Tiger moths and the threat of bats: decision-making based on the activity of a single sensory neuron

Echolocating bats and eared moths are a model system of predator–prey interaction within an almost exclusively auditory world. Through selective pressures from aerial-hawking bats, noctuoid moths have evolved simple ears that contain one to two auditory neurons and function to detect bat echolocation calls and initiate defensive flight behaviours. Among these moths, some chemically defended and mimetic tiger moths also produce ultrasonic clicks in response to bat echolocation calls; these defensive signals are effective warning signals and may interfere with bats'' ability to process echoic information. Here, we demonstrate that the activity of a single auditory neuron (the A1 cell) provides sufficient information for the toxic dogbane tiger moth, Cycnia tenera, to decide when to initiate defensive sound production in the face of bats. Thus, despite previous suggestions to the contrary, these moths'' only other auditory neuron, the less sensitive A2 cell, is not necessary for initiating sound production. However, we found a positive linear relationship between combined A1 and A2 activity and the number of clicks the dogbane tiger moth produces.     

The role of prey-generated sounds,vision, and echolocation in prey localization by the African batCardioderma cor (Megadermatidae)

Summary Cardioderma cor responded with head movements and flight toward speakers broadcasting calls of frogs and crickets which contained only sonic frequencies. Unlike the frog-eating bat,Trachops cirrhosus, they did not make contact with the speakers. Prey movements that generated sonic and ultrasonic sounds were both sufficient and necessary for the bats to localize and capture prey. Prey dragged across a glass sheet with a thin layer of water did not generate sounds and bats did not attempt to capture these prey, even with the availability of visual and echolocation cues. There was no evidence for the use of visual cues while hunting; bats did not localize prey more readily in light than darkness. Prey were presented such that their movements initially generated sounds, but then the prey moved onto the water layer of the glass sheet and sounds were eliminated. The bats emitted echolocation signals while hunting in this situation; however, the information from these signals was not utilized. The bats landed at the site that prey last made sound. These results demonstrate the importance of passive hearing for prey localization in this bat, and further suggest that when preygenerated sounds and echolocation signals offer conflicting information the bat's behavior is guided by the former.     

Convergent evolution of anti-bat sounds

Bats and their insect prey rely on acoustic sensing in predator prey encounters—echolocation in bats, tympanic hearing in moths. Some insects also emit sounds for bat defense. Here, we describe a previously unknown sound-producing organ in Geometrid moths—a prothoracic tymbal in the orange beggar moth (Eubaphe unicolor) that generates bursts of ultrasonic clicks in response to tactile stimulation and playback of a bat echolocation attack sequence. Using scanning electron microscopy and high-speed videography, we demonstrate that E. unicolor and phylogenetically distant tiger moths have evolved serially homologous thoracic tymbal organs with fundamentally similar functional morphology, a striking example of convergent evolution. We compared E. unicolor clicks to that of five sympatric tiger moths and found that 9 of 13 E. unicolor clicking parameters were within the range of sympatric tiger moths. Remaining differences may result from the small size of the E. unicolor tymbal. Four of the five sympatric clicking tiger moth species were unpalatable to bats (0–20 % eaten), whereas E. unicolor was palatable to bats (86 % eaten). Based on these results, we hypothesize that E. unicolor evolved tymbal organs that mimic the sounds produced by toxic tiger moths when attacked by echolocating bats.     

Echolocating bats cry out loud to detect their prey

Echolocating bats have successfully exploited a broad range of habitats and prey. Much research has demonstrated how time-frequency structure of echolocation calls of different species is adapted to acoustic constraints of habitats and foraging behaviors. However, the intensity of bat calls has been largely neglected although intensity is a key factor determining echolocation range and interactions with other bats and prey. Differences in detection range, in turn, are thought to constitute a mechanism promoting resource partitioning among bats, which might be particularly important for the species-rich bat assemblages in the tropics. Here we present data on emitted intensities for 11 species from 5 families of insectivorous bats from Panamá hunting in open or background cluttered space or over water. We recorded all bats in their natural habitat in the field using a multi-microphone array coupled with photographic methods to assess the bats' position in space to estimate emitted call intensities. All species emitted intense search signals. Output intensity was reduced when closing in on background by 4-7 dB per halving of distance. Source levels of open space and edge space foragers (Emballonuridae, Mormoopidae, Molossidae, and Vespertilionidae) ranged between 122-134 dB SPL. The two Noctilionidae species hunting over water emitted the loudest signals recorded so far for any bat with average source levels of ca. 137 dB SPL and maximum levels above 140 dB SPL. In spite of this ten-fold variation in emitted intensity, estimates indicated, surprisingly, that detection distances for prey varied far less; bats emitting the highest intensities also emitted the highest frequencies, which are severely attenuated in air. Thus, our results suggest that bats within a local assemblage compensate for frequency dependent attenuation by adjusting the emitted intensity to achieve comparable detection distances for prey across species. We conclude that for bats with similar hunting habits, prey detection range represents a unifying constraint on the emitted intensity largely independent of call shape, body size, and close phylogenetic relationships.     

Numerical and Functional Responses of Forest Bats to a Major Insect Pest in Pine Plantations

Global change is expected to modify the frequency and magnitude of defoliating insect outbreaks in forest ecosystems. Bats are increasingly acknowledged as effective biocontrol agents for pest insect populations. However, a better understanding is required of whether and how bat communities contribute to the resilience of forests to man- and climate-driven biotic disturbances. We studied the responses of forest insectivorous bats to a major pine defoliator, the pine processionary moth pityocampa, which is currently expanding its range in response to global warming. We used pheromone traps and ultrasound bat recorders to estimate the abundance and activity of moths and predatory bats along the edge of infested pine stands. We used synthetic pheromone to evaluate the effects of experimentally increased moth availability on bat foraging activity. We also evaluated the top-down regulation of moth population by estimating T. pityocampa larval colonies abundance on the same edges the following winter. We observed a close spatio-temporal matching between emergent moths and foraging bats, with bat activity significantly increasing with moth abundance. The foraging activity of some bat species was significantly higher near pheromone lures, i.e. in areas of expected increased prey availability. Furthermore moth reproductive success significantly decreased with increasing bat activity during the flight period of adult moths. These findings suggest that bats, at least in condition of low prey density, exhibit numerical and functional responses to a specific and abundant prey, which may ultimately result in an effective top-down regulation of the population of the prey. These observations are consistent with bats being useful agents for the biocontrol of insect pest populations in plantation forests.     

Moth wing scales slightly increase the absorbance of bat echolocation calls

Coevolutionary arms races between predators and prey can lead to a diverse range of foraging and defense strategies, such as countermeasures between nocturnal insects and echolocating bats. Here, we show how the fine structure of wing scales may help moths by slightly increasing sound absorbance at frequencies typically used in bat echolocation. Using four widespread species of moths and butterflies, we found that moth scales are composed of honeycomb-like hollows similar to sound-absorbing material, but these were absent from butterfly scales. Micro-reverberation chamber experiments revealed that moth wings were more absorbent at the frequencies emitted by many echolocating bats (40-60 kHz) than butterfly wings. Furthermore, moth wings lost absorbance at these frequencies when scales were removed, which suggests that some moths have evolved stealth tactics to reduce their conspicuousness to echolocating bats. Although the benefits to moths are relatively small in terms of reducing their target strengths, scales may nonetheless confer survival advantages by reducing the detection distances of moths by bats by 5-6%.     

Experimental evidence for group hunting via eavesdropping in echolocating bats

Group foraging has been suggested as an important factor for the evolution of sociality. However, visual cues are predominantly used to gain information about group members'' foraging success in diurnally foraging animals such as birds, where group foraging has been studied most intensively. By contrast, nocturnal animals, such as bats, would have to rely on other cues or signals to coordinate foraging. We investigated the role of echolocation calls as inadvertently produced cues for social foraging in the insectivorous bat Noctilio albiventris. Females of this species live in small groups, forage over water bodies for swarming insects and have an extremely short daily activity period. We predicted and confirmed that (i) free-ranging bats are attracted by playbacks of echolocation calls produced during prey capture, and that (ii) bats of the same social unit forage together to benefit from passive information transfer via the change in group members'' echolocation calls upon finding prey. Network analysis of high-resolution automated radio telemetry confirmed that group members flew within the predicted maximum hearing distance 94±6 per cent of the time. Thus, echolocation calls also serve as intraspecific communication cues. Sociality appears to allow for more effective group foraging strategies via eavesdropping on acoustical cues of group members in nocturnal mammals.     

Plasticity in echolocation calls of <Emphasis Type="Italic">Myotis macrodactylus</Emphasis> (Chiroptera: Vespertilionidae): implications for acoustic identification

Poor knowledge of the intraspecific variability in echolocation calls is recognized as an important limiting factor for the accurate acoustic identification of bats. We studied the echolocation behaviors of an ecologically poorly known bat species, Myotis macrodactylus, while they were commuting in three types of habitats differing significantly in the amount of background clutter, as well as searching for prey above the water surface in a river. Results showed that M. macrodactylus altered their echolocation call structure in the same way during commuting as foraging bats do in relation to the changing level of clutter. With increasing level of clutter, M. macrodactylus generally produced echolocation calls with higher start, end, and peak frequencies; wider bandwidth; and shorter pulse duration. Compared to commuting, bats emitted significantly lower frequency calls with narrower bandwidth while searching for prey. Discriminant function analysis indicated that 79.8% of the calls from the three commuting habitats were correctly grouped, and 87% of the calls were correctly classified to the commuting and foraging contexts. Our finding has implications for those who would identify species by their calls.     

Substrate-gleaning versus aerial-hawking: plasticity in the foraging and echolocation behaviour of the long-eared bat,Myotis evotis

The foraging and echolocation behaviour of Myotis evotis was investigated during substrate-gleaning and aerial-hawking attacks. Bats gleaned moths from both the ground and a bark-covered trellis, however, they were equally adept at capturing flying moths. The calls emitted by M. evotis during substrate-gleaning sequences were short, broadband, and frequency-modulated (FM). Three behavioural phases were identified: search, hover, and attack. Gleaning search calls were significantly longer in duration, lower in highest frequency, and larger in bandwidth than hover/attack calls. Calls were detected in only 68% of gleaning sequences, and when they were emitted, bats ceased calling 200 ms before attacking. Terminal feeding buzzes, the rapid increase in pulse repetition rate associated with an attempted prey capture, were never recorded during gleaning attacks. The echolocation calls uttered by M. evotis during aerial-hawking foraging sequences were also short duration, high frequency, FM calls. Two distinct acoustic phases were identified: approach and terminal. Approach calls were significantly different from terminal calls in all variables measured. Calls were detected in 100% of aerial-hawking attacks and terminal feeding buzzes were invariably produced. Gleaning hover/attack calls were spectrally similar to aerial approach calls, but were shorter in duration and emitted at a significantly lower (but constant) repetition rate than aerial signals. Although the foraging environment (flight cage contents) remained unchanged between tasks (substrate-gleaning vs. aerial-hawking), bats emitted significantly lower amplitude calls while gleaning. We conclude that M. evotis adjusts its echolocation behaviour to meet the perceptual demands (acoustical constraints) imposed by each foraging situations.Abbreviations BW bandwidth - CF constant frequency - dB SPL decibels sound pressure level - FM frequency modulated - HF highest frequency - LF lowest frequency - PF peak frequency Presented at the meeting Acoustic Images in Bat Sonar, a conference on FM echolocation honoring Donald R. Griffin's contributions to experimental biology (June 14–16, Brown University, Providence RI).     

Predator detection and evasion by flying insects

Echolocating bats detect prey using ultrasonic pulses, and many nocturnally flying insects effectively detect and evade these predators through sensitive ultrasonic hearing. Many eared insects can use the intensity of the predator-generated ultrasound and the stereotyped progression of bat echolocation pulse rate to assess risk level. Effective responses can vary from gentle turns away from the threat (low risk) to sudden random flight and dives (highest risk). Recent research with eared moths shows that males will balance immediate bat predation risk against reproductive opportunity as judged by the strength and quality of conspecific pheromones present. Ultrasound exposure may, in fact, bias such decisions for up to 24 hours through plasticity in the CNS olfactory system. However, brain processing of ultrasonic stimuli to yield adaptive prey behaviors remains largely unstudied, so possible mechanisms are not known.     

Echolocation calls of free-flying common vampire bats Desmodus rotundus (Chiroptera: Phyllostomidae) in Chile

We recorded and characterized the echolocation calls emitted by the common vampire bat Desmodus rotundus during foraging in natural habitats in Chile. Signal design typically shows multiple harmonics consisting of a brief quasi-constant frequency (QCF) component at the beginning of the pulse followed by a downward frequency modulated component. Calls are characterized by long durations (5.5 ms) and emitted as single pulses or in groups of 2–3 pulses at a repetition rate of 29 Hz. The higher frequency ranges (85–35 kHz) and the unusual QCF component that characterized multiharmonic signals of free-flying D. rotundus in Chile is a remarkable feature for acoustic identification with other Chilean bats.     

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

Studying 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.     

Airport noise disturbs foraging behavior of Japanese pipistrelle bats

The expansion of anthropogenic noise poses an emerging threat to the survival and reproductive success of various organisms. Previous investigations have focused on the detrimental effects of anthropogenic noise on the foraging behavior in some terrestrial and aquatic animals. Nevertheless, the role of airport noise in impairing foraging activities of most wild animals has been neglected. Here, we aimed to assess whether foraging behavior in free‐living Japanese pipistrelle bats (Pipistrellus abramus) can be disturbed by airport noise. We used audio recording to monitor foraging activities of bats at 11 sites around the runway of a municipal airport. We quantified noise level and spectra, aircraft activity, habitat type, nightly temperature, wind speed, and moon phase for each site. The analysis revealed that noise level and aircraft activity were significant negative predictors for the number of bat passes and feeding buzzes around the runway, even after controlling for the effects of other environmental factors. There was no marked spectral overlap between bat echolocation pulses and airport noise in the presence and absence of low‐flying aircraft. The spectro‐temporal parameters of echolocation vocalizations emitted by bats were dependent on noise level, aircraft activity, and habitat type. These results provide correlative evidence that airport noise can reduce foraging activities of wild pipistrelle bats. Our findings add to the current knowledge of adverse impacts of airport noise on foraging bats in artificial ecosystems and provide a basis for further research on the mechanisms behind noise pollution near airports.     

Three‐dimensional stratification pattern in an old‐growth lowland forest: How does height in canopy and season influence temperate bat activity?

The study of animal–habitat interactions is of primary importance for the formulation of conservation recommendations. Flying, gliding, and climbing animals have the ability to exploit their habitat in a three‐dimensional way, and the vertical canopy structure in forests plays an essential role for habitat suitability. Forest bats as flying mammals may seasonally shift their microhabitat use due to differing energy demands or changing prey availability, but the patterns are not well understood. We investigated three‐dimensional and seasonal habitat use by insectivorous bats in a temperate lowland old‐growth forest, the Belovezhskaya Pushcha in Belarus. We acoustically sampled broadleaved and mixed coniferous plots in the forest interior and in gaps in three heights during two reproductive periods (pregnancy/lactation vs. postlactation). In canopy gaps, vertical stratification in bat activity was less pronounced than in the forest interior. Vertical activity patterns differed among species. The upper canopy levels were important foraging habitats for the open‐space forager guild and for some edge‐space foragers like the Barbastelle bat Barbastella barbastellus and the soprano pipistrelle Pipistrellus pygmaeus. Myotis species had highest activity levels near the ground in forest gaps. Moreover, we found species‐dependent seasonal microhabitat shifts. Generally, all species and species groups considered except Myotis species showed higher activity levels during postlactation. Myotis species tended toward higher activity in the forest interior during postlactation. P. pygmaeus switched from high activity levels in the upper canopy during pregnancy and lactation to high activity levels near the ground during postlactation. We conclude that a full comprehension of forest bat habitat use is only possible when height in canopy and seasonal patterns are considered.     

Support for the allotonic frequency hypothesis in an insectivorous bat community

The allotonic frequency hypothesis proposes that certain insectivorous bat species can prey upon moths that can hear bat echolocation calls by using echolocation frequencies outside the sensitivity range of moth ears. The hypothesis predicts that the peak frequencies of bat echolocation calls are correlated with the incidence of moths in the diets of these bats. The aim of this study was to test this prediction on a bat community dominated by bats using low duty cycle echolocation calls, i.e. aerial foraging, insectivorous species using frequency modulated calls. The community consisted of nine species, two molossids, Sauromys petrophillus and Tadarida aegyptiaca, five vespertilionids, Eptesicus capensis, Eptesicus hottentotus, Miniopteris schreibersii, Myotis tricolor, and Myotis lesueuri, one rhinolophid, Rhinolophus clivosus, and one nycterid, Nycteris thebaica. The insect fauna in the habitat used by the bat community was suited to the testing of the allotonic frequency hypothesis because more than 90% of the moths comprising the insect fauna were tympanate. These included Pyralidae (3.8%), Geometridae (44.9%), Notodontidae (3.8%), Arctiidae (4.6%), Lymantriidae (0.8%) and Noctuidae (32.4%). As predicted, peak echolocation frequency was correlated with the incidence of moths in the diets of these nine species (r=0.98, df=7, P<0.01). Furthermore, multivariate analysis revealed that echolocation frequency (t=9.91, n=129, P<0.001) was a better predictor of diet than forearm length (t=5.51, n=129, P<0.001) or wing area (t=-3.41, n=129, P<0.001). This suggests that the selection pressure exerted by moth hearing might have acted directly on call frequency and secondarily on body size and wing morphology, as part of the same adaptive complex. It is unlikely that dietary differences were due to temporal and spatial differences in the availability of prey because the pattern of differences in skull morphology of the nine species supported our dietary analyses. The skull morphology of a bat represents a historical record of the kind of diet it has become adapted to over its evolutionary history. These results suggest that prey defences may mediate other factors structuring bat communities, e.g. competition. Competition may be reduced for those species of bats that can circumvent prey defences.     

Listening for bats: pulse repetition rate as a cue for a defensive behavior inCycnia tenera (Lepidoptera:Arctiidae)

Summary The tympanate, arctiid moth,Cycnia tenera responds to pulsed, 30 kHz acoustic stimuli resembling bat echolocation signals by emitting trains of clicks. This phonoresponse was used to determine that this moth is maximally sensitive to stimulus pulse repetition rates of 30–50 pulses/s, rates typically emitted by bats shortly before they close with their targets. At rates both above and below this optimum moths exhibit higher thresholds and reduced responsiveness. These data suggest thatC. tenera is capable of using the repetition rate emitted by an approaching bat as a cue in determining the relative proximity of the bat. The use of repetition rate information should allow this moth both an unambiguous indication of a bat at very close range as well as the ability to distinguish sources of nocturnal, high-frequency sounds not emitted by predators.     

Female greater wax moths reduce sexual display behavior in relation to the potential risk of predation by echolocating bats

Female greater wax moths Galleria mellonella display by wing fanning in response to bursts of ultrasonic calls produced bymales. The temporal and spectral characteristics of these callsshow some similarities with the echolocation calls of batsthat emit frequency-modulated (FM) signals. Female G. mellonellatherefore need to distinguish between the attractive signalsof male conspecifics, which may lead to mating opportunities,and similar sounds made by predatory bats. We therefore predictedthat (1) females would display in response to playbacks of male calls; (2) females would not display in response to playbacksof the calls of echolocating bats (we used the calls of Daubenton'sbat Myotis daubentonii as representative of a typical FM echolocatingbat); and (3) when presented with male calls and bat callsduring the same time block, females would display more whenperceived predation risk was lower. We manipulated predationrisk in two ways. First, we varied the intensity of bat callsto represent a nearby (high risk) or distant (low risk) bat.Second, we played back calls of bats searching for prey (lowrisk) and attacking prey (high risk). All predictions weresupported, suggesting that female G. mellonella are able todistinguish conspecific male mating calls from bat calls, andthat they modify display rate in relation to predation risk.The mechanism (s) by which the moths separate the calls ofbat and moth must involve temporal cues. Bat and moth signalsdiffer considerably in duration, and differences in durationcould be encoded by the moth's nervous system and used in discrimination.     

The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems

At first sight, echolocating bats face a difficult trade-off. As flying animals, they would benefit from a streamlined geometric shape to reduce aerodynamic drag and increase flight efficiency. However, as echolocating animals, their pinnae generate the acoustic cues necessary for navigation and foraging. Moreover, species emitting sound through their nostrils often feature elaborate noseleaves that help in focussing the emitted echolocation pulses. Both pinnae and noseleaves reduce the streamlined character of a bat’s morphology. It is generally assumed that by compromising the streamlined charactered of the geometry, the head morphology generates substantial drag, thereby reducing flight efficiency. In contrast, it has also been suggested that the pinnae of bats generate lift forces counteracting the detrimental effect of the increased drag. However, very little data exist on the aerodynamic properties of bat pinnae and noseleaves. In this work, the aerodynamic forces generated by the heads of seven species of bats, including noseleaved bats, are measured by testing detailed 3D models in a wind tunnel. Models of Myotis daubentonii, Macrophyllum macrophyllum, Micronycteris microtis, Eptesicus fuscus, Rhinolophus formosae, Rhinolophus rouxi and Phyllostomus discolor are tested. The results confirm that non-streamlined facial morphologies yield considerable drag forces but also generate substantial lift. The net effect is a slight increase in the lift-to-drag ratio. Therefore, there is no evidence of high aerodynamic costs associated with the morphology of bat heads.     

Visual acuity,sensitivity and binocularity in a gleaning insectivorous bat,Macrotus californicus (Chiroptera: Phyllostomidae)

Behavioural tests were used to examine the visual acuity and sensitivity of Macrotus californicus, a 12–14-g desert bat known to use vision in the location of terrestrial prey. Optomotor responses indicate single point visual acuity as fine as 3′38″ of arc. For comparison, the same tests were applied to two other species of bats. Antrozous pallidus, a desert gleaner which locates prey by the sounds they produce, exhibited acuity of 15′ of arc, and Eptesicus fuscus, an aerial foraging species that uses echolocation to find prey, 60′ of arc. Both M. californicus and A. pallidus retained their acuity at light levels as low as 2×10⁻⁴ mL (approximately 2×10⁻³ lux), comparable to ground luminance on a clear, moonless night. The eyes of M. californicus were more anteriorly directed, and had twice the binocular overlap of the other species examined. Comparison of our data with results from other studies indicate that M. californicus has vision superior to other insectivorous bats, and at least equivalent to larger-eyed frugivorous and nectarivorous bats examined in previous studies.     

Mosquito Consumption by Insectivorous Bats: Does Size Matter?

Insectivorous bats have often been touted as biological control for mosquito populations. However, mosquitoes generally represent only a small proportion of bat diet. Given the small size of mosquitoes, restrictions imposed on prey detectability by low frequency echolocation, and variable field metabolic rates (FMR), mosquitoes may not be available to or profitable for all bats. This study investigated whether consumption of mosquitoes was influenced by bat size, which is negatively correlated with echolocation frequency but positively correlated with bat FMR. To assess this, we investigated diets of five eastern Australian bat species (Vespadelus vulturnus Thomas, V. pumilus Gray, Miniopterus australis Tomes, Nyctophilus gouldi Tomes and Chalinolobus gouldii Gray) ranging in size from 4-14 g in coastal forest, using molecular analysis of fecal DNA. Abundances of potential mosquito and non-mosquito prey were concurrently measured to provide data on relative prey abundance. Aedes vigilax was locally the most abundant mosquito species, while Lepidoptera the most abundant insect order. A diverse range of prey was detected in bat feces, although members of Lepidoptera dominated, reflecting relative abundance at trap sites. Consumption of mosquitoes was restricted to V. vulturnus and V. pumilus, two smaller sized bats (4 and 4.5 g). Although mosquitoes were not commonly detected in feces of V. pumilus, they were present in feces of 55 % of V. vulturnus individuals. To meet nightly FMR requirements, Vespadelus spp. would need to consume ~600-660 mosquitoes on a mosquito-only diet, or ~160-180 similar sized moths on a moth-only diet. Lower relative profitability of mosquitoes may provide an explanation for the low level of mosquito consumption among these bats and the absence of mosquitoes in feces of larger bats. Smaller sized bats, especially V. vulturnus, are likely to be those most sensitive to reductions in mosquito abundance and should be monitored during mosquito control activities.