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Stridulation is used by male katydids to produce sound via the rubbing together of their specialised forewings, either by sustained or interrupted sweeps of the file producing different tones and call structures. There are many species of Orthoptera that remain undescribed and their acoustic signals are unknown. This study aims to measure and quantify the mechanics of wing vibration, sound production and acoustic properties of the hearing system in a new genus of Pseudophyllinae with taxonomic descriptions of two new species. The calling behaviour and wing mechanics of males were measured using micro-scanning laser Doppler vibrometry, microscopy, and ultrasound sensitive equipment. The resonant properties of the acoustic pinnae of the ears were obtained via µ-CT scanning and 3D printed experimentation, and numerical modelling was used to validate the results. Analysis of sound recordings and wing vibrations revealed that the stridulatory areas of the right tegmen exhibit relatively narrow frequency responses and produce narrowband calls between 12 and 20 kHz. As in most Pseudophyllinae, only the right mirror is activated for sound production. The acoustic pinnae of all species were found to provide a broadband increased acoustic gain from ~40-120 kHz by up to 25 dB, peaking at almost 90 kHz which coincides with the echolocation frequency of sympatric bats. The new genus, named Satizabalus n. gen., is here derived as a new polytypic genus from the existing genus Gnathoclita, based on morphological and acoustic evidence from one described (S. sodalis n. comb.) and two new species (S. jorgevargasi n. sp. and S. hauca n. sp.). Unlike most Tettigoniidae, Satizabalus exhibits a particular form of sexual dimorphism whereby the heads and mandibles of the males are greatly enlarged compared to the females. We suggest that Satizabalus is related to the genus Trichotettix, also found in cloud forests in Colombia, and not to Gnathoclita.
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Ortópteros , Asas de Animais , Animais , Masculino , Asas de Animais/fisiologia , Asas de Animais/anatomia & histologia , Colômbia , Ortópteros/fisiologia , Ortópteros/anatomia & histologia , Comunicação Animal , Florestas , Vocalização Animal/fisiologia , Acústica , Feminino , VibraçãoRESUMO
Bats frequently feed over water bodies, but the net value of the water bodies depends on characteristics such as the amount of physical clutter the water body has. More physical clutter may reduce the detection of prey by bats and may also increase energetic costs by increasing in the number of obstacles to avoid. Consequently, we hypothesized that increasing physical clutter affected the use of an artificial pond where the Lesser Bulldog Bat Noctilio albiventris, a Neotropical fishing bat, forages regularly over water. We experimentally tested this idea recording the number of passes and feeding buzzes emitted by the bats on different nights when we added two levels of obstacles over the water and on control nights with no obstacles. We only found differences between the treatment with the highest obstacle density and the control; there were fewer passes and less feeding buzzes with more obstacles. Therefore, the addition of obstacles did affect the foraging behavior of N. albiventris. Furthermore, we suggest that increasing physical clutter, as in our experiments, may be a cost-effective way to reduce conflicts between local fisher farmers and fishing bats in Neotropical rural areas.(AU)
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Animais , Comportamento Animal , Quirópteros , PesqueirosRESUMO
Acoustic monitoring in cetacean studies is an effective but expensive approach. This is partly because of the high sampling rate required by acoustic devices when recording high-frequency echolocation clicks. However, the proportion of echolocation clicks recorded at different frequencies is unknown for many species, including bottlenose dolphins. Here, we investigated the echolocation clicks of two subspecies of bottlenose dolphins in the western South Atlantic Ocean. The possibility of recording echolocation clicks at 24 and 48 kHz was assessed by two approaches. First, we considered the clicks in the frequency range up to 96 kHz. We found a loss of 0.95-13.90% of echolocation clicks in the frequency range below 24 kHz, and 0.01-0.42% below 48 kHz, to each subspecies. Then, we evaluated these recordings downsampled at 48 and 96 kHz and confirmed that echolocation clicks are recorded at these lower frequencies, with some loss. Therefore, despite reaching high frequencies, the clicks can also be recorded at lower frequencies because echolocation clicks from bottlenose dolphins are broadband. We concluded that ecological studies based on the presence-absence data are still effective for bottlenose dolphins when acoustic devices with a limited sampling rate are used.
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Echolocation clicks can reflect the anatomy of the vocalizing animal, enabling the distinction of species. River dolphins from the family Iniidae are formally represented by one species and two subspecies (Inia geoffrensis geoffrensis and I. g. humboldtiana). Additionally, two other species have been proposed (I. boliviensis and I. araguaiaensis) regarding its level of restricted distribution and morph-genetics differences. For the Committee on Taxonomy of the Society for Marine Mammalogy, the specific status of the proposed species relies on further knowledge on morphology, ecology, and genetics. Given that species-specific status is required for conservation efforts, we described and compared the echolocation clicks of Inia spp., searching for specific differences on their vocalizations. The sounds were captured with a Cetacean Research ™ C54XRS (+3/-20 dB, -185 dB re: 1V/µPa) in Guaviare River (Orinoco basin), Madeira River (Madeira basin), Xingu River (Amazon Basin), and Araguaia River (Tocantins-Araguaia basin). We found significant differences in all analyzed parameters (peak frequency, 3 dB bandwidth, 10 dB bandwidth and inter-click interval) for all species and subspecies. Differences in acoustical parameters of clicks are mainly related to the animal's internal morphology, thus this study may potentially support with information for the species-level classification mostly of I. araguaiaensis (the Araguaian boto). Classifying the Araguaian boto separately from I. geoffrensis has important implications for the species in terms of conservation status, since it is restricted to a highly impacted river system.
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In Honduras, most bat inventories have been carried out with mist nets as the main sampling method, skewing knowledge towards the Phyllostomidae family, therefore the diversity and distribution of insectivorous bats is underrepresented. In order to have a more complete knowledge of the diversity of bats in the municipality of Yuscarán and mainly in the Yuscarán Biological Reserve, an inventory was carried out using the techniques of mist-netting and acoustic monitoring. The samplings were carried out between 910 and 1,827 m.a.s.l., covering agroecosystems, broadleaf forest, pine forest and urban environment. A total of 32 species of bats were registered, which represents 28% of the species diversity present in Honduras. Species belonging to five families were recorded: Emballonuridae (6.25%), Mormoopidae (15.22%), Phyllostomidae (56.25%), Molossidae (9.37%) and Vespertilionidae (12.5%). With the mist nets, a sampling effort of 7,128 m²/h was reached, which allowed the capture of 20 species and 186 individuals. Through the acoustic method, with 84 h/r, 13 species of insectivorous bats were recorded. The values of the acoustic parameters analysed from the search phase of each insectivorous species are provided, which can serve as a reference for the identification of species from Hondurans. To advance our understanding of the distribution patterns, composition, and vocal signatures of insectivore bats, we suggest the complementary use of mist nets and acoustic recorders in the inventories.(AU)
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Animais , Quirópteros/classificação , Acústica , Eulipotyphla , EcologiaRESUMO
Head morphology in toothed whales evolved under selective pressures on feeding strategy and sound production. The postnatal development of the skull (n = 207) and mandible (n = 219) of six Delphinida species which differ in feeding strategy but exhibit similar sound emission patterns, including two narrow-band high-frequency species, were investigated through 3D morphometrics. Morphological changes throughout ontogeny were demonstrated based on the main source of variation (i.e., prediction lines) and the common allometric component. Multivariate trajectory analysis with pairwise comparisons between all species was performed to evaluate specific differences on the postnatal development of skulls and mandibles. Changes in the rostrum formation contributed to the variation (skull: 49%; mandible: 90%) of the entire data set and might not only reflect the feeding strategy adopted by each lineage but also represents an adaptation for sound production and reception. As an important structure for directionality of sound emissions, this may increase directionality in raptorial feeders. Phylogenetic generalized least squares analyses indicated that shape of the anterior portion of the skull is strongly dependent on phylogeny and might not only reflect feeding mode, but also morphological adaptations for sound production, particularly in raptorial species. Thus, postnatal development seems to represent a crucial stage for biosonar maturation in some raptorial species such as Pontoporia blainvillei and Sousa plumbea. The ontogeny of their main tool for navigation and hunting might reflect their natural history peculiarities and thus potentially define their main vulnerabilities to anthropogenic changes in the environment.
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Golfinhos/anatomia & histologia , Ingestão de Alimentos/fisiologia , Ecolocação/fisiologia , Cabeça/anatomia & histologia , Animais , Evolução Biológica , Golfinhos/fisiologia , Mandíbula/anatomia & histologia , Filogenia , Crânio/anatomia & histologiaRESUMO
Abstract In Honduras, most bat inventories have been carried out with mist nets as the main sampling method, skewing knowledge towards the Phyllostomidae family, therefore the diversity and distribution of insectivorous bats is underrepresented. In order to have a more complete knowledge of the diversity of bats in the municipality of Yuscarán and mainly in the Yuscarán Biological Reserve, an inventory was carried out using the techniques of mist-netting and acoustic monitoring. The samplings were carried out between 910 and 1,827 m.a.s.l., covering agroecosystems, broadleaf forest, pine forest and urban environment. A total of 32 species of bats were registered, which represents 28% of the species diversity present in Honduras. Species belonging to five families were recorded: Emballonuridae (6.25%), Mormoopidae (15.22%), Phyllostomidae (56.25%), Molossidae (9.37%) and Vespertilionidae (12.5%). With the mist nets, a sampling effort of 7,128 m²/h was reached, which allowed the capture of 20 species and 186 individuals. Through the acoustic method, with 84 h/r, 13 species of insectivorous bats were recorded. The values of the acoustic parameters analysed from the search phase of each insectivorous species are provided, which can serve as a reference for the identification of species from Hondurans. To advance our understanding of the distribution patterns, composition, and vocal signatures of insectivore bats, we suggest the complementary use of mist nets and acoustic recorders in the inventories.
RESUMO
Abstract In Honduras, most bat inventories have been carried out with mist nets as the main sampling method, skewing knowledge towards the Phyllostomidae family, therefore the diversity and distribution of insectivorous bats is underrepresented. In order to have a more complete knowledge of the diversity of bats in the municipality of Yuscarán and mainly in the Yuscarán Biological Reserve, an inventory was carried out using the techniques of mist-netting and acoustic monitoring. The samplings were carried out between 910 and 1,827 m.a.s.l., covering agroecosystems, broadleaf forest, pine forest and urban environment. A total of 32 species of bats were registered, which represents 28% of the species diversity present in Honduras. Species belonging to five families were recorded: Emballonuridae (6.25%), Mormoopidae (15.22%), Phyllostomidae (56.25%), Molossidae (9.37%) and Vespertilionidae (12.5%). With the mist nets, a sampling effort of 7,128 m²/h was reached, which allowed the capture of 20 species and 186 individuals. Through the acoustic method, with 84 h/r, 13 species of insectivorous bats were recorded. The values of the acoustic parameters analysed from the search phase of each insectivorous species are provided, which can serve as a reference for the identification of species from Hondurans. To advance our understanding of the distribution patterns, composition, and vocal signatures of insectivore bats, we suggest the complementary use of mist nets and acoustic recorders in the inventories.
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Baseline knowledge of spatial and temporal distribution patterns is essential for cetacean management and conservation. Such knowledge is particularly important in areas where gillnet fishing occurs, as the Upper Gulf of California, which increases the probability of bycatch of cetaceans. In this area, the vaquita porpoise (Phocoena sinus) has been widely studied, but the knowledge of other cetaceans is scarce and based on traditional visual survey methods. We used data collected by an array of acoustic click detectors (C-PODs) during the summers 2011 to 2015 to analyze the distribution of dolphins in the Vaquita Refuge in the Upper Gulf of California. We recorded 120,038 echolocation click trains of dolphins during 12,371 days of recording effort at 46 sampling sites. Based on simultaneous visual and acoustic data, we estimated a false positive acoustic detection rate of 19.4%. Dolphin acoustic activity varied among sites, with higher activity in the east of the Vaquita Refuge. Acoustic activity was higher at night than during the day. We used negative binomial generalized linear models to study the count of clicks of dolphins in relation to spatial, temporal, physical, biological and anthropogenic explanatory variables. The best model selected for the response variable included sampling site, day-night condition, and vertical component of tide speed. Patterns in the spatial distribution of predicted acoustic activity of dolphins were similar to the acoustic activity observed per sampling season. Higher acoustic activity was predicted at night, but the tide speed variable was not relevant under this condition. Acoustic activity patterns could be related to the availability of prey resources since echolocation click trains are associated with foraging activities of dolphins. This is the first study of the distribution of dolphins in Mexico using medium-term systematic passive acoustic monitoring, and the results can contribute to better management to the natural protected area located in the Upper Gulf of California.
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Abstract: Thyropteridae is a family of bats endemic to the Neotropical region, and Thyroptera devivoi is the only species in the family that occurs exclusively in forest patches within savannas of northern South America and north of the Brazilian Cerrado. Primary data on the species are still scarce. Therefore, in this study our objective was to fill knowledge gaps on geographical distribution, roost-use, and echolocation for the species. We observed a T. devivoi colony of 15 individuals living under a dead palm leaf. The bats used the leaf as a roost for at least four days. After capturing one individual, we confirmed the species identification via skull size and the oblong shape of the adhesive disk. The new record reinforces the association of this species with non-forested formations, and its occurrence mainly in savannas. Echolocation calls of T. devivoi are consistent with those known for the genus, with multiharmonic, low intensity and high frequency pulses. Despite these new data, more studies are certainly needed to enhance distribution data for the species, as well as to clarify the biological and ecological requirements of the species.
Resumo: Thyropteridae é uma família de morcegos endêmica da região Neotropical e Thyroptera devivoi é a única espécie da família que ocorre exclusivamente em manchas florestais das savanas do norte de América do Sul e do Cerrado Brasileiro. Dados primários da espécie são ainda escassos e o objetivo deste estudo foi preencher lacunas de conhecimento sobre distribuição geográfica, uso de abrigos e padrões de ecolocalização da espécie. Nós observamos uma colônia de T. devivoi com 15 indivíduos vivendo sob uma folha morta de palmeira. Os morcegos usaram a folha como abrigo ao menos por quatro dias. Depois de capturar um indivíduo, nós confirmamos a identificação da espécie por meio da morfologia do crânio e do disco adesivo. O novo registro reforça a associação da espécie com formações não florestais e a ocorrência principalmente em savanas. Os chamados de ecolocalização de T. devivoi são consistentes com o conhecido para o gênero, com pulsos multi-harmônicos de baixa intensidade e alta frequência. A despeito destes novos dados, mais estudos são certamente necessários para aprimorar os dados de distribuição assim como os requerimentos biológicos da espécie.
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Las poblaciones insulares frecuentemente difieren de las continentales, en morfológica y comportamiento. Consecuentemente, utilizar características externas puede dificultar la identificación taxonómica de especies en las islas. En el Parque Nacional Natural Gorgona, particularmente, ha existido controversia sobre la identidad de varias especies de murciélagos residentes. Nuestro objetivo fue determinar la identidad taxonómica de la población de Saccopteryx de esta isla, que tiene la particularidad de tener actividad diurna. Evaluamos las diferencias entre las poblaciones mediante morfometría (tradicional y geométrica) y llamados de ecolocalización. Además, debido a que las especies difieren en su sistema de apareamiento, evaluamos la conformación de los grupos en los refugios. Pese a la variación en la morfometría craneal y los llamados de ecolocalización entre las poblaciones, la población de Gorgona fue más similar a S. leptura que a S. bilineata. Las conformaciones de los grupos en los refugios sugieren un sistema monógamo como en S. leptura. Por ende, concluimos que la especie de la isla es S. leptura. Adicionalmente, la historia biogeográfica y el aislamiento geográfico de la isla sugieren que esta población puede ser diferente de sus contrapartes continentales debido al efecto fundador, deriva genética y/o adaptaciones a las condiciones ambientales locales.
Insular populations can differ from their continental counterparts since they are subject to particular pressures, biotic and abiotic, that can lead to variations in morphology and behavior; thus, the use of external characters may complicate taxonomic identification of insular populations. Even though the bat assemblage of Gorgona Island is a conservation target, there has been controversy about the taxonomic identity of bats from this Colombian National Natural Park. Specifically, our goal was to determine the taxonomic identity of the population of the sac-winged bat (genus Saccopteryx) resident in Gorgona, which have the peculiarity of having diurnal activity. Thus, we assessed differences among populations using morphometrics (traditional and geometric) and echolocation calls. Additionally, since the species of Saccopteryx involved have different mating systems, we assessed roosting association of Gorgona population as a surrogate for mating system. Despite the variation in skull morphometrics and echolocation calls among populations, Gorgona population was more similar to S. leptura than to S. bilineata. Besides, evolutionary allometry was significant, but size explained a small proportion of shape differences among populations. Finally, roosting association of Gorgona population suggests a monogamous mating system such as in S. leptura. We conclude that Saccopteryx from Gorgona corresponds to S. leptura. In addition, biogeographic history and geographic isolation of the island suggest that this population may have differentiated from their mainland counterparts through founder effect, genetic drift and/or adaptation to the local biotic and abiotic environmental conditions.
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Background noise can have strong negative consequences for animals, reducing individual fitness by masking communication signals, impeding prey detection and increasing predation risk. While the negative impacts of noise across taxa have been well documented, the use of noise as an informational cue, providing animals with reliable information on environmental conditions, has been less well studied. In the tropical rainforest, downpours can be intense and frequent. Strong rainfall may impede efficient orientation and foraging for bats that need echolocation to both navigate and detect prey, and can result in higher flight costs due to increased metabolic rates. Using playback experiments at natural roosts, we tested whether two bat species, differing in their hunting strategies and foraging habitats, use rain noise as a cue to delay emergence from their roosts. We found that both species significantly delayed their emergence time during rain noise playbacks versus silence and ambient noise controls. We conclude that bats can use background noise, here the acoustic component of rainfall, as a reliable informational cue to make informed decisions, in this case about whether to initiate foraging trips or remain in the shelter of their roosts. Our findings suggest that environmental background noise can sometimes be beneficial to animals, in particular in situations where other sensory cues may be absent.
Assuntos
Quirópteros/fisiologia , Sinais (Psicologia) , Comportamento Alimentar , Voo Animal , Ruído , Animais , Tomada de Decisões , Panamá , Floresta Úmida , Especificidade da EspécieRESUMO
The macroscopic morphology of structures involved in sound generation in the Indian Ocean humpback dolphin (Sousa plumbea) were described for the first time using computed tomography imaging and standard gross dissection techniques. The Indian Ocean humpback dolphin may represent a useful comparative model to the bottlenose dolphin (Tursiops sp.) to provide insights into the functional anatomy of the sound production in dolphins, since these coastal dolphins exhibit similar body size and share similarities on acoustic behavior. The general arrangement of sound generating structures, that is, air sacs and muscles, was similar in both the bottlenose dolphin and the Indian Ocean humpback dolphin. The main difference between the two species existed in a small left posterior branch of the melon in the Indian Ocean humpback dolphin, which was not found in the bottlenose dolphin and might reflect an adaptation of directionality for high frequency communication sounds as seen in some other delphinids (e.g., Lagenorhynchus sp., Grampus griseus). Thus, this may be the main reason for the asymmetry of the sound production structures in dolphins. Additionally, the longer rostrum in Indian Ocean humpback dolphins might suggest a more directional echolocation beam compared to the Lahille's bottlenose dolphin. Anat Rec, 302:849-860, 2019. © 2018 Wiley Periodicals, Inc.
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Sacos Aéreos/anatomia & histologia , Golfinhos/fisiologia , Ecolocação/fisiologia , Músculo Esquelético/anatomia & histologia , Vocalização Animal , Sacos Aéreos/diagnóstico por imagem , Sacos Aéreos/fisiologia , Animais , Dissecação , Golfinhos/anatomia & histologia , Feminino , Cabeça/anatomia & histologia , Cabeça/diagnóstico por imagem , Oceano Índico , Masculino , Músculo Esquelético/diagnóstico por imagem , Especificidade da Espécie , Tomografia Computadorizada por Raios XRESUMO
BACKGROUND: The distinction between lineages of neotropical bats from the Pteronotus parnellii species complex has been previously made according to mitochondrial DNA, and especially morphology and acoustics, in order to separate them into two species. In these studies, either sample sizes were too low when genetic and acoustic or morphological data were gathered on the same individuals, or genetic and other data were collected on different individuals. In this study, we intensively sampled bats in 4 caves and combined all approaches in order to analyse genetic, morphologic, and acoustic divergence between these lineages that live in the same caves in French Guiana. RESULTS: A multiplex of 20 polymorphic microsatellite markers was developed using the 454-pyrosequencing technique to investigate for the first time the extent of reproductive isolation between the two lineages and the population genetic structure within lineages. We genotyped 748 individuals sampled between 2010 and 2015 at the 20 nuclear microsatellite loci and sequenced a portion of the cytochrome c oxydase I gene in a subset of these. Two distinct, non-overlapping haplogroups corresponding to cryptic species P. alitonus and P. rubiginosus were revealed, in accordance with previous findings. No spatial genetic structure between caves was detected for both species. Hybridization appeared to be quite limited (0.1-4%) using microsatellite markers whereas introgression was more common (7.5%) and asymmetric for mitochondrial DNA (mtDNA). CONCLUSIONS: The extremely low rate of hybridization could be explained by differences in life cycle phenology between species as well as morphological and acoustical distinction between sexes in one or the other species. Taken together, these results add to our growing understanding of the nature of species boundaries in Pteronotus parnelli, but deserve more in-depth studies to understand the evolutionary processes underlying asymmetric mtDNA introgression in this group of cryptic species.
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Acústica , Quirópteros/genética , Ecossistema , Simpatria/fisiologia , Animais , Núcleo Celular/genética , Quirópteros/anatomia & histologia , Ecolocação , Guiana Francesa , Genótipo , Repetições de Microssatélites/genética , Reprodução , Especificidade da EspécieRESUMO
Toothed whales have evolved to live in extremely different habitats and yet they all rely strongly on echolocation for finding and catching prey. Such biosonar-based foraging involves distinct phases of searching for, approaching and capturing prey, where echolocating animals gradually adjust sonar output to actively shape the flow of sensory information. Measuring those outputs in absolute levels requires hydrophone arrays centred on the biosonar beam axis, but this has never been done for wild toothed whales approaching and capturing prey. Rather, field studies make the assumption that toothed whales will adjust their biosonar in the same manner to arrays as they will when approaching prey. To test this assumption, we recorded wild botos (Inia geoffrensis) as they approached and captured dead fish tethered to a hydrophone in front of a star-shaped seven-hydrophone array. We demonstrate that botos gradually decrease interclick intervals and output levels during prey approaches, using stronger adjustment magnitudes than predicted from previous boto array data. Prey interceptions are characterised by high click rates, but although botos buzz during prey capture, they do so at lower click rates than marine toothed whales, resulting in a much more gradual transition from approach phase to buzzing. We also demonstrate for the first time that wild toothed whales broaden biosonar beamwidth when closing in on prey, as is also seen in captive toothed whales and bats, thus resulting in a larger ensonified volume around the prey, probably aiding prey tracking by decreasing the risk of prey evading ensonification.
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Golfinhos/fisiologia , Ecolocação/fisiologia , Comportamento Predatório/fisiologia , Animais , Brasil , Peixes , Rios , Som , Espectrografia do SomRESUMO
The tympanal ear is an evolutionary acquisition which helps moths survive predation from bats. The greater diversity of bats and echolocation strategies in the Neotropics compared with temperate zones would be expected to impose different sensory requirements on the neotropical moths. However, even given some variability among moth assemblages, the frequencies of best hearing of moths from different climate zones studied to date have been roughly the same: between 20 and 60 kHz. We have analyzed the auditory characteristics of tympanate moths from Cuba, a neotropical island with high levels of bat diversity and a high incidence of echolocation frequencies above those commonly at the upper limit of moths' hearing sensitivity. Moths of the superfamilies Noctuoidea, Geometroidea and Pyraloidea were examined. Audiograms were determined by non-invasively measuring distortion-product otoacoustic emissions. We also quantified the frequency spectrum of the echolocation sounds to which this moth community is exposed. The hearing ranges of moths in our study showed best frequencies between 36 and 94 kHz. High sensitivity to frequencies above 50 kHz suggests that the auditory sensitivity of moths is suited to the sounds used by sympatric echolocating bat fauna. Biodiversity characterizes predators and prey in the Neotropics, but the bat-moth acoustic interaction keeps spectrally matched.
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Evolução Biológica , Quirópteros/fisiologia , Ecolocação/fisiologia , Audição/fisiologia , Mariposas/fisiologia , Acústica , Animais , Emissões Otoacústicas Espontâneas , Comportamento PredatórioRESUMO
Toothed whales produce echolocation clicks with source parameters related to body size; however, it may be equally important to consider the influence of habitat, as suggested by studies on echolocating bats. A few toothed whale species have fully adapted to river systems, where sonar operation is likely to result in higher clutter and reverberation levels than those experienced by most toothed whales at sea because of the shallow water and dense vegetation. To test the hypothesis that habitat shapes the evolution of toothed whale biosonar parameters by promoting simpler auditory scenes to interpret in acoustically complex habitats, echolocation clicks of wild Amazon river dolphins were recorded using a vertical seven-hydrophone array. We identified 404 on-axis biosonar clicks having a mean SLpp of 190.3 ± 6.1â dB re. 1â µPa, mean SLEFD of 132.1 ± 6.0â dB re. 1â µPa(2)s, mean Fc of 101.2 ± 10.5â kHz, mean BWRMS of 29.3 ± 4.3â kHz and mean ICI of 35.1 ± 17.9â ms. Piston fit modelling resulted in an estimated half-power beamwidth of 10.2â deg (95% CI: 9.6-10.5â deg) and directivity index of 25.2â dB (95% CI: 24.9-25.7â dB). These results support the hypothesis that river-dwelling toothed whales operate their biosonars at lower amplitude and higher sampling rates than similar-sized marine species without sacrificing high directivity, in order to provide high update rates in acoustically complex habitats and simplify auditory scenes through reduced clutter and reverberation levels. We conclude that habitat, along with body size, is an important evolutionary driver of source parameters in toothed whale biosonars.
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Golfinhos/fisiologia , Ecolocação/fisiologia , Animais , Brasil , Ecossistema , Rios , Som , Espectrografia do SomRESUMO
The sensorimotor approach proposes that perception is constituted by the mastery of lawful sensorimotor regularities or sensorimotor contingencies (SMCs), which depend on specific bodily characteristics and on actions possibilities that the environment enables and constrains. Sensory substitution devices (SSDs) provide the user information about the world typically corresponding to one sensory modality through the stimulation of another modality. We investigate how perception emerges in novice adult participants equipped with vision-to-auditory SSDs while solving a simple geometrical shape recognition task. In particular, we examine the distinction between apparatus-related SMCs (those originating mostly in properties of the perceptual system) and object-related SMCs (those mostly connected with the perceptual task). We study the sensorimotor strategies employed by participants in three experiments with three different SSDs: a minimalist head-mounted SSD, a traditional, also head-mounted SSD (the vOICe) and an enhanced, hand-held echolocation device. Motor activity and fist-person data are registered and analyzed. Results show that participants are able to quickly learn the necessary skills to distinguish geometric shapes. Comparing the sensorimotor strategies utilized with each SSD we identify differential features of the sensorimotor patterns attributable mostly to the device, which account for the emergence of apparatus-based SMCs. These relate to differences in sweeping strategies between SSDs. We identify, also, components related to the emergence of object-related SMCs. These relate mostly to exploratory movements around the border of a shape. The study provides empirical support for SMC theory and discusses considerations about the nature of perception in sensory substitution.