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Fishing and echolocation behavior of the greater bulldog bat, Noctilio leporinus, in the field
Abstract
When hunting for fish Noctilio leporinus uses several strategies. In high search flight it flies within 20–50 cm of the water surface and emits groups of two to four echolocation signals, always containing at least one pure constant frequency (CF) pulse and one mixed CF-FM pulse consisting of a CF component which is followed by a frequency-modulated (FM) component. The pure CF signals are the longest, with an average duration of 13.3 ms and a maximum of 17 ms. The CF component of the CF-FM signals averages 8.9 ms, the FM sweeps 3.9 ms. The CF components have frequencies of 52.8–56.2 kHz and the FM components have an average bandwidth of 25.9 kHz. A bat in high search flight reacts to jumping fish with pointed dips at the spot where a fish has broken the surface. As it descends to the water surface the bat shows the typical approach pattern of all bats with decreasing pulse duration and pulse interval. A jumping fish reveals itself by a typical pattern of temporary echo glints, reflected back to the bat from its body and from the water disturbance. In low search flight N. leporinus drops to a height of only 4–10 cm, with body parallel to the water, legs extended straight back and turned slightly downward, and feet cocked somewhat above the line of the legs and poised within 2–4 cm of the water surface. In this situation N. leporinus emits long series of short CF-FM pulses with an average duration of 5.6 ms (CF 3.1 and FM 2.6) and an average pulse interval of 20 ms, indicating that it is looking for targets within a short range. N. leporinus also makes pointed dips during low search flight by rapidly snapping the feet into the water at the spot where it has localized a jumping fish or disturbance. In the random rake mode, N. leporinus drops to the water surface, lowers its feet and drags its claws through the water in relatively straight lines for up to 10m. The echolocation behavior is similar to that of high search flight. This indicates that in this hunting mode N. leporinus is not pursuing specific targets, and that raking is a random or statistical search for surface fishes. When raking, the bat uses two strategies. In directed random rake it rakes through patches of water where fish jumping activity is high. Our interpretation is that the bat detects this activity by echolocation but prefers not to concentrate on a single jumping fish. In the absence of jumping fish, after flying for several minutes without any dips, N. leporinus starts to make very long rakes in areas where it has hunted successfully before (memory-directed random rake). Hunting bats caught a fish approximately once in every 50–200 passes through the hunting area.
... Even though this foraging technique cannot be fully discounted, the specialized fishtargeted behavior observed in different studies indicates that fishing without stimuli is improbable in M. capaccinii. Memory-directed random rake foraging by the large piscivorous bat Noctilio leporinus has been reported in areas where fish stimuli were not present at the time, but where fish were successfully hunted previously (Schnitzler et al. 1994). While N. leporinus can perform long dips to scan a large area seeking prey underwater (Schnitzler et al. 1994), the light weight and small claws of M. capaccinii, as well as its morphological wing features, may prevent it from using the same strategy . ...
... Memory-directed random rake foraging by the large piscivorous bat Noctilio leporinus has been reported in areas where fish stimuli were not present at the time, but where fish were successfully hunted previously (Schnitzler et al. 1994). While N. leporinus can perform long dips to scan a large area seeking prey underwater (Schnitzler et al. 1994), the light weight and small claws of M. capaccinii, as well as its morphological wing features, may prevent it from using the same strategy . ...
... When fishing, the uropatagium is also submerged into the water, as reported for Myotis vivesi (Altenbach 1989). Unlike Noctilio leporinus (Schnitzler et al. 1994), the two small Myotis bats are unable to fold the interfemoral membrane up and forward, which entails an increased friction with water and could be one of the main features constraining catchable fish size. In fact, the longer and deeper dip performed when fishing entails a greater loss of flight speed than when hunting insects. ...
This comprehensive species-specific chapter covers all aspects of the mammalian biology, including paleontology, physiology, genetics, reproduction and development, ecology, habitat, diet, mortality, and behavior. The economic significance and management of mammals and future challenges for research and conservation are addressed as well. The chapter includes a distribution map, a photograph of the animal, and a list of key literature.
... When foraging for insects sitting on or flying close to duckweed or rippled water, bats have difficulty perceiving prey as the prey echo is buried in clutter echoes (Boonman et al. 1998). The two species of bulldog bats (Noctilionidae), one of which, Noctilio leporinus, is well known for its fishing habits (Schnitzler et al. 1994, Kalko andSchnitzler 1998), also forage for insects close to or drifting on the water surface while emitting high-intensity CF and CF-FM signals of medium duration that are rather similar to the QCF-FM signals of mormoopid bats. ...
... In a few cases, bats do not use echolocation or other sensory cues directly to find distant prey but screen known or presumed feeding sites based on previous experience. Accordingly, these bats forage in a random mode (Schnitzler et al. 1994, Schnitzler andKalko 1998). ...
... There is no evidence for an effect of wind on (F) decision probability (f 3 ) and decision time (t 3 ). Wind is likely to affect (G) pursuit probability (f 4 ) and pursuit time (t 4 ) due to its impact on flight speed and flight costs while trawling for the detected fish (Schnitzler et al., 1994). (H) Subjugation is a rapid process in fishing bats, making it unlikely that its probability (f 5 ) and duration (t 5 ) are affected by wind (Altenbach, 1989). ...
Understanding the factors that determine the occurrence and strength of ecological interactions under specific abiotic and biotic conditions is fundamental since many aspects of ecological community stability and ecosystem functioning depend on patterns of interactions among species. Current approaches to mapping food webs are mostly based on traits, expert knowledge, experiments, and/or statistical inference. However, they do not offer clear mechanisms explaining how trophic interactions are affected by the interplay between organism characteristics and aspects of the physical environment, such as temperature, light intensity or viscosity. Hence, they cannot yet predict accurately how local food webs will respond to anthropogenic pressures, notably to climate change and species invasions. Herein, we propose a framework that synthesises recent developments in food‐web theory, integrating body size and metabolism with the physical properties of ecosystems. We advocate for combination of the movement paradigm with a modular definition of the predation sequence, because movement is central to predator–prey interactions, and a generic, modular model is needed to describe all the possible variation in predator–prey interactions. Pending sufficient empirical and theoretical knowledge, our framework will help predict the food‐web impacts of well‐studied physical factors, such as temperature and oxygen availability, as well as less commonly considered variables such as wind, turbidity or electrical conductivity. An improved predictive capability will facilitate a better understanding of ecosystem responses to a changing world.
... Here, N. leporinus has been documented only in habitats with woodland characteristics (GR), this can be attributed to the increased presence of bodies of water and public lighting in their vicinity. The proximity of water in these habitats may play a crucial role, as N. leporinus primarily, though not exclusively, feeds on small fish (Schnitzler et al. 1994). Furthermore, this bat can supplement its diet with insects (Goodwin 1928;Brooke 1994), which are attracted to the streetlights during its foraging activities (Zortéa and Aguiar 2001). ...
Impacts of urbanization can affect bat species differently, some bat assemblages demonstrated differences in their activity and richness between forest environments and urban areas. Bats species can seek refuge in green areas (urban forest remnants, parks and groves) or in buildings within the urban landscape. Using bioacoustics, we examined habitat use of by non-phyllostomid bats in a large Metropolitan Region of João Pessoa-PB, northeastern Brazil, comparing the activity and species/sonotypes composition of bat assemblages documented in Atlantic Forest remnants (FF) with those in the urbanized matrix areas (UM). Fifteen species belonging to four families were recorded. Out of these records, 11 were documented in both UM and FF, while Neoplatymops mattogrossensis, Myotis cf. riparius, and Rhynchonycteris naso were exclusively found in FF, and Promops nasutus (first record for the state) was only found in UM. The richness and activity of bats differed between FF and UM. Molossops temminckii and Promops nasutus were observed solely in arboreal habitats, whether in the forest fragments or in the UM areas. Only Cynomops planirostris, Eumops sp., Molossus molossus, Molossus rufus, and Promops centralis were recorded in strictly urban habitats, and they did not show differences in activities between FF and UM. These results indicate the ability of these bats to adapt to structural habitat changes within an urban matrix, reaching the highest levels of synanthropy. Our results demonstrate that the impact of urbanization on bat assemblages can be mitigated by maintaining green areas within an urban matrix.
... As part of their ecological adaptations for diverse foraging modes, these bats have evolved nearly the full range of bat echolocation call types, such as constant frequency, short broadband multiharmonic, narrowband multiharmonic, and short broadband fundamental harmonic (Davies, Bates, et al., 2013;Jones et al., 2013;Jones & Teeling, 2006;Sulser et al., 2022;Thiagavel et al., 2018). They also vary in their reliance on echolocation, vision, and olfaction (Gracheva et al., 2011;Sadier et al., 2018;Schnitzler et al., 1994;Thies et al., 1998). As cochleae are initiated and develop early during development (Basch et al., 2016;Driver & Kelley, 2020;Groves & Fekete, 2012), their development might play a pivotal role in the ontogeny of the other sensory systems, consistent with a tradeoff hypothesis. ...
Sensory organs must develop alongside the skull within which they are largely encased, and this relationship can manifest as the skull constraining the organs, organs constraining the skull, or organs constraining one another in relative size. How this interplay between sensory organs and the developing skull plays out during the evolution of sensory diversity; however, remains unknown. Here, we examine the developmental sequence of the cochlea, the organ responsible for hearing and echolocation, in species with distinct diet and echolocation types within the ecologically diverse bat super‐family Noctilionoidea. We found the size and shape of the cochlea largely correlates with skull size, with exceptions of Pteronotus parnellii , whose high duty cycle echolocation (nearly constant emission of sound pulses during their echolocation process allowing for detailed information gathering, also called constant frequency echolocation) corresponds to a larger cochlear and basal turn, and Monophyllus redmani , a small‐bodied nectarivorous bat, for which interactions with other sensory organs restrict cochlea size. Our findings support the existence of developmental constraints, suggesting that both developmental and anatomical factors may act synergistically during the development of sensory systems in noctilionoid bats.
... We had a relatively high number of captured individuals of Noctilio leporinus, so we had a good representation of individuals recorded in the database. The calls of these fishing bats are typically long, with an initial constant frequency segment (54 kHz), followed by a frequency-modulated (FM) component; this type of calls is usually emitted on the surface of the water for the search of prey at relatively short ranges (Hartley, 1989;Schnitzler, Kalko, Kaipf, & Grinnell, 1994). We could not collect any individual for Noctilio albiventris. ...
... The fishing bat uses short-CF/FM echolocation pulses that detects water surface disturbances such as ripples or exposed fish fins (Wenstrup and Suthers 1984). It has external adaptations to piscivory, such as greatly elongated feet, large and laterally compressed claws, and cheek pouches used to store food while foraging (Altenbach 1989;Hood and Jones 1984;Kalko et al. 1998;Schnitzler et al. 1994). Morphological traits of the feet and claws have been related to trawling behaviour to capture prey, especially fish, over water (Aizpurua and Alberdi 2018), while cheek pouches may allow bats to fish continuously at their feeding sites (Hood and Jones 1984). ...
We report feeding behaviour, dates of peak reproduction, and sexual size dimorphism of the fishing bat, Noctilio leporinus, in the Gulf of Mexico. For the first time we document the size of cheek pouches in N. leporinus and fish species consumed in the water bodies of southern Mexico and analyse differences in wing morphology and biomechanical flight descriptors between the sexes. We found sexual dimorphism in size for most of the external measurements but not in wing characters. This species can consume prey up to a third of its size. We confirmed the presence of N. leporinus in localities in Tabasco, Mexico 60 years after the first report.
Thirteen years have gone by since the first international meet ing on Animal Sonar Systems was held in Frascati, Italy, in 1966. Since that time, almost 900 papers have been published on its theme. The first symposium was vital as it was the starting point for new research lines whose goal was to design and develop technological systems with properties approaching optimal biological systems. There have been highly significant developments since then in all domains related to biological sonar systems and in their appli cations to the engineering field. The time had therefore come for a multidisciplinary integration of the information gathered, not only on the evolution of systems used in animal echolocation, but on systems theory, behavior and neurobiology, signal-to-noise ratio, masking, signal processing, and measures observed in certain species against animal sonar systems. Modern electronics technology and systems theory which have been developed only since 1974 now allow designing sophisticated sonar and radar systems applying principles derived from biological systems. At the time of the Frascati meeting, integrated circuits and technol ogies exploiting computer science were not well enough developed to yield advantages now possible through use of real-time analysis, leading to, among other things, a definition of target temporal char acteristics, as biological sonar systems are able to do. All of these new technical developments necessitate close co operation between engineers and biologists within the framework of new experiments which have been designed, particularly in the past five years.
Microchiropteran bats emit echolocation sounds that have structured patterns of frequency changes over time. Classes of frequency pattern have been observed among bat orientation pulses. Bat echolocation sounds generally consist of constant frequency (CF) and frequency modulated (FM) elements alone or in a combination of the two components. For example, in certain species (known as CF/FM bats), the echolocation sounds contain a CF component preceding the FM sweep; in some species the CF component is short (under 12 msec), while in others it is long (over 12 msec). The defined structures of echolocation sounds presumably reflex specific information processing requirements. One generally accepted requirement is that a broadband signal is necessary for accurate perception of target distance by neural measurement of the time interval between the emitted broadband event and a returning echo. Nevertheless, the essential elements and processing requirements of complex CF/FM echolocation sounds has mostly been a matter of conjecture. In this paper I describe experiments that demonstrate which structural elements of complex CF/FM echolocation sounds code target distance information and provide a mechanism regarding hcw this information is processed by the nervous system. These studies suggest that CF/FM bats use both the CF and FM components of their CF/FM echolocation sounds for the determination of target distance, with the onset of the CF component activating a gating mechanism that establishes a time window during which FM component pulse-echo pairs are processed for distance information.
The various species of bats analyze the acoustical parameters of their orientation sounds in order to detect and localize targets. Behavioral studies indicate that echolocation also enables bats to obtain information on other target features which they can use to distinguish different targets and perhaps even to identify behaviorally relevant targets (summarized in Schnitzler and Henson 1980).
Bats hunting by sonar do not receive continuous target information; rather, the echo from each sonar pulse provides an acoustic bulletin by which they update their current perception of target range and position. This suggests that a hunting bat might keep track of moving prey by two general techniques. It might simply fly toward the last known position of the target (a non-predictive tracking strategy), or.t could somehow predict the target’s trajectory on the basis of known target parameters such as velocity, acceleration and position at.the time of the most recent echo (a predictive strategy).
Animals living in the dark are faced with the problem that vision is only of limited use for orientation in the environment and for the detection and identification of relevant targets. In order to cope with this situation, some animals, during evolution, developed eyes which were especially adapted for good visual efficiency at low light intensities whereas others improved the remaining sensory systems.