Preliminary analysis of echolocation signals produced by fleeing Irrawaddy dolphins(Orcaella brevirostris)

In this study, echolocation signals were recorded from a wild Irrawaddy dolphin(Orcaella brevirostris) in shallow water in the Bay of Brunei. During sound recording, a small fishing boat engine startled a nearby Irrawaddy dolphin and began chasing it on two occasions. Variations in the acoustic parameters were detected. When the Irrawaddy dolphin was startled and chased, the sound pressure level, number of click trains per minute, pulse number, and average inter-pulse interval(PI) per click train were all affected. The PI increased and exhibited a slight downward trend during the chase. The increase in PI indicated an increase in the inspection distance as the dolphin escaped. Thus, Irrawaddy dolphins may adapt their echolocation signals to stand out from ambient noise in the wild and to improve their search efforts in potentially risky situations. Appropriate management of the burst noise around the dolphins is important.

Design and Benchmark Tests of a Multi-Channel Hydrophone Array System for Dolphin Echolocation Recordings

This paper describes in depth the design and application considerations of a computer based measurement system enabling 1 MS/s simultaneous sampling of 47 hydrophones for cross sectional recordings of echolocation beams of toothed whales (Odontocetes). An earlier prototype version of the system has previously only been presented as a brief proof of principle that did not offer a complete description of the software and hardware solution. Crucial hardware and software design considerations of the further developed system include the re-arm times of the burst mode sampling and the dual-core distributed execution of the software components. The rearm time was measured to 283 μs, using a 550 μs long sample window around each click. This enables burst mode sampling of clicks with an inter-click interval as short as 833 μs. It is shown through both synthetic benchmark tests of the system and through field measurements of bottlenose dolphins (Tursiops truncatus) and a beluga whale (Delphinapterus leucas) that it is capable of acquiring, analyzing and visualizing data in run-time. It operates effectively also in highly reverberant surroundings like concrete pools and shallow waters. Burst mode sampling allows the system to block reflections with 0.3 - 0.5 m longer propagation paths than the direct path. It is suggested that the system’s compliance to reverberant recording sites makes it valuable in future dolphin echolocation studies.

An Analysis of Foraging and Echolocation Behavior of Swarm Intelligence Algorithms in Optimization: ACO, BCO and BA

Optimization techniques are stimulated by Swarm Intelligence wherever the target is to get a decent competency of a problem. The knowledge of the behavior of animals or insects has a variety of models in Swarm Intelligence. Swarm Intelligence has become a potential technique for evolving many robust optimization problems. Researchers have developed various algorithms by modeling the behaviors of the different swarm of animals or insects. This paper explores three existing meta-heuristic methods named as Ant Colony Optimization (ACO), Bee Colony Optimization (BCO) and Bat Algorithm (BA). Ant Colony Optimization was stimulated by the nature of ants. Bee Colony Optimization was inspired by the plundering behavior of honey bees. Bat Algorithm was emerged on the echolocation characteristics of micro bats. This study analyzes the problem-solving behavior of groups of relatively simple agents wherein local interactions among agents, are either directly or indirectly through the environment. The scope of this paper is to explore the characteristics of swarm intelligence as well as its advantages, limitations and application areas, and subsequently, to explore the behavior of ants, bees and micro bats along with its most popular variants. Furthermore, the behavioral comparison of these three techniques has been analyzed and tried to point out which technique is better for optimization among them in Swarm Intelligence. From this, the paper can help to understand the most appropriate technique for optimization according to their behavior.

Adaptive temporal patterns of echolocation and flight behaviors used to fly through varied-sized windows by 2 species of high duty cycle bats

As actively sensing animals guided by acoustic information, echolocating bats must adapt their vocal–motor behavior to various environmentsand behavioral tasks. Here, we investigated how the temporal patterns of echolocation and flight behavior were adjusted in 2 species of batswith a high duty cycle (HDC) call structure, Rhinolophus ferrumequinum and Hipposideros armiger, when they flew along a straight corridorand then passed through windows of 3 different sizes. We also tested whether divergence existed in the adaptations of the 2 species. Both H.armiger and R. ferrumequinum increased their call rates by shortening the pulse duration and inter-pulse interval for more rapid spatial samplingof the environment when flying through smaller windows. Bats produced more sonar sound groups (SSGs) while maintaining a stable proportion of calls that made up SSGs during approaches to smaller windows. The 2 species showed divergent adjustment in flight behavior across3 different window sizes. Hipposideros armiger reduced its flight speed to pass through smaller windows while R. ferrumequinum increasedits flight speed. Our results suggest that these 2 species of HDC bats adopt similar acoustic timing patterns for different tasks although theyperformed different flight behaviors.

Morphology of crater and caldera lakes in the Far Eastern region of Russia and the features of their development

Volcanic lakes in the Kuril-Kamchatka region are difficult to access,and for this reason,they remain poorly studied,with only scattered and brief data available.The authors have conducted a study of 10 lake basins using modern digital echolocation survey techniques and have also compiled and summarized published data for 15 lakes in the region,calculating their main morphometric characteristics.It has been established that many caldera lake basins are modified by young explosive funnels,extrusive or effusive domes,and exhibit traces of hydrothermal activity.While lakes of the same genetic type in the Kuril-Kamchatka region are similar in depth and depression forms,the group of caldera lakes shows less homogeneity across all morphometric indicators.It was found that the absolute heights of the reservoirs on Kamchatka Peninsula are generally greater than those on the Kuril Islands,as is often the case with the size of their basins.The volcanic lakes under study can rapidly change their volume and shape under the influence of endogenous processes.For the first time for this region,on the base of repeated observations,underwater extrusive dome rate growth and the approximate rates of 2 lake level changes were calculated.Repeated observations of lakes in the Ksudach calderas(Kamchatka)and on Simushir Island indicate approximate rates of level changes:a decrease ranging within 0.5-0.6 m per year(over a 27-year observation interval)and an increase reaching up to 0.26 m per year(over a 48-year interval).The growth rate of the underwater extrusive dome in Lake Shtyubel has averaged 1-1.6 m per year over the past 25 years.This analysis has facilitated the first generalization regarding the morphology and developmental features of crater and caldera lakes in the Kuril-Kamchatka region of Russia,representing an important step in their study.The results obtained will provide a solid foundation for subsequent research in this region and may be of interest to researchers studying other volcanic lakes.

Echolocation calls of Myotis frater (Chiroptera: Hipposi- deridae) during search flight

Echolocation calls of Myotis frater emitted during the search phase consist of brief frequency-modulated pulses. The sound signals are comprised of three harmonics of which the first one is of the highest intensity and occurs in all echolocation calls. The frequency of this fundamental harmonic ranges from 110.8 to 50.2 kHz, and its duration is about 3.5 ms. The second and the third harmonics are relatively weak, occurring in 50.0% and 25.0% of echolocation calls respectively, with frequencies ranging from 138.4 to 116.6 kHz for the second harmonic and from 193.6 to 170.8 kHz for the third harmonic. We presume that, according to the echolocation call features, Myotis frater probably forages the insects on the ground of complex environments.

Patterns and causes of geographic variation in bat echolocation pulses

Evolutionary biologists have a long-standing interest in how acoustic signals in animals vary geographically,because divergent ecology and sensory perception play an important role in speciation.Geographic comparisons are valuable in determining the factors that influence divergence of acoustic signals.Bats are social mammals and they depend mainly on echolocation pulses to locate prey,to navigate and to communicate.Mounting evidence shows that geographic variation of bat echolocation pulses is common,with a mean 5-10 kHz differences in peak frequency,and a high level of individual variation may be nested in this geographical variation.However,understanding the geographic variation of echolocation pulses in bats is very difficult,because of differences in sample and statistical analysis techniques as well as the variety of factors shaping the vocal geographic evolution.Geographic differences in echolocation pulses of bats generally lack latitudinal,longitudinal and elevational patterns,and little is known about vocal dialects.Evidence is accumulating to support the fact that geographic variation in echolocation pulses of bats may be caused by genetic drift,cultural drift,ecological selection,sexual selection and social selection.Future studies could relate geographic differences in echolocation pulses to social adaptation,vocal learning strategies and patterns of dispersal.In addition,new statistical techniques and acoustic playback experiments may help to illustrate the causes and consequences of the geographic evolution of echolocation pulse in bats.

Relationship between echolocation frequency and body size in two species of hipposiderid bats

Frequencies of echolocation calls with maximum power of Himalayan leaf-nosed bats and Horsfield’s leaf-nosed bats during searching phase were 74.1 and 92.1 kHz, respectively. Head-body length, forearm length and body mass of Himalayan leaf-nosed bats were 82.9 mm, 89.7 mm and 59.1 g, respectively; and the corresponding values of Horsfield’s leaf-nosed bats were 68.4 mm, 61.3 mm and 19.7 g, respectively. Echolocation frequency and the three parameters of body size, head-body length, forearm length and body mass, were all negatively correlated, and the correlation coefficients were -0.86, -1.58 and -2.19, respectively. This study thereby proved that echolocation frequency and body size were negatively correlated in the two species of hipposiderid bats.

A blind climber:The first evidence of ultrasonic echolocation in arboreal mammals

The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(translated as“the blind mouse”)is incapable of object vision:the retina is folded and retains no more than 2500 ganglion cells in the focal plane,and the optic nerve is subject to gliosis.Hence,Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation.Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis.The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession.Structurally,these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species,but they are too faint to be revealed with a common bat detector.When recording video simultaneously with the ultrasonic audio,a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated.Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the“echolocation-first theory”of pre-flight origin of echolocation in bats.

Functional correlates of skull shape in Chiroptera:feeding and echolocation adaptations

Morphological,functional,and behavioral adaptations of bats are among the most diverse within mammals.A strong association between bat skull morphology and feeding behavior has been suggested previously.However,morphological variation related to other drivers of adaptation,in particular echolocation,remains understudied.We assessed variation in skull morphology with respect to ecology(diet and emission type)and function(bite force,masticatory muscles and echolocation characteristics)using geometric morphometrics and comparative methods.Our study suggests that variation in skull shape of 10 bat families is the result of adaptations to broad dietary categories and sound emission types(oral or nasal).Skull shape correlates with echolocation parameters only in a subsample of insectivorous species,possibly because they(almost)entirely rely on this sensory system for locating and capturing prey.Insectivores emitting low frequencies are characterized by a ventrally tilted rostrum,a trait not associated with feeding parameters.This result questions the validity of a trade-off between feeding and echolocation function.Our study advances understanding of the relationship between skull morphology and specific features of echolocation and suggests that evolutionary constraints due to echolocation may differ between different groups within the Chiroptera.

Identification of sympatric bat species by the echolocation calls

One hundred and thirty-eight echolocation calls of 63 free-flying individuals of five bat species(Rhinolophus ferrumequinum,Myotis formosus,Myotis ikonnikovi,Myotis daubentoni and Murina leucogaster)were recorded(by ultrasonic bat detector(D980))in Zhi’an village of Jilin Province,China.According to the frequency-time spectra,these calls were categorized into two types:FM/CF(constant frequency)/FM(R.ferrumequinum)and FM(frequency modulated)(M.formosus,M.ikonnikovi,M.daubentoni and M.leucogaster).Sonograms of the calls of R.ferrumequinum could easily be distinguished from those of the other four species.For the calls of the remaining four species,six echolocation call parameters,including starting frequency,ending frequency,peak frequency duration,longest inter-pulse interval and shortest inter-pulse interval,were examined by stepwise discriminant analysis.The results show that 84.1%of calls were correctly classified,which indicates that these parameters of echolocation calls play an important role in identifying bat species.These parameters can be used to test the accuracy of general predictions based on bats’morphology in the same forest and can provide essential information for assessing patterns of bat habitat use.

Neuroplasticity, limbic neuroblastosis and neuro-regenerative disorders

The brain is a dynamic organ of the biological renaissance due to the existence of neuroplasticity. Adult neurogenesis abides by every aspect of neuroplasticity in the intact brain and contributes to neural regeneration in response to brain diseases and injury. The occurrence of adult neurogenesis has unequivocally been witnessed in human subjects, experimental and wildlife research including rodents, bats and cetaceans. Adult neurogenesis is a complex cellular process, in which generation of neuroblasts namely, neuroblastosis appears to be an integral process that occur in the limbic system and basal ganglia in addition to the canonical neurogenic niches. Neuroblastosis can be regulated by various factors and contributes to different functions of the brain. The characteristics and fate of neuroblasts have been found to be different among mammals regardless of their cognitive functions. Recently, regulation of neuroblastosis has been proposed for the sensorimotor interface and regenerative neuroplasticity of the adult brain. Hence, the understanding of adult neurogenesis at the functional level of neuroblasts requires a great scientific attention. Therefore, this mini-review provides a glimpse into the conceptual development of neuroplasticity, discusses the possible role of different types of neuroblasts and signifies neuroregenerative failure as a potential cause of dementia.

The role of ultrasonic bat detectors in improving inventory and monitoring surveys in Vietnamese karst bat assemblages

Bats account for 30% of mammal diversity in SE Asia and are potential bioindicators of wider biodiversity impacts resulting from habitat loss and climate change. As existing sampling techniques in the region typically fail to record bats that habitually fly in open areas and at higher altitudes, current inventory efforts are less than comprehensive. Acoustic sampling with bat detectors may help to overcome these limitations for insectivorous bats, but has yet to be tested in mainland SE Asia. To do so, we sampled bats while simultaneously recording the echolocation calls of insectivorous species commuting and foraging in a variety of karst habitats in north Vietnam. Monitoring of cave-dwelling bats was also undertaken. Discriminant function analysis of 367 echolocation calls produced by 30 insectivorous species showed that acoustic identification was feasible by correctly classifying 89. 1% of calls. In all habitats, acoustic sampling and capture methods recorded significantly more species each night than capture methods alone. Capture methods consequently failed to record 29% （ten spp. of aerial insectivores） of the bat fauna in commuting and foraging habitats and 11% （two spp. ） of that in our cave sample. Only four of these species were subsequently captured following significantly greater sampling effort. This strongly suggests that acoustic methods are indispensable for maximizing bat inventory completeness in SE Asia. As accurate inventories and monitoring are essential for effective species conservation, we recommend the inclusion of acoustic sampling in future studies of bat assemblages across the region [ Current Zoology 55 （5） ： 327 - 341, 2009].

Research of New Concept Sonar—Cognitive Sonar

The performance of a sonar system is closely related to the marine environment and the target characteristics. When dealing with the echoes of a traditional active sonar system, the sonar designers often do not take into account the influence of the environmental information and prior knowledge perceived by sonar receivers, making it difficult to obtain desired processing results. Based on the basic principle and key technology of sonar, this paper proposed a cognition-based intelligent sonar system in theory--cognitive sonar. Cognitive sonar is capable of jointly optimizing the transmission waveform and receiver according to the changes of environment so that its detection and identification performance can be significantly improved.

Cannot see you but can hear you: vocal identity recognition in microbats

Identity recognition is one of the most critical social behaviours in a variety of animal species. Microchiropteran bats present a special use case of acoustic communication in the dark. These bats use echolocation pulses for navigating, foraging, and communicating; however, increasing evidence suggests that echolocation pulses also serve as a means of social communication. Compared with echolocation signals, communication calls in bats have rather complex structures and differ substantially by social context. Bat acoustic signals vary broadly in spectrotemporal space among individuals, sexes, colonies and species. This type of information can be gathered from families of vocalizations based on voice characteristics. In this review we summarize the current studies regarding vocal identity recognition in microbats. We also provide recommendations and directions for further work.

Convergences in the diversification of bats

Twenty-five characters or suites of characters from bats are considered in light of changes in bat classification. Thecharacters include some associated with flower-visiting (two), echolocation (12), roosting (six), reproduction (two) and three areof unknown adaptive function. In both the 1998 and 2006 classifications of bats into suborders (Megachiroptera and Microchiropteraversus Yinpterochiroptera and Yangochiroptera, respectively), some convergences between suborders are the same (e.g.,foliage roosting, tent building), but others associated with echolocation differ substantially. In the 1998 phylogeny convergencesassociated with echolocation (high duty cycle echolocation, nasal emission of echolocation calls) occurred among the Microchiroptera.In the 2006 phylogeny, they occur between Yinpterochiroptera and Yangochiroptera. While some traits apparently aroseindependently in two suborders (e.g., foliage-roosting, tent building, low intensity echolocation calls, noseleafs, nasal emission ofecholocation calls, high duty cycle echolocation behaviour), others appear to have been ancestral (roosting in narrow spaces,laryngeal echolocation, stylohyal-tympanic contact, oral emission of echolocation calls, and small litter size). A narrow profilethrough the chest is typical of bats reflecting the thoracic skeleton. This feature suggests that the ancestors of bats spent the day insmall crevices. Features associated with laryngeal echolocation appear to be ancestral, suggesting that echolocation evolved earlyin bats but was subsequently lost in one yinpterochiropteran lineage .

Potential impacts of shipping noise on Indo-Pacific humpback dolphins and implications for regulation and mitigation:a review

Shipping noise is a widespread and relatively loud sound source among human-induced underwater sounds.The impacts of shipping noise are of special concern for Indo-Pacific humpback dolphins(Sousa chinensis),as they inhabit shallow and nearshore habitats and are highly dependent on sound for survival.This study synthesizes our current understanding of the potential impacts of shipping noise on Indo-Pacific humpback dolphins combined with knowledge on sound production and hearing of these animals and the impacts of noise on other whales and dolphins.For further protection and management of Indo-Pacific humpback dolphins and their habitats,shipping noise should be regulated and mitigated to modify sound from ships,to reduce overall noise levels,and to set more marine protected areas(MPAs)covering most Indo-Pacific humpback dolphin habitats with seasonal and geographical restrictions to avoid ensonification of shipping noise.The emphasis for future research should be on obtaining more baseline information about the population distribution,sound production,hearing capabilities at the population level,behavior,and stress hormones of the humpback dolphins under different noise conditions or under different noise-producing activities,and/or in high-noise areas compared with relatively quiet areas,and the noise characteristics of ships of different types,sizes and speeds.

Cochlear hair cells of echolocating bats are immune to intense noise

Exposure to intense noise can damage cochlear hair cells,leading to hearing loss in mammals.To avoid this constraint,most mammals have evolved in relatively quiet environments.Echolocating bats,however,are naturally exposed to continuous intense sounds from their own and neighboring sonar emissions for maintaining sonar directionality and range.Here,we propose the presence of intense noise resistance in cochlear hair cells of echolocating bats against noise-induced hearing loss(NIHL).To test this hypothesis,we performed noise exposure experiments for laboratory mice,one nonecholocating bat species,and five echolocating bat species.Contrary to nonecholocating fruit bats and mice,the hearing and the cochlear hair cells of echolocating bats remained unimpaired after continuous intense noise exposure.The comparative analyses of cochleae transcriptomic data showed that several genes protecting cochlear hair cells from intense sounds were overexpressed in echolocating bats.Particularly,the experimental examinations revealed that ISL1 overexpression significantly improved the survival of cochlear hair cells.Our findings support the existence of protective effects in cochlear hair cells of echolocating bats against intense noises,which provides new insight into understanding the relationship between cochlear hair cells and intense noises,and preventing or ameliorating NIHL in mammals.

The adaptive value of increasing pulse repetition rate during hunting by echolocating bats

During hunting, bats of suborder Microchiropetra emit intense ultrasonic pulses and analyze the weak returning echoes with their highly developed auditory system to extract the information about insects or obstacles. These bats progressively shorten the duration, lower the frequency, decrease the intensity and increase the repetition rate of emitted pulses as they search, approach, and finally intercept insects or negotiate obstacles. This dynamic variation in multiple parameters of emitted pulses predicts that analysis of an echo parameter by the bat would be inevitably affected by other co-varying echo parameters. The progressive increase in the pulse repetition rate throughout the entire course of hunting would presumably enable the bat to extract maximal information from the increasing number of echoes about the rapid changes in the target or obstacle position for successful hunting. However, the increase in pulse repetition rate may make it difficult to produce intense short pulse at high repetition rate at the end of long-held breath. The increase in pulse repetition rate may also make it difficult to produce high frequency pulse due to the inability of the bat laryngeal muscles to reach its full extent of each contraction and relaxation cycle at a high repetition rate. In addition, the increase in pulse repetition rate increases the minimum threshold （i.e. decrease auditory sensitivity） and the response latency of auditory neurons. In spite of these seemingly physiological disadvantages in pulse emission and auditory sensitivity, these bats do progressively increase pulse repetition rate throughout a target approaching sequence. Then, what is the adaptive value of increasing pulse repetition rate during echolocation？ What are the underlying mechanisms for obtaining maximal information about the target features during increasing pulse repetition rate？ This article reviews the electrophysiological studies of the effect of pulse repetition rate on multiple- parametric selectivity of neurons in the central nucleus of the inferior colliculus of the big brown bat, Eptesicusfuscus using single repetitive sound pulses and temporally patterned trains of sound pulses. These studies show that increasing pulse repetition rate improves multiple-parametric selectivity of inferior collicular neurons. Conceivably, this improvement of multiple-parametric selectivity of collicular neurons with increasing pulse repetition rate may serve as the underlying mechanisms for obtaining maximal information about the prey features for successful hunting by bats.

Characteristics of echolocating bats’auditory stereocilia length, compared with other mammals

The stereocilia of the Organ of Corti in 4 different echolocating bats, Myotis adversus, Murina leuco-gaster, Nyctalus plancyi (Nyctalus velutinus), and Rhinolophus ferrumequinum were observed by using scanning electron microscopy (SEM). Stereocilia lengths were estimated for comparison with those of non-echolocating mammals. The specialized lengths of outer hair cells (OHC) stereocilia in echolocating bats were shorter than those of non-echolocating mammals. The specialized lengths of inner hair cells (IHC) stereocilia were longer than those of outer hair cells stereocilia in the Organ of Corti of echolocating bats. These characteristics of the auditory stereocilia length of echolocating bats represent the fine architecture of the electromotility process, helping to adapt to high frequency sound and echolocation.