiversity hotspot of south-western Australia. We could only assign between 4% and 20% of MOTUs to known genera or species, depending on the method used, underscoring the importance of examining dietary diversity irrespective of taxonomic knowledge in areas lacking a comprehensive genetic reference database. MOTU analysis confirmed that resource partitioning occurred, with dietary divergence positively related to the ecomorphological divergence of the three bat species. We predicted that bat species' diets would converge during times of high energetic requirements, that is, the maternity season for females and the mating season for males. There was an interactive effect of season on female, but not male, bat species' diets, although small sample sizes may have limited our findings. Contrary to our predictions, females of two ecomorphologically similar species showed dietary convergence during the mating season rather than the maternity season. HTS-based approaches can help elucidate complex predator-prey relationships in highly speciose regions, which should facilitate the conservation of biodiversity in genetically uncharacterized areas, such as biodiversity hotspots.

Resource partitioning by insectivorous bats in Jamaica.

In this investigation, we use variation in wing morphology, echolocation behaviour, patterns of habitat use and molecular diet analysis to demonstrate that six species of sympatric insectivorous bats in Jamaica show significant differences that could explain resource partitioning among the species. High-intensity echolocating species that used shorter, broadband signals and had shorter, broader wings (Pteronotus macleayii, Pteronotus quadridens, Mormoops blainvillii) foraged most in edge habitats, but differed in timing of peak activity. P. macleayii and M. blainvillii differed in diet, but low sample size precluded diet analysis for P. quadridens. High-intensity echolocating species that used longer, more narrowband signals and had longer, narrower wings (Molossus molossus, Tadarida brasiliensis) foraged most in open areas and differed in diet from the other species. Two disparate species were most active in clutter (dense vegetation). Pteronotus parnellii used high-duty-cycle echolocation apparently specialized for detecting fluttering targets in clutter. Macrotus waterhousii used low-intensity, broadband echolocation calls and presumably uses prey-generated sounds when foraging. These two species also differed in diet. Our data show that differences in morphology and echolocation behaviour coincide with differences in habitat use and diet, resulting in minimal overlap in resource use among species.

Factors Influencing the Emergence Times of sympatric Insectivorous Bat Species

The onset of activity in animals restricted to being active for only part of the day is one of the most fundamental aspects of their biology because it marks the beginning of activities that they need to do to survive and reproduce. Initiation of activity is subject to several factors including presence/absence of predators and the vagaries of environmental conditions at the time of emergence. We tested if the emergence times amongst seven species of sympatric insectivorous bats were explained by predation risk, insect activity and weather conditions. We measured bat emergence times by recording echolocation calls. Peak emergence was correlated with body size, time of sunset, foraging strategy and diet, factors associated with risk of predation. Larger, faster flying bat species emerged earlier than smaller, slower flying species suggesting the former relied on flight speed to avoid predation. Clutter foragers emerged earlier than clutter-edge and open foragers, suggesting that vegetative cover is importa...

Identification of prey ofMyotis septentrionalisusing DNA-based techniques

Identifying and characterizing trophic linkages is fundamental to understanding how prey availability affects predator behavior, distribution, and density, and to elucidating the extent to which predators regulate prey populations. Vertebrate insectivores, such as bats, are a pervasive top-down force on insect populations in forest ecosystems. Bats are predators sensitive to habitat perturbations, whose prey selection behavior warrants further study. We identified trophic connections between a forest bat (Myotis septentrionalis) and its prey by isolating and sequencing cytochrome c oxidase subunit I gene (COI) fragments of insect prey obtained from bat fecal samples. Prey identities were inferred using GenBank and the Barcode of Life Data System (BOLD). We also identified prey remains morphologically from the same fecal samples, allowing comparisons across novel (GenBank and BOLD) and traditional (morphological) techniques. Lepidopterans were the most frequently detected prey in all approaches. Detection of common insect orders varied across procedures (P , 0.001), suggesting methodological bias at coarse taxonomic resolutions. Of the DNA-based approaches, GenBank provided the more diverse assessment of prey. We reveal trophic linkages for northern bats by identifying 20 prey genera and species using BOLD, more than one-half of which were smaller lepidopterans. The disproportionate number of smaller lepidopteran prey (mean [6SE] wingspan 24.2 6 2.05 mm) exceeded expectations based on field-based assessments. M. septentrionalis is known to use both aerial-hawking and gleaning behaviors. Lepidopteran prey consumed by M. septentrionalis were smaller than reported for conspecfic genera, suggesting this species differentiates itself from sympatric insectivorous bats with the prey it selects.

Diet of three sympatric insectivorous bat species on Ishigaki Island, Japan

We determined the food habits of 3 sympatric species of insectivorous bats (Rhinolophus perditus, Hipposideros turpis and Miniopterus fuscus) from May 2001 to January 2003 on Ishigaki Island, in the Ryukyu archipelago, Japan, by analysing their faecal samples. We also measured wing morphology of these 3 species and assessed insect abundance near the roost. Diet composition dif- fered between the 3 bat species throughout the survey period, except between R. perditus and M. fuscus from July to November 2002. R. perditus mainly consumed Coleoptera, Diptera, Lepidoptera and Hymenoptera, and the proportion of consumption of these insect orders changed seasonally. H. turpis mainly consumed Coleoptera from spring to summer. A large amount of Anomala albopilosa in particular seemed to be consumed. M. fuscus frequently consumed Diptera, Lepidoptera and Hymenoptera throughout the study period and Coleoptera in summer. Our results indicate resource partitioning between each species of bats; this partitioning may be caused by morphological differ- ences between the 3 species of bats, which may result in different passive prey selection. Because of the variation in diet composition, habitats that maintain high insect diversity are required for bat assemblage. In the future, the preferred foraging habitats of the 3 species of bats should be studied, and the results of these studies should be combined with our results for establishing an appropriate conservation measure.

Dietary composition and echolocation call design of three sympatric insectivorous bat species from China

AbstractStudying the diet of echolocating, insectivorous bats can provide important insights into their foraging behaviors and ecological constraints they are facing. By examining an extensive data set covering a period of 2 years, the present study identifies the dietary composition of three sympatric insectivorous bat species in rural areas of Beijing municipality. Each species clearly has different preferences for particular food items. Greater horseshoe bats, Rhinolophus ferrumequinum, preferred to catch nocturnal, actively flying insects, mostly moths (Lepidoptera), and to a lesser percentage flies (Diptera), beetles (Coleoptera), and flying ants and termites (Hymenoptera). Other nocturnal insects which do not exhibit any perceptible wing movements, such as true bugs (Homoptera), or strictly diurnal insects that hardly ever fly in the dark, such as grasshoppers (Orthoptera) and dragon‐ and damselflies (Odonata), were never found in droppings of horseshoe bats. Large mouse‐eared bats, Myotis chinensis, preferentially glean relatively large terrestrial prey of the order Coleoptera (mostly carabid beetles) and Orthoptera, whereas greater tube‐nosed bats, Murina leucogaster, consume predominantly smaller, diurnal Coleoptera (mostly soldier beetles, Cantharidae, and ladybugs, Coccinellidae). Our findings also indicate previously not described, significant spectro‐temporal differences in the echolocation signals of M. chinensis and M. leucogaster. The results suggest that in our study area the dramatic differences in the dietary composition of these three bat species are mainly based upon differences in their foraging behaviors, including differences in their echolocation signal structure. The dietary data provide important background information for conservational efforts, such as habitat protection.

Food habits of sympatric insectivorous bats in southern Kyushu, Japan.

Five species of bats, Myotis nattereri, M. macrodactylus, Miniopterus fuliginosus, Rhinolophus ferrumequinum and R. cornutus were found to forage in the same habitats in southern Kyushu, Japan. M. nattereri fed mainly on Lepidoptera, Coleoptera, Diptera and Araneae, the proportions of each of these in the diet fluctuating seasonally, however, Lepidoptera and Coleoptera, especially, were consumed selectively. Their available prey items ranged in body length from 5-13 mm in length. M. macrodactylus preyed mainly on Diptera, Trichoptera and Lepidoptera, that were larger (7-20 mm) than those eaten by M. nattereri. Small or medium-sized Lepidoptera constituted the bulk of M. fuliginosus' diet in summer. R. ferrumequinum fed chiefly on larger Diptera, Coleoptera and Lepidoptera measuring 8-45 mm in body length, and clearly selected beetles despite these being relatively few in the trap samples. Lepidoptera and Diptera measuring 7-23 mm were important dietary components for R. cornutus, and despite their abundance being relatively low in summer moths were selectively preyed upon. These five bat species selectively hunted particular prey species in addition to taking food opportunistically. Through differences in both foraging-site and in prey selection, they seem to be able to coexist in the same habitat.

Manoeuvrability and ecological segregation in the little brown (Myotis lucifugus) and Yuma (M. yumanensis) bats (Chiroptera: Vespertilionidae)

The abilities of two species of sympatric insectivorous bats, Myotis lucifugus and M. yumanensis, to negotiate a series of obstacle courses were measured. One hundred percent of the tested M. yumanensis were capable of negotiating their way through vertical strings 0.21 m apart, as compared with 30% of the tested M. lucifugus. A significant difference between the two species was found for this flight performance parameter, and this difference was found to be correlated with wing loading and wingspan. Myotis yumanensis has a lower wing loading and a lower wingspan than M. lucifugus, which probably explains the differences in manoeuvrability between the two species. An attempt was made to relate this difference to differences in the foraging behavior of the two species, but this was not possible, probably because of the high degree of morphological and behavioural overlap between the two species.