The relative influence of competition and prey defences on the trophic structure of animalivorous bat ensembles

Deterministic filters such as competition and prey defences should have a strong influence on the community structure of animals like animalivorous bats which have life histories characterized by low fecundity, low predation risk, long life expectancy and stable populations. We investigated the relative influence of these two deterministic filters on the trophic structure of animalivorous bat assemblages in South Africa. We used null models to test if patterns of dietary overlap were significantly different from patterns expected by chance and multivariate analyses to test the correlations between diet and phenotype (body size, wing morphology and echolocation). We found little evidence that competition structured the trophic niche of coexisting bats. Contrary to predictions from competition, dietary overlap between bats of ensembles and functional groups (open-air, clutter-edge, and clutter foragers) were significantly higher than expected by chance. Instead, we found support for the predictions of the allotonic frequency hypothesis: there were significant relationships between peak echolocation frequency and the proportion of moths in the diets of bats at local and regional scales, and peak echolocation frequency was the best predictor of diet even after we controlled for the influence of body size and phylogeny. These results suggest that echolocation frequency and prey hearing exert more influence on the trophic structure of sympatric animalivorous bats than competition. Nonetheless, differential habitat use and sensory bias may also be major determinants of trophic structure because these are also correlated with frequencies of bat calls.     

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.     

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.     

Flight performance, foraging tactics and echolocation in the trawling insectivorous bat Myotis adversus (Chiroptera: Vespertilionidae)

The bat Myotis adversus hunts for prey by aerial hawking and by taking prey from the water surface with its feet (trawling). The flight performance and echolocation of this species were studied in Queensland, Australia, and comparisons were made with Myotis daubentoni , a bat filling a similar ecological niche in the Palaearctic Region. The bats foraged in very similar ways, using the same foraging tactics and feeding in similar habitats, yet they were not geometrically similar in shape. The slightly larger Myotis adversus had relatively larger wings than M. daubentoni , conferring a slightly lower wing-loading. Nevertheless, M. adversus flew faster than M. daubentoni during the searching phase of foraging. Myotis daubentoni turned in tighter circles than M. adversus . Both species used short frequency-modulated (FM) echolocation calls of a characteristic sigmoidal structure, and nulls typically observed in the calls were an observational artefact. Myotis adversus also adopted an unusual 'long'FM call while foraging. The relations between echolocation frequencies and body size were explored in male M. adversus . Specialized morphological and acoustic adaptations for prey capture by trawling in insectivorous bats are discussed.     

食虫蝙蝠与昆虫之间的相互作用和协同进化关系

食虫蝙蝠与昆虫之间是捕食和被捕食的关系,夜行性昆虫是食虫蝙蝠主要的食物来源。在漫长的协同进化中,蝙蝠施加的捕食压力导致夜行性昆虫一系列特征的进化,其中一部分昆虫进化出能听到蝙蝠的超声波信号并采取逃跑行为或者能通过其它方式躲避蝙蝠,同时昆虫的适应性特征同样影响着蝙蝠的回声定位和捕食策略。本文从蝙蝠捕食昆虫的种类、昆虫对蝙蝠捕食的反应和食虫性蝙蝠对昆虫防卫的适应对策等三个方面对食虫蝙蝠与昆虫之间的相互关系进行了概述。     

The activity of an insectivorous bat Neoromicia nana on tracks in logged and unlogged forest in tropical Africa

Logging activities and the associated creation of roads and tracks can disturb and fragment forests, which may lead to a loss of forest‐dependent species and possibly favour nonforest generalists and edge species. The effects of such disturbance are poorly known for African insectivorous bats. We studied the activity patterns of insectivorous bats in a tropical African forest at Kibale National Park, Uganda, using an Anabat bat detector. The echolocation calls of the vespertilionid bat Neoromicia nana were the most frequently detected. This species was most active in the first 5 h after sunset with activity declining rapidly after midnight until sampling finished at 01:00 h. There was no difference in activity of N. nana levels between logged or undisturbed forest; however, this species exhibited higher levels of activity along the wide tracks running through the two forests than either 30 m off these tracks or along the narrow forest trails. The wing morphology and echolocation call of N. nana may be constraining it to flying in uncluttered space on the edge of the forest, penetrating mostly along wider tracks and roads. Further research (in particular radio‐telemetry) is required to test and validate these data.     

Female big brown bats, Eptesicus fuscus, recognize sex from a caller's echolocation signals

The echolocation calls of bats function in prey capture and navigation but are not commonly regarded as communicative signals. However, because bats' echolocation calls show patterns of variability, they may transmit information about a bat, such as its age, individual identity or sex. For echolocation calls to function in this manner, variation in calls must be reliably linked to the characteristics of the bat, as has been shown in a number of studies. However, few studies have asked whether bats respond to this variation. We tested whether female big brown bats can identify the sex of an unfamiliar bat from playbacks of its echolocation calls. Playback consisted of a 30-s preplayback period, a 60-s playback period of either male or female echolocation calls, and a 30-s postplayback period. In the playback and postplayback periods the vocalization rates of female bats changed significantly relative to the preplayback period depending on the sex of the playback stimulus, indicating that they could determine sex from the echolocation calls. These findings support the possibility that echolocation calls play a role in communication in big brown bats.     

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%.     

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.     

Ensemble composition and activity levels of insectivorous bats in response to management intensification in coffee agroforestry systems

Shade coffee plantations have received attention for their role in biodiversity conservation. Bats are among the most diverse mammalian taxa in these systems; however, previous studies of bats in coffee plantations have focused on the largely herbivorous leaf-nosed bats (Phyllostomidae). In contrast, we have virtually no information on how ensembles of aerial insectivorous bats--nearly half the Neotropical bat species--change in response to habitat modification. To evaluate the effects of agroecosystem management on insectivorous bats, we studied their diversity and activity in southern Chiapas, Mexico, a landscape dominated by coffee agroforestry. We used acoustic monitoring and live captures to characterize the insectivorous bat ensemble in forest fragments and coffee plantations differing in the structural and taxonomic complexity of shade trees. We captured bats of 12 non-phyllostomid species; acoustic monitoring revealed the presence of at least 12 more species of aerial insectivores. Richness of forest bats was the same across all land-use types; in contrast, species richness of open-space bats increased in low shade, intensively managed coffee plantations. Conversely, only forest bats demonstrated significant differences in ensemble structure (as measured by similarity indices) across land-use types. Both overall activity and feeding activity of forest bats declined significantly with increasing management intensity, while the overall activity, but not feeding activity, of open-space bats increased. We conclude that diverse shade coffee plantations in our study area serve as valuable foraging and commuting habitat for aerial insectivorous bats, and several species also commute through or forage in low shade coffee monocultures.     

Flight performance, echolocation and foraging behaviour in noctule bats Nyctalus noctula

The noctule Nyctulus noctula (Schreber, 1774) is a relatively large (c. 25 g) insectivorous bat which catches insects on the wing (by aerial hawking). Emergence at a maternity roost was earliest relative to sunset when females were lactating, and bats may then have risked predation by flying at higher light levels during a period of high energy demand. Flight performance was quantified by using stereophotogrammetry. At feeding sites bats flew at 6.0 ± 2.1 m/s. This was faster than predicted minimum power speed (V _mp), and either between V _mp and maximum range speed (V _mr), or close to their predicted V _mr, depending on which aerodynamic model of flight power requirements was used. The echolocation behaviour of noctules is flexible. Long duration, low frequency calls (c. 20 kHz) with little frequency modulation were emitted while cruising, but at foraging sites the calls became more frequency-modulated. As the noctule is traditionally thought of as using low frequency echolocation, it was expected to receive weak echoes from small targets and therefore to specialize in eating large insect prey. Although the bats ate mainly beetles, large numbers of small dipterans were also eaten. The noctule is probably able to detect such small items because, when foraging, its calls become broadband and sweep from high frequencies. Higher harmonics are also present, and these may assist in the detection of small prey. In noctules, as in many bats, there appears to be a 1:1 link between wingbeat and call production during the search phase of foraging.     

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.     

Patterns of island occupancy in bats: influences of area and isolation on insular incidence of volant mammals

Aim  The influence of landscape structure on the distribution patterns of bats remains poorly understood for many species. This study investigates the relationship between area and isolation of islands and the probability of occurrence of six bat species to determine whether persistence and immigration abilities vary among bat species and foraging guilds.
Location  Thirty-two islands in the Gulf of California near the Baja California peninsula in north-west Mexico.
Methods  Using logistic regression and Akaike information criterion (AIC) model selection, we compared five a priori models for each of six bat species to explain patterns of island occupancy, including random patterns, minimum area effects, maximum isolation effects, additive area and isolation effects and compensatory area and isolation effects.
Results  Five species of insectivorous bats ( Pipistrellus hesperus , Myotis californicus , Macrotus californicus , Antrozous pallidus and Mormoops megalophylla ) displayed minimum area thresholds on incidence. The probability of occurrence tended to decrease at moderate distances of isolation ( c . 10–15 km) for these species (excepting A. pallidus ). The distributions of two non-insectivorous species ( Leptonycteris curasoae and Myotis vivesi ) were not influenced by island size and isolation.
Main conclusions  Minimum area thresholds on incidence suggest that island occupancy by insectivorous bats may be limited by resource requirements. Islands smaller than 100 ha typically did not support occupancy or use by insectivorous bats, except at minimal isolation distances. Insectivorous bat species may also be more sensitive to moderate levels of habitat isolation in some landscape contexts than previously expected. Our results suggest that differences in foraging habits may have important implications for understanding the distribution patterns of bats.     

Does interspecific competition drive patterns of habitat use in desert bat communities?

Bodies of water are a key foraging habitat for insectivorous bats. Since water is a scarce and limiting resource in arid environments, bodies of open water may have a structuring effect on desert bat communities, resulting in temporal or spatial partitioning of bat activity. Using acoustic monitoring, we studied the spatial and temporal activity patterns of insectivorous bats over desert ponds, and hypothesised that sympatric bat species partition the foraging space above ponds based on interspecific competitive interactions. We used indirect measures of competition (niche overlap and competition coefficients from the regression method) and tested for differences in pond habitat selection and peak activity time over ponds. We examined the effect of changes in the activity of bat species on their potential competitors. We found that interspecific competition affects bat community structure and activity patterns. Competing species partitioned their use of ponds spatially, whereby each species was associated with different pond size and hydroperiod (the number of months a pond holds water) categories, as well as temporally, whereby their activity peaked at different hours of the night. The drying out of temporary ponds increased temporal partitioning over permanent ponds. Differences in the activity of species over ponds in response to the presence or absence of their competitors lend further support to the role of interspecific competition in structuring desert bat communities. We suggest that habitat use and night activity pattern of insectivorous bats in arid environments reflect the trade-offs between selection of preferred pond type or activity time and constraints posed by competitive interactions.     

‘No cost of echolocation for flying bats’ revisited

Echolocation is energetically costly for resting bats, but previous experiments suggested echolocation to come at no costs for flying bats. Yet, previous studies did not investigate the relationship between echolocation, flight speed, aerial manoeuvres and metabolism. We re-evaluated the 'no-cost' hypothesis, by quantifying the echolocation pulse rate, the number of aerial manoeuvres (landings and U-turns), and the costs of transport in the 5-g insectivorous bat Rhogeessa io (Vespertilionidae). On average, bats (n = 15) travelled at 1.76 ± 0.36 m s?1 and performed 11.2 ± 6.1 U-turns and 2.8 ± 2.9 ground landings when flying in an octagonal flight cage. Bats made more U-turns with decreasing wing loading (body weight divided by wing area). At flight, bats emitted 19.7 ± 2.7 echolocation pulses s?1 (range 15.3-25.8 pulses s?1), and metabolic rate averaged 2.84 ± 0.95 ml CO? min?1, which was more than 16 times higher than at rest. Bats did not echolocate while not engaged in flight. Costs of transport were not related to the rate of echolocation pulse emission or the number of U-turns, but increased with increasing number of landings; probably as a consequence of slower travel speed when staying briefly on ground. Metabolic power of flight was lower than predicted for R. io under the assumption that energetic costs of echolocation call production is additive to the aerodynamic costs of flight. Results of our experiment are consistent with the notion that echolocation does not add large energetic costs to the aerodynamic power requirements of flight in bats.     

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.     

Activity levels of bats and katydids in relation to the lunar cycle

Animals are exposed to many conflicting ecological pressures, and the effect of one may often obscure that of another. A likely example of this is the so-called “lunar phobia” or reduced activity of bats during full moon. The main reason for lunar phobia was thought to be that bats adjust their activity to avoid predators. However, bats can be prey, but many are carnivorous and therefore predators themselves. Thus, they are likely to be influenced by prey availability as well as predation risk. We investigated the activity patterns of the perch-hunting Lophostoma silvicolum and one of its main types of prey, katydids, to assess the influence of the former during different phases of the lunar cycle on a gleaning insectivorous bat. To avoid sampling bias, we used sound recordings and two different capture methods for the katydids, as well as video monitoring and radio-telemetry for the bats. Both, bats and katydids were significantly more active during the dark periods associated with new moon compared to bright periods around the full moon. We conclude that foraging activity of L. silvicolum is probably influenced by prey availability to a large extent and argue that generally the causes of lunar phobia are species-specific.     

Activity patterns of insectivorous bats and birds in northern Scandinavia (69° N), during continuous midsummer daylight

Previous studies suggest that many species of insectivorous bats are nocturnal, despite the relatively low availability of their insect prey at night, because of the risk of predation by diurnal predatory birds. We hypothesised that if this was the case bats living above the arctic circle would alter their feeding behaviour during midsummer because there would no longer be any benefit to restricting their activity to the period when their prey are least abundant. Alternatively, if bats were more influenced by competition from aerial insectivorous birds they would continue to feed at 'night' to avoid such competition. In northern Norway (69°  N), during continuous midsummer daylight, insectivorous sand martins ( Riparia riparia ) concentrated their aerial feeding activity when aerial insects were most abundant. The birds stopped feeding between 23:00 and 07:00 when aerial insects were least abundant. In contrast, northern bats ( Eptesicus nilssonii ), fed mostly between 22:00 and 02:00, coinciding with the lowest aerial insect availability, and with the period when light levels were lowest (ca 1000 lux). Bat activity patterns were closest to those predicted by the avian competition hypothesis. The low densities of both sand martins and Northern bats in the study area, however, were less consistent with this hypothesis. Possibly populations of both species were higher historically and the observed patterns reflected historical competition. Bat activity was most closely correlated to ambient light levels. This raised two alternative explanations that we could not eliminate. Perhaps there was differential predation risk, between the brightest and darkest parts of the day, because the visual capacities of falcons are strongly dependent on luminance. Alternatively the bats may have been entrained to emerge at given light levels by their behaviour at other times of year.     

Driving Factors for the Evolution of Species-Specific Echolocation Call Design in New World Free-Tailed Bats (Molossidae)

Phylogeny, ecology, and sensorial constraints are thought to be the most important factors influencing echolocation call design in bats. The Molossidae is a diverse bat family with a majority of species restricted to tropical and subtropical regions. Most molossids are specialized to forage for insects in open space, and thus share similar navigational challenges. We use an unprecedented dataset on the echolocation calls of 8 genera and 18 species of New World molossids to explore how habitat, phylogenetic relatedness, body mass, and prey perception contribute to echolocation call design. Our results confirm that, with the exception of the genus Molossops, echolocation calls of these bats show a typical design for open space foraging. Two lines of evidence point to echolocation call structure of molossids reflecting phylogenetic relatedness. First, such structure is significantly more similar within than among genera. Second, except for allometric scaling, such structure is nearly the same in congeneric species. Despite contrasting body masses, 12 of 18 species call within a relatively narrow frequency range of 20 to 35 kHz, a finding that we explain by using a modeling approach whose results suggest this frequency range to be an adaptation optimizing prey perception in open space. To conclude, we argue that the high variability in echolocation call design of molossids is an advanced evolutionary trait allowing the flexible adjustment of echolocation systems to various sensorial challenges, while conserving sender identity for social communication. Unraveling evolutionary drivers for echolocation call design in bats has so far been hampered by the lack of adequate model organisms sharing a phylogenetic origin and facing similar sensorial challenges. We thus believe that knowledge of the echolocation call diversity of New World molossid bats may prove to be landmark to understand the evolution and functionality of species-specific signal design in bats.     

Implications of sensory ecology for species coexistence: biased perception links predator diversity to prey size distribution

Inherent to sensory systems is a discrepancy between the perceived and the actual environment. We modelled prey perception in different species of echolocating bats and show that differences in sensory systems can be important for shaping the niches of animals and for structuring animal communities. We argue that sensory specialization can lower interspecific competition by making the same world appear different. We specifically raise the claim that it is important to consider the interaction of sensory bias and the distribution of (prey) resource size. Using a modeling approach we assessed the potential contribution of sensory bias for species coexistence for the example of bat echolocation. We show that even relatively small sensory differences among coexisting species can translate into significant differences in access to food resources, if prey size distribution is skewed towards small prey. Specifically, for the prey size distribution occurring most frequently in nature, differences in sensory access to resources seem large enough to relax competition and facilitate species coexistence. Interaction between sensory bias and prey size distribution in a way that enhances species coexistence may be a general phenomenon not limited to bat echolocation.