Biology subjects

Umadi, R.

Publications and source records attributed to Umadi, R..

10 recordsLinked to original sources

bioRxiv2026

RUBAT Studio: A Unified Workbench for Multichannel Bioacoustic Data Acquisition

AO_SCPLOWBSTRACTC_SCPLOWO_LIHigh-resolution ultrasonic recording is central to modern bioacoustics, behavioural ecology, and passive acoustic monitoring. Yet, implementing flexible, multichannel acquisition systems with real-time playback, monitoring and experimental control remains technically demanding. Existing solutions often require bespoke code development or expensive proprietary systems, limiting experimental accessibility and reproducibility. C_LIO_LII present RUBAT Studio (v4.0), an integrated software platform for multichannel ultrasonic recording, real-time heterodyne monitoring for experimental control and data acquisition in laboratory and field environments. The system supports high sample rates, configurable channel routing, automated triggering, retrospective ring-buffer capture, calibration-aware visualisation, and modular signal-processing integration. Its architecture is designed for extensibility, enabling synchronised acquisition across multiple microphones and compatibility with custom hardware configurations. C_LIO_LIField and laboratory testing with devices ranging from USB microphones to analogue microphones via professional audio interfaces confirmed stable multichannel acquisition at sampling rates up to 384 kHz over multi-hour sessions without crashes or artefacts. Real-time heterodyne monitoring, dual-channel live spectrograms, and calibrated sound-pressure-level display provided immediate acoustic and visual feedback throughout data collection. The platform enables complex experimental paradigms, including spatial localisation studies, closed-loop playback experiments, active-sensing investigations, and array-based behavioural assays, without requiring specialised knowledge of audio systems. C_LIO_LIBy lowering the technical barrier to high-performance audio recording and experimental control, RUBAT Studio expands the methodological toolkit available to behavioural ecologists and bioacousticians. The platform facilitates rigorous, scalable and reproducible acoustic research designs, enabling experiments that were previously technically prohibitive and thereby advancing the study of animal communication, spatial hearing and active sensing. C_LI

ecology↗

bioRxiv2026

WAH-i: Optimising Microphone Array Geometry for Customised Localisation Accuracy

Accurate spatial localisation of free-flying echolocating bats is foundational for resolving fine-scale flight and echolocation behaviour, prey interception, and spatial decision-making in natural environments. Acoustic localisation using microphone arrays is widely employed for this purpose, yet array geometries in field studies are typically chosen heuristically rather than systematically optimised. As portable multichannel ultrasonic recording systems become increasingly accessible, principled design guidelines are needed to ensure reliable localisation performance under practical deployment requirements. I introduce an iterative array optimisation algorithm that designs microphone geometries by maximising localisation reliability within a predefined three-dimensional field of interest. The method evaluates candidate geometries using simulated acoustic emissions and time-difference-of-arrival localisation, quantifying performance as a volumetric pass rate: the proportion of source locations that meet a user-defined accuracy threshold. Microphone positions are iteratively perturbed and accepted based on improvements to this task-level metric, while enforcing practical constraints on array aperture, inter-sensor spacing, and deployability. Across canonical polyhedral geometries, random initialisations, and arrays comprising four to twelve microphones, optimisation consistently produced rapid early gains followed by geometry-dependent performance plateaus under the specified stopping criterion and iteration budget. Under fixed-aperture constraints, increasing the microphone count yielded diminishing returns, and optimised low-order arrays-particularly four-microphone configurations-matched or exceeded the volumetric localisation performance of higher-order arrays with suboptimal geometry. Analysis of optimisation trajectories further revealed that convergence dynamics scale with array order, whereas volumetric performance under the tested conditions is dominated by geometry rather than sensor number. These results demonstrate that array geometry is the primary determinant of volumetric localisation reliability, and that efficient, portable arrays can be systematically designed using optimisation rather than heuristic rules. The proposed framework is broadly applicable to bioacoustic localisation problems beyond echolocating bats, including avian tracking, passive acoustic monitoring, and conservation-oriented sensing, and provides a general approach for designing task-optimised acoustic sensor arrays for a wide range of applications.

animal behavior and cognition↗

bioRxiv2026

Rates, Ripples, and Responsivity: The Geometry of Echolocation in Water-Foraging Bats

Water-surface foraging is a rare strategy among echolocating bats, requiring precise coordination between sonar emission, echo timing, and flight geometry. Here, I develop a geometric-responsivity framework to explain how bats foraging over water regulate call timing under these constraints. The model links beam projection, flight height, and specular surface reflections to predictable call-rate scaling and near-field interference patterns. Field recordings of Myotis daubentonii reveal spatially invariant spectral ripples across microphones, confirming a geometric interference origin rather than receiver-dependent effects. Reanalysis of classic data from Noctilio leporinus shows that call rates are inconsistent with continuous prey-distance locking and instead reflect regulation relative to stable surface-related echoes, with prey-centred control emerging only at close range. Together, these results demonstrate that water-foraging bats structure call timing using environmental reference echoes, providing a mechanistic explanation for the acoustic constraints that shape this specialised foraging niche.

animal behavior and cognition↗

bioRxiv2025

ESPERDYNE: A Dual-Band Heterodyne Monitor and Ultrasound Recorder for Bioacoustic Field Surveys

1. BackgroundUltrasonic monitoring is essential for ecological studies of bats and other animals, yet high-performance field devices remain prohibitively expensive and inaccessible-particularly in biodiversity-rich regions with limited research infrastructure. Existing low-cost options often lack real-time listening and recording features. There remains a critical need for versatile, affordable, and field-ready tools that support acoustic behavioural research, educational and conservation outreach. 2. New ToolI introduce Esperdyne, an open-source, dual-channel ultrasound monitoring and recording system based on the ESP32-S3 microcontroller. With a component cost under {euro}75, Esperdyne combines real-time heterodyne monitoring, stereo recording from a retroactive ring buffer, and an intuitive rotary-based user interface with OLED display. It supports full-duplex 192 kHz audio, dual-band tuning for simultaneous FM/CF monitoring, and real-time playback via headphones or a speaker. All audio processing-including adjustable carrier frequency mixing, gain control, and file-saving logic-is implemented without reliance on fixed-rate audio libraries. 3. ApplicationsEsperdyne has been tested in field conditions and shown to reliably detect high-SNR calls and harmonics from free-flying bats. A companion tool Bat Reviewer supports rapid inspection, playback, and export of selected recordings. Together, these tools enable portable, solo-operated acoustic surveys with minimal training. Beyond ecological research, Esperdyne is suitable for education, outreach, and preliminary field assessments in remote or resource-constrained settings. Its modular design encourages hardware customisation and firmware extension by interdisciplinary teams. 4. Availability and ImplementationFull hardware schematics, firmware, and software tools are publicly available. The system can be built using hobbyist-accessible components and standard Arduino tooling. By sharing this system openly, I aim to lower technical barriers and foster broader participation in ultrasound-based biodiversitymonitoring and conservation. Esperdyne demonstrates how microcontroller-based platforms can bridge gaps between affordability, usability, and scientific capability-supporting global efforts in soundscape ecology.

animal behavior and cognition↗

bioRxiv2025

Embedded Ultrasonics: A Microcontroller-Based Multichannel Ultrasound Recorder for Behavioural Field Studies

Background: A variety of behavioural studies of echolocation and acoustic communication in free-flying bats depend on multichannel ultrasonic recordings. However, access to these methods remains geographically uneven: tropical and subtropical regions harbour much of the world's bat diversity yet remain underrepresented in experimental behavioural bioacoustics. Conventional systems often depend on costly audio interfaces, laptops, and specialist expertise. Although instrumentation is only one contributor to this disparity, a compact, affordable, openly documented platform can reduce a practical barrier to field research, ecological monitoring, and conservation efforts. Results: Here, I present BATSY4-PRO, an open-source four-channel recorder designed for behavioural and ecological field studies. Built around a Teensy 4.1 microcontroller and two WM8782 analogue-to-digital converters, it records synchronised 16-bit audio at 192 kHz directly to microSD storage. The recorder weighs under 150 g, operates from a 5 V supply, and, together with the four-microphone array, can be constructed for approximately 200 euros. It combines retrospective and buffer-prefilled forward recording with selectable real-time monitoring. While all four full-spectrum channels are recorded, users can monitor any individual microphone or a four-channel mix through tunable heterodyne conversion or direct passthrough. Field recordings showed consistently high signal-to-noise ratios comparable to recordings obtained with a commercially available multichannel soundcard and supported time-difference-of-arrival localisation of bat flight trajectories. Because the intended applications involve moving animals, I used grid-based Monte Carlo simulations to define the usable localisation field of the deployed array and evaluate how simulated source velocity affects localisation performance. The simulations identified a geometry-dependent near-array region of useful performance, followed by a sharp decline in accuracy with increasing range, and showed that localisation errors increased with simulated source velocity. Conclusions: BATSY4-PRO establishes an open, reproducible workflow from synchronised field recording and real-time monitoring to three-dimensional source localisation. Its configurable firmware logic and extensibility allow the same compact system to be adapted to distinct behavioural questions, species, and habitats without dependence on laboratory-bound or proprietary multichannel platforms. Wider adoption can expand the geographic and taxonomic scope of experimental bat bioacoustics, strengthen local capacity for ecological monitoring, and enable comparative investigation of echolocation behaviour under natural conditions.

animal behavior and cognition↗

bioRxiv2025

Swarm Cohesion in Bats Emerges from Stable Temporal Loops

O_LICohesive animal groups rely on continuous behavioural updating to regulate spacing, alignment, and collision avoidance, yet all sensory-guided interaction is constrained by finite signal propagation delays, processing time, and motor latency. In actively sensing species such as echolocating bats, these constraints raise a fundamental ecological question: what limits the stability and density of cohesive groups under increasing interaction load? C_LIO_LII develop a constraint-based framework in which neighbour-based interaction is treated as a closed-loop process that is only feasible when sensory updates can be acquired, processed, and acted upon within a finite temporal budget. Building on an asynchronous swarm simulation grounded in echo-timed biosonar control, I formalise two receiver-side feasibility constraints that become critical in dense groups: (i) temporal overlap between conspecific calls and the echo-processing window, and (ii) level dominance of the tracked neighbours echo over competing conspecific signals. C_LIO_LIBoth constraints emerge as probabilistic feasibility boundaries rather than binary conditions for perceptual success or failure. Across a broad parameter space of responsivity, group density, and flight speed, the fraction of call events supporting reliable neighbour-based updates declines smoothly with compounded interaction load. Temporal overlap is organised by a single compound term integrating local density, neighbourhood call rate, call duration, and echo delay, while level dominance operates in a marginal regime where masking is frequent but intermittent. C_LIO_LISimulation results show that stable, collision-averse swarm cohesion can persist across wide ranges of density and motion without explicit coordination or interference avoidance, provided that sufficiently frequent informative updates remain available. Breakdown occurs not because echoes become undetectable, but because the probability of obtaining timely, behaviourally relevant updates falls below what is required to sustain closed-loop control. C_LIO_LITogether, these findings identify temporal feasibility and interaction dominance as general constraints shaping cohesion, spacing, and fragmentation in actively sensing animal groups. Rather than invoking acoustic jamming as a failure mode, the framework reframes interference as a background condition that regulates the statistics of actionable information. This closed-loop perspective provides a unifying ecological principle for collective behaviour in active sensing systems and generates testable predictions for when cohesion should persist or fail under increasing sensory and interactional demand. C_LI

animal behavior and cognition↗

bioRxiv2025

Temporal Precision Necessitates Wingbeat-Call Asynchrony in Actively Echolocating Bats

Echolocating bats operate within a closed sensorimotor loop in which call emission, echo reception, sensory processing, and motor response are linked by finite propagation delays and bounded response times. Although synchrony between wingbeats and call timing is frequently observed, it remains unclear when such coordination is temporally feasible and when it must necessarily break down. Here, I develop a constraint-based framework formalising how temporal feasibility limits shape wingbeat-call coordination during active echolocation. Building on the responsivity framework, the analysis derives explicit conditions under which call emission remains phase-locked to a cyclic motor rhythm, and identifies regimes in which phase locking becomes progressively infeasible as acoustic delay shrinks and call rate rises during prey approach. Simulations across three motor-control configurations - fixed wingbeat frequency and excursion, dynamically adjusted frequency, and dynamically adjusted frequency and excursion - show that transitions from synchrony to asynchrony arise as necessary consequences of delayed feedback and bounded motor dynamics, rather than discrete changes in behavioural strategy. Increasing motor flexibility extends the synchrony-permissive range of call rates but does not eliminate the feasibility boundary. Simulation ensembles spanning biologically plausible parameter combinations confirm that regime transitions are robust and that asynchronous call phases exhibit structured clustering near the feasibility boundary. Empirical observations of transient decoupling during prey pursuit and the terminal buzz are consistent with these predicted transitions. The results identify temporal feasibility as a governing constraint on echolocation behaviour, clarify how apparent closed-loop coordination can arise without tight motor coupling, and generate testable predictions for when and why wingbeat-call synchrony must fail during prey capture.

animal behavior and cognition↗

bioRxiv2025

Biosonar Responsivity Sets the Stage for the Terminal Buzz

The temporal patterning of bat echolocation has been extensively characterised and used to interpret behavioural regulation during active foraging. Yet a general mathematical account linking these patterns to acoustic propagation, relative motion, and the timing of behaviourally selected information remains incomplete. Here we present the responsivity framework, which represents each call event as a delayed active-sensing cycle composed of an acoustic acquisition interval and a subsequent behavioural interval. Their proportional relation is described by the responsivity coefficient, kr, connecting call timing to effective anchor distance, relative velocity, call duration, and the selected echo window. We evaluate the framework through analytical derivation, call-by-call simulation, internal validation, and comparison with field recordings from free-flying bats. The framework generates the characteristic hyperbolic relation between call rate and anchor distance, explains how echo-window selection shifts approach timing, and places the terminal buzz at the near-target limit of the same timing process rather than requiring a separate buzz-specific rule. Responsivity and kinematics had separable terminal effects: kr strongly constrained terminal update density and the attainable call rate, whereas closing velocity determined the time available within the terminal region and hence potential buzz duration. The framework also identified a buzz-readiness state preceding complete buzz expression, while transient sonar strobe groups emerged under multi-target anchor allocation without an explicit grouping rule. Application to field recordings showed broad correspondence between empirical and simulated movement-timing and call-duration organisation, and illustrated how the framework can be used to evaluate latent acquisition-window and anchor assumptions against observed timing. Together, these results support responsivity as a process-based descriptor of echolocation timing and highlight its potential as a diagnostic and analytical framework for hypothesis generation and empirical testing.

animal behavior and cognition↗

bioRxiv2025

Oscillating Ears Dynamically Transform Echoes in Constant-Frequency Bats

Constant-frequency (CF) bats exhibit rapid oscillations of their external ears. Yet, the functional role of these movements has remained unresolved since their initial documentation over half a century ago. Although recent studies have demonstrated that pinna motion generates Doppler shifts, they do not explain why ear oscillations intensify at close range or how these dynamics contribute to echo perception. In this study, I investigate the hypothesis that oscillatory ear movements enhance echo information during CF echolocation. Using a simplified receiver-motion model, I examine how time-varying pinna pose reshapes the temporal and spectral structure of returning echoes. I show that ear oscillations inject dynamic transformations into the received signal, producing multiple informative views of the same echo and increasing both temporal contrast and spectral diversity around the CF carrier. These transformations are strongest under behavioural conditions in which target-state uncertainty is expected to be high, offering a potential functional explanation for the long-standing observation that ear-oscillation rate increases as bats approach a target. The results suggest that oscillatory ear movements act as an adaptive, receiver-side mechanism that enhances echo information during CF echolocation, complementing the well-known emitter-side adaptations of high-duty-cycle biosonar.

animal behavior and cognition↗

bioRxiv2025

Widefield Acoustics Heuristic: Advancing Microphone Array Design for Accurate Spatial Tracking of Echolocating Bats

Accurate three-dimensional localisation of ultrasonic bat calls is essential for advancing behavioural and ecological research. I present a comprehensive, open-source simulation framework--Array WAH --for designing, evaluating, and optimising microphone arrays tailored to bioacoustic tracking. The tool incorporates biologically realistic signal generation, frequency-dependent propagation, and advanced Time Difference of Arrival (TDoA) localisation algorithms, enabling precise quantification of both positional and angular accuracy. The framework supports both frequency-modulated (FM) and constant-frequency (CF) call types, the latter characteristic of Hipposiderid and Rhinolophid bats, which are particularly prone to localisation errors due to their long-duration emissions. A key innovation is the integration of source motion modelling during call emission, which introduces Doppler-based time warping and phase shifts across microphones--an important and often overlooked source of error in source localisation. I systematically compare four array geometries--a planar square, a pyramid, a tetrahedron, and an octahedron--across a volumetric spatial grid. The tetrahedral and octahedral configurations demonstrate superior localisation robustness, while planar arrays exhibit limited angular resolution. My simulations reveal that spatial resolution is fundamentally constrained by array geometry and the signal structure, with typical localisation error ranging between 5-10 cm at 0.5 m arm lengths. By providing a flexible, extensible, and user-friendly simulation environment, Array WAH supports task-specific design and deployment of compact, field-deployable localisation systems. It is especially valuable for investigating the acoustic behaviour of free-flying bats under naturalistic conditions, and complements emerging low-power multichannel ultrasonic recorders for field deployment and method validation.

animal behavior and cognition↗