Trachops Research Articles

Predation of Natalus macrourus (Chiroptera: Natalidae) by Trachops cirrhosus (Chiroptera: Phyllostomidae) in a ferriferous Brazilian Amazon cave

Abstract Trachops cirrhosus bats are especially notable for feeding on various types of preys throughout its range, including other bat species. Here we report predation events of T. cirrhosus on Natalus macrourus, a new bat species among a wide range of prey.

A Species Complex in the Iconic Frog-Eating Bat Trachops cirrhosus (Chiroptera, Phyllostomidae) with High Variation in the Heart of the Neotropics

A Species Complex in the Iconic Frog-Eating Bat Trachops cirrhosus (Chiroptera, Phyllostomidae) with High Variation in the Heart of the Neotropics

Ripple effects in a communication network: anti-eavesdropper defence elicits elaborated sexual signals in rival males.

Emitting conspicuous signals into the environment to attract mates comes with the increased risk of interception by eavesdropping enemies. As a defence, a commonly described strategy is for signallers to group together in leks, diluting each individual's risk. Lekking systems are often highly social settings in which competing males dynamically alter their signalling behaviour to attract mates. Thus, signalling at the lek requires navigating fluctuations in risk, competition and reproductive opportunities. Here, we investigate how behavioural defence strategies directed at an eavesdropping enemy have cascading effects across the communication network. We investigated these behaviours in the túngara frog (Engystomops pustulosus), examining how a calling male's swatting defence directed at frog-biting midges indirectly affects the calling behaviour of his rival. We found that the rival responds to swat-induced water ripples by increasing his call rate and complexity. Then, performing phonotaxis experiments, we found that eavesdropping fringe-lipped bats (Trachops cirrhosus) do not exhibit a preference for a swatting male compared to his rival, but females strongly prefer the rival male. Defences to minimize attacks from eavesdroppers thus shift the mate competition landscape in favour of rival males. By modulating the attractiveness of signalling prey to female receivers, we posit that eavesdropping micropredators likely have an unappreciated impact on the ecology and evolution of sexual communication systems.

New reports of morphological anomalies in leaf-nosed bats (Chiroptera: Phyllostomidae) from Colombia

Abstract Morphological anomalies in bats are rarely reported. We present new reports of three types of morphological anomalies (chromatic, wing, and ear) from specimens in a biological collection and from individuals captured during field sampling. We recorded piebaldism on seven individuals from six species: Carollia perspicillata, Glossophaga commissarisi, Hsunycteris thomasi, Phyllostomus elongatus, and Trachops cirrhosus from Guaviare collected in 2022, and Tonatia saurophila from Casanare collected in 2020. These represent three new reports for the continent (P. elongatus, G. commissarisi, and H. thomasi). We also recorded the broken digits anomaly on two individuals from two species: Platyrrhinus sp. and Sturnira sp. from Chocó collected in 2019. In addition, we found one case of the absence of pinnae and tragus in C. perspicillata from Santander collected in 2018; an absence not previously reported in bats. We encourage researchers to report their observations of bats with morphological anomalies, as this information could be useful in estimating occurrence rates and addressing questions about its effects on populations.

Mid-flight prey switching in the fringed-lipped bat (Trachops cirrhosus).

While foraging, eavesdropping predators home in on the signals of their prey. Many prey signal from aggregations, however, and predators already en route to attack one individual often encounter the signals of other prey. Few studies have examined whether eavesdropping predators update their foraging decisions by switching to target these more recently signaling prey. Switching could result in reduced localization errors and more current estimates of prey location. Conversely, assessing new cues while already in pursuit of another target might confuse or distract a predator. We tested whether fringed-lipped bats (Trachops cirrhosus) switch prey targets when presented with new cues mid-approach and examined how switching and the distance between simulated prey influence attack accuracy, latency, and prey capture success. During nearly 80% of attack flights, bats switched between túngara frog (Engystomops pustulosus) calls spaced 1m apart, and switching resulted in lower localization errors. The switching rate was reduced, and the localization advantage disappeared for calls separated by 3m. Regardless of whether bats switched targets, attacks were less accurate, took longer, and were less often successful when calls were spaced at larger distances, indicating a distraction effect. These results reveal that fringed-lipped bats attend to cues from non-targeted prey during attack flights and that the distance between prey alters the effectiveness of attacks, regardless of whether a bat switches targets. Understanding how eavesdropping predators integrate new signals from neighboring prey into their foraging decisions will lead to a fuller picture of the ways unintended receivers shape the evolution of signaling behavior.

Long-term memory in frog-eating bats

Long-term memory has clear advantages for animals but also has neurological and behavioral costs1-3. Encoding memories is metabolically expensive1. Older memories can interfere with retrieval of more recent memories3, prolong decision-making and reduce cognitive flexibility2,3. Given these opposing selection pressures, understanding how long memories last can shed light on how memory enhances or constrains animals' abilities to exploit their niches. Although testing memory retention in wild animals is difficult, it is important because captive conditions do not reflect the complex cognitive demands of wild environments, and long-term captivity changes the brain4 (Data S1A). Here, we trained wild-caught frog-eating bats (Trachops cirrhosus) to find prey by flying to a novel acoustic cue. After they learned the rewarded sound, we released them back into the wild, and then re-captured some of them one to four years later. When re-tested, all eight 'experienced' bats that previously learned the novel prey sounds flew to those sounds within seconds, whereas 17 naïve bats tested with the same sounds showed weak responses. Experienced bats also showed behavior indicating generalization of memories between novel sounds and rewards over time. The frog-eating bat's remarkably long memory indicates that an ability to remember rarely encountered prey may be advantageous for this predator and suggests hitherto unknown cognitive abilities in bats.

Place your bets: small prey faces large predators

Abstract Interspecific aggression is common between species that live together. We describe such behaviour in a mixed-species bat roost. A single small-bodied (approx. 15 g) frugivorous bat, Carollia perspicillata, aggressively antagonized a group of much larger (approx. 34 g) bats, Trachops cirrhosus, in defence of a roosting site, resulting in the larger T. cirrhosus relinquishing the site. This interaction was striking as T. cirrhosus are known to consume C. perspicillata. The small ‘prey’ individual caused the group of larger ‘predators’ to leave the roosting area by intensely vocalizing, rapidly flapping its wings, hitting the faces of the other bats with its wings, and flinging its body at the other bats. To our knowledge, this type of interspecies agonistic behaviour has never been observed before in bats and highlights the importance of intensively studying behavioural interactions in nature.

Reproductive phenologies of phyllostomid bats in the Central Amazon

Mammals tend to align their most energetically demanding phenological events with periods of peak resource availability. Their reproductive phenology is influenced by local resource availability, potentially leading to geographical variation in their breeding strategy. Although the Amazon is the world’s epicenter of bat diversity, the reproductive phenology of Amazonian bats remains poorly known. Seasonality induces fluctuations in resource availability and most phyllostomid species, crucial agents of seed dispersal, pollination and arthropod suppression in the Neotropics, have been described to exhibit seasonal bimodal polyestry. However, current understanding of phyllostomid reproductive phenology is impaired by the paucity of comparative examinations of the phenologies of sympatric species, using consistent classification schemes based on the number and timing of annual peaks in pregnancy and lactation. Using a multi-year dataset from Central Amazonia, we examined the reproductive phenology of nine bat species (Artibeus concolor, A. obscurus, A. lituratus, Carollia brevicauda, C. perspicillata, Gardnerycteris crenulatum, Lophostoma silvicolum, Rhinophylla pumilio, and Trachops cirrhosus), as well as two feeding ensembles (i.e., frugivores and gleaning animalivores). Only three of the nine species exhibited a bimodal reproductive phenology. Six species and the frugivore ensemble showed unimodal reproductive phenology, while gleaning animalivores displayed an amodal pregnancy pattern. All species except L. silvicolum had their primary pregnancy peak during the mid-dry season. A reproductive peak during the early wet season, or local variation in the duration of the fruiting season may explain the deviation of our observations from the expected bimodal polyestry.

Plaguicidas organoclorados en murciélagos (Chiroptera) asociados al bosque húmedo tropical en Córdoba, Colombia

Investigaciones sobre toxicidad ambiental por pesticidas se han realizado principalmente en mamíferos terrestres, pero existe poca información sobre plaguicidas organoclorados en murciélagos. Teniendo en cuenta el papel funcional de este grupo en varios procesos ecosistémicos como insectívoros, frugívoros y polinizadores, su afectación puede estar causando un impacto negativo en la salud de los ecosistemas naturales. En Colombia, no hay estudios que documenten esta problemática; por tanto, el objetivo fue determinar la presencia de plaguicidas organoclorados en el ensamblaje de murciélagos del bosque húmedo tropical (bh-T) en Córdoba, Colombia. Se evaluó la presencia de organoclorados en hígado y músculo de murciélagos del sector Manso-Tigre, un área protegida con ocupación campesina. La concentración de plaguicidas organoclorados como Aldrin, Dieldrin, Endrin, Heptacloro epóxido, α-BCH, βBCH, γ-BCH, 2,4-DDD, 2,4-DDT, 4,4-DDE y 4,4-DDT, se determinó por cromatografía de gases. Niveles de organoclorados en hígado y músculo presentaron diferencias significativas (P<0,05). Se detectó mayor contenido de organoclorados en hígado en las especies Trachops cirrhosus (α–BCH, γ-BCH, Endrin, pp-DDE), Desmodus rotundus (β-BCH), Micronycteris microtis (Aldrin), Platyrrhinus helleri (Heptacloro) y Phyllostomus hastatus (pp-DDT). En tejido muscular, la concentración de organoclorados fue mayor en Trachops cirrhosus (α-BCH, γ-BCH, Endrin, pp-DDE), Artibeus planirostris (β-BCH), Micronycteris microtis (Aldrin, Heptacloro) y Phyllostomus hastatus (pp-DDT). La contaminación por organoclorados en murciélagos posiblemente está relacionada con el uso de agroquímicos, insecticidas y compuestos fosfatados para uso agrícola. Los resultados permiten reconocer a los murciélagos como bioindicadores de contaminación ambiental al indicar procesos de cambios o disturbios en los hábitats.

Context-dependent preferences in wild fruit bats

In models of choice, animals are expected to evaluate options in absolute terms and assign some fitness-related value to different options. These expectations are similar to those of economic rationality, and both predict consistent decisions across variable contexts. Evidence from humans and other animals suggests that decision-making mechanisms can lead to context-dependent choices, which are considered economically irrational. While there is widespread evidence that these mechanisms may influence animal decision making, we can now explore how the presence and degree of these biases may arise in different animals based on their taxonomy and ecology. Here, we investigated context-dependent decisions in wild Jamaican fruit bats, Artibeus jamaicensis . We found that bats were sensitive to the context of the choice, showing shifts in preference upon the addition of an irrelevant decoy option. These results contrast previous findings in a close relative, the frog-eating bat, Trachops cirrhosus , indicating that diet may play a critical role in these behaviours. We argue that comparative studies exploring the role of diet on these decision-making biases are critical for understanding how animals make foraging decisions in the wild. • Animals are generally expected to select the best option in a choice set. • We tested whether fruit bats show context-dependent foraging preferences. • The presence of an inferior choice influenced foraging preferences in fruit bats. • Comparative evaluation may be influenced by an animal's diet.

We eat meat: a review of carnivory in bats

Abstract Some bat species in the families Phyllostomidae, Megadermatidae, and Nycteridae have long been known to consume terrestrial vertebrates and, more recently, reports of aerial‐hawking vespertilionid carnivores have surfaced. We review the diets, hunting behaviour and roosting ecology of 17 bat species that are known to consume terrestrial vertebrates: Vampyrum spectrum, Chrotopterus auritus, Trachops cirrhosus, Macroderma gigas, Megaderma (Lyroderma) lyra, Nycteris grandis, Nyctalus lasiopterus, Nyctalus aviator, Ia io, Antrozous pallidus, Cardioderma cor, Phyllostomus hastatus, Mimon (Gardnerycteris) crenulatum, Mimon cozumelae, Tonatia saurophila, Tonatia bidens, and Lophostoma silvicolum. Data on their diet and roosts were obtained from 241 original works, with considerable differences in the amount of research and information available among species. Carnivorous bats were found to belong to an ecologically diverse group and share little but their diet. Therefore, we define a carnivorous bat as a bat that, either year‐round or seasonally, uses terrestrial vertebrates as the main component of its diet, at least in part of its geographic range. We conclude from available data that Mimon crenulatum, Lophostoma silvicolum, Mimon cozumelae, Phyllostomus hastatus, Tonatia bidens, Tonatia saurophila, Cardioderma cor, and Antrozous pallidus use vertebrates as a minor part of their diet and should not be considered carnivorous. The nine other species we reviewed do fit into the definition of carnivorous bats, and can be further subdivided based on their ecology and the seasonality of their habits into three categories: year‐round predominantly gleaning carnivores (Chrotopterus auritus, Trachops cirrhosus, and Vampyrum spectrum), seasonal predominantly gleaning carnivores (Megaderma lyra, Macroderma gigas, and Nycteris grandis) and seasonal aerial‐hawking bird‐eating carnivores (Ia io, Nyctalus aviator, and Nyctalus lasiopterus).

Covariation among multimodal components in the courtship display of the túngara frog.

Communication systems often include a variety of components, including those that span modalities, which may facilitate detection and decision-making. For example, female túngara frogs and fringe-lipped bats generally rely on acoustic mating signals to find male túngara frogs in a mating or foraging context, respectively. However, two additional cues (vocal sac inflation and water ripples) can enhance detection and choice behavior. To date, we do not know the natural variation and covariation of these three components. To address this, we made detailed recordings of calling males, including call amplitude, vocal sac volume and water ripple height, in 54 frogs (2430 calls). We found that all three measures correlated, with the strongest association between the vocal sac volume and call amplitude. We also found that multimodal models predicted the mass of calling males better than unimodal models. These results demonstrate how multimodal components of a communication system relate to each other and provide an important foundation for future studies on how receivers integrate and compare complex displays.

The crust of a male: does size matter when females are fertile?

Mammalian odors are frequently sexually dimorphic, with males often exhibiting a stronger, or otherwise distinct, odor relative to females, which can be especially useful for nocturnal species with reduced use of vision. Some male bats exhibit intense odors to attract females and reproduce, presumably as a consequence of a high concentration of testosterone. This usually coincides with the fertile period of females, which can be difficult to recognize visually because female mammals rarely advertise their precise reproductive condition. Recently, a novel odorous crust was discovered on the forearms of adult male fringe-lipped bats, Trachops cirrhosus. To understand its reproductive significance, we explored potential relationships between the size of the crust and testosterone concentration, testes size, female reproductive state, ectoparasite load, and body condition. We sampled bats during the mating season and determined crust size, testosterone concentration (plasma), testes volume, precise reproductive status of females (vaginal smears), body condition (ratio of body mass and forearm length), and ectoparasite load. Crust size (0–38 mm2) was positively correlated both to testosterone concentration (0.7–36.4 ng mL−1) and to relative testes volume (6.3–349.1 mm3). During the sampling period, vaginal smears confirmed that all females were in estrus. Ectoparasite load in males was significantly lower than in females, although both sexes were in similar body condition. Our results suggest that testosterone concentration is a key factor in the exhibition of a larger crust and presumably a stronger odorous signal to estrus females during the reproductive season. Male secondary sexual characteristics are critical for attracting females for mating. Male odor, in particular, can be indispensable in nocturnal species, as visual signals may lose their effectiveness under dark conditions. The most important male hormone, testosterone, increases the development of male exclusive traits, including odors. In the Neotropics, reproductive male fringe-lipped bats exhibit large odorous crusts on their forearms. The largest male crusts correspond with the highest concentration of testosterone, a relationship we find in the mating season, when vaginal smears confirm females are fertile. We also show that males with crusts have low ectoparasite loads. Our results suggest that the male crust could potentially reveal critical information. Our research highlights the significance of testosterone in the expression of male exclusive traits.

Sensory ecology of the frog-eating bat, Trachops cirrhosus, from DNA metabarcoding and behavior

Abstract Metabarcoding of prey DNA from fecal samples can be used to design behavioral experiments to study the foraging behavior and sensory ecology of predators. The frog-eating bat, Trachops cirrhosus, eavesdrops on the mating calls of its anuran prey. We captured wild T. cirrhosus and identified prey remains in the bats’ fecal samples using DNA metabarcoding of two gene regions (CO1 and 16S). Bats were preying on frogs previously unknown in their diet, such as species in the genus Pristimantis, which occurred in 29% of T. cirrhosus samples. Twenty-three percent of samples also contained DNA of Anolis lizards. We additionally report apparently rare predation events on hummingbirds and heterospecific bats. We used results from metabarcoding to design acoustic and 3D model stimuli to present to bats in behavioral experiments. We show predatory responses by T. cirrhosus to the calls of the frog Pristimantis taeniatus and to the rustling sounds of anoles moving through leaf-litter, as well as attacks on a stuffed hummingbird and a plastic anole model. The combination of species-specific dietary information from metabarcoding analyses with behavioral responses to prey cues provides a unique window into the foraging ecology of predators that are difficult to observe in the wild.

When the Hunter Becomes the Hunted: Foraging Bat Attacked by Pit Viper at Frog Chorus

The relationship between the fringe-lipped bat (Trachops cirrhosus) and the túngara frog (Engystomops pustulosus) has become a model for the study of predator–prey interactions. It has been hypothesized that T. cirrhosus faces risks as a bat whose foraging behavior brings it in regular contact with the ground. Our observation of a fer-de-lance (Bothrops asper) eating a bat (likely T. cirrhosus) at a túngara frog chorus suggests support of this hypothesis. We examine this interaction through the lens of the Landscape of Fear model, and postulate that bats must simultaneously navigate landscapes of fear and opportunity as they forage. These photographs illustrate the article “When the hunter becomes the hunted: foraging bat attacked by pit viper at frog chorus” by Hubert A. Szczygieł, and Rachel A. Page published in Ecology. https://doi.org/10.1002/ecy.3111.

Co-occurrence of Ectoparasites (Insecta and Arachnida) on Bats (Chiroptera) in an Atlantic Forest Remnant, Southeastern Brazil.

Neotropical bats are infested by multiple ectoparasites (like bat fly and mite species) and investigations on these invertebrates on their hosts are crucial to better understand the ectoparasite-ectoparasite and ectoparasite-host associations. The goal of this study was to report ectoparasites species (bat flies and mites) on bats, emphasizing ectoparasite co-occurrences and host-ectoparasite associations. We also test if there is relationship between bat flies and mites on their hosts. This study occurred twice a month from September 2011 to September 2012 in an Atlantic Forest remnant in Rio de Janeiro State, Brazil. Spearman correlation was used to test relationship between bat flies and mites. We found 27 species of ectoparasites on 13 species of bats. Ectoparasites belonged to the bat fly families Streblidae and Nycteribiidae, and the mite families Spinturnicidae, Macronyssidae, Sarcoptidae, and Trombiculidae. Streblid-streblid association was more frequent, but we also recorded streblid-spinturnicid, streblid-sarcoptid and spinturnicid-spinturnicid associations. The abundance of spinturnicid species was negatively related to the abundance of streblid species. We record the first occurrence of Strebla chrotopteri associated with Chrotopterus auritus, Periglischrus paracutisternus associated with Trachops cirrhosus and Basilia juquiensis associated with Myotis riparius for Rio de Janeiro State. There were several co-occurrences between different taxa and between species of the same family. These results show the importance of the integrated taxonomic record. The negative interspecific interactions between spinturnicid and streblid may affect distributions, structuring ectoparasite communities on hosts.

Social structure and relatedness in the fringe-lipped bat (Trachops cirrhosus).

General insights into the causes and effects of social structure can be gained from comparative analyses across socially and ecologically diverse taxa, such as bats, but long-term data are lacking for most species. In the neotropical fringe-lipped bat, Trachops cirrhosus, social transmission of foraging behaviour is clearly demonstrated in captivity, yet its social structure in the wild remains unclear. Here, we used microsatellite-based estimates of relatedness and records of 157 individually marked adults from 106 roost captures over 6 years, to infer whether male and female T. cirrhosus have preferred co-roosting associations and whether such associations were influenced by relatedness. Using a null model that controlled for year and roosting location, we found that both male and female T. cirrhosus have preferred roosting partners, but that only females demonstrate kin-biased association. Most roosting groups (67%) contained multiple females with one or two reproductive males. Relatedness patterns and recapture records corroborate genetic evidence for female philopatry and male dispersal. Our study adds to growing evidence that many bats demonstrate preferred roosting associations, which has the potential to influence social information transfer.

State-dependent learning influences foraging behaviour in an acoustic predator

Humans and other animals have been shown to exhibit preferences for options previously associated with greater past need. Such studies indicate that animals are sensitive to both the physical properties of choices and their own state-dependent gains at the time of learning. Because this behaviour appears to occur across divergent taxonomic groups, it most likely reflects a common way that animals learn about food. Here we study this phenomenon in the frog-eating bat, Trachops cirrhosus. This carnivorous bat hunts by eavesdropping on frog and insect mating calls and its diet is both broad and seasonally variable. As a result, these bats must learn about new sources of food and possibly the state-dependent gains associated with those sources. In this experiment we trained bats to associate two different acoustic cues (ringtones) to two identical food rewards. Each ringtone was encountered in one of two nutritional states: hungry or pre-fed. We then tested preferences between these cues under both nutritional states. We found that bats overwhelmingly preferred the ringtone associated with previous greater deprivation regardless of their condition during testing. We argue that it is most likely adaptive for frog-eating bats to place a higher value on food rewards that are obtained when internal reserves are low.

First record of pigmentation disorder in the Fringe-lipped Bat Trachops cirrhosus (Spix, 1823) (Chiroptera: Phyllostomidae) from southeast Brazil.

Piebaldism is a genetic pigmentation disorder, which is caused by absence of melanocytes in parts of the skin and/or hair follicles, with eyes and claws normally pigmented. The occurrence of piebaldism in natural populations is rare and the effects on fitness are still unknown. This article reports the first case of pigmentation disorders in the Fringe-lipped Bat Trachops cirrhosus (Spix, 1823) (Chiroptera: Phyllostomidae) caught in Barra do Triunfo, city of João Neiva, northeastern state of Espírito Santo, southeast Brazil.

Effects of information load on response times in frogs and bats: mate choice vs. prey choice

Decisions tend to become more challenging as the number of available options increases and choice sets become more complex. Choosing between multiple options may require additional information processing time and effort. Here, we asked if response time increases with stimulus number and attractiveness by female frogs (Physalaemus pustulosus) and their predators, frog-eating bats (Trachops cirrhosus), when comparing the mating calls of male tungara frogs. We found that frogs’ response time is significantly longer when presented with two calls, compared with one. Bats also take longer to respond when presented with two calls but only when they were complex calls. Although the frogs and bats behave somewhat similarly in this experiment, the decisions that these animals are making are occurring in different domains (mating vs. foraging) and have different fitness consequences. Given these differences, we find it especially interesting that for both frogs and bats, we see similar temporal patterns in response times as a function of information load. SIGNIFICANCE STATEMENT: Animals are often faced with several options simultaneously. One cost of decision-making is the time involved in choosing the best option within a choice set. Here, we asked whether female frogs and frog-eating bats take longer to respond when presented multiple frog mating calls simultaneously. We also asked whether the attractiveness of those frog calls influences the time it takes frogs and bats to respond to them. We found that the time to respond was influenced by both the number and attractiveness of frog calls for both bats and frogs; however, frog response time seemed to be more greatly influenced by the number of frog calls, while bat response time seemed to be more influenced by the attractiveness of frog calls. In general, our results suggest that there may be similar mechanisms involved in decision-making for both animals.