A hidden target creates a difficult information problem.
The operator cannot act accurately because the target cannot yet be seen, measured or located. However, obtaining more information may itself carry a cost.
An active probe can illuminate the environment, but it may also reveal the operator, alert the target, create interference or alter the behaviour being observed.
Passive observation avoids sending such a signal. Yet it depends on the target or environment producing enough usable information on its own.
This creates a recurring strategic decision:
Should a system generate the signal it needs, or should it remain quiet and extract information from signals already present?
Echolocating bats and barn owls illuminate these two architectures particularly well.
An echolocating bat sends energy into its environment and analyses the returning echoes. It creates an information event, controls its timing and repeatedly updates its estimate of the target.
A barn owl does not normally illuminate prey with an equivalent acoustic probe. It listens for sounds produced by the prey, separates minute differences in their arrival at its two ears, turns towards the source and approaches while minimising the noise generated by its own flight.
The first architecture creates information.
The second architecture waits for, filters and exploits information.
Neither is universally superior. Each controls a different part of the detection problem.
The Strategic Question
When a target is hidden, should a system:
- actively probe the environment to manufacture the information it lacks;
- passively listen for signals generated by the target;
- or switch between both architectures as uncertainty, exposure and time pressure change?
The operator may be a predator searching for prey, a teacher diagnosing an unseen misconception, an engineer locating a fault, an institution detecting emerging failure or an AI system deciding whether to request additional information.
The objective is not merely detection.
The objective is to obtain sufficiently reliable information before the opportunity disappears, while controlling:
- exposure;
- interference;
- energy and attention costs;
- false positives;
- target adaptation;
- and the risk of acting on an incomplete estimate.
The central contrast is therefore not simply sound versus silence.
It is who carries the burden of producing the information event.
Executive Thesis
The echolocating-bat architecture takes the initiative in sensing.
The operator emits a controlled probe, receives the return, compares successive measurements and adjusts the next probe according to the remaining uncertainty. This architecture is powerful when the target is quiet, time is limited and the operator can probe without unacceptable exposure or interference.
The barn-owl architecture transfers the signal-generation burden to the target.
The operator suppresses its own noise, positions sensitive receivers, waits for target-generated emissions and extracts location from very small differences inside the incoming signal. This architecture is powerful when the target already produces distinctive information and active probing would reveal the observer, disturb the target or corrupt the natural behaviour being measured.
The deeper StrategizeOS mechanism is:
Signal-Initiative Allocation — the decision to place control of information production with the searching operator, the target, or a managed sequence between the two.
This mechanism produces a second law:
Active sensing increases control over information availability but may increase exposure and environmental disturbance. Passive sensing reduces probe exposure but sacrifices control over when sufficient information will appear.
The valid strategy depends on the relationship between information scarcity and information cost.
Why These Cases Matter
The comparison is useful because bats and barn owls operate under a broadly similar problem:
- low-light or dark environments;
- small or partially hidden prey;
- limited time before escape;
- noisy natural surroundings;
- and a requirement to convert uncertain sensory evidence into a physical interception.
Their sensory architectures, however, place information control in different locations.
For the bat, a major part of the information stream begins with the bat’s own emission.
For the barn owl, the decisive acoustic stream begins primarily with the prey or surrounding environment.
The StrategizeOS Article Production Protocol requires the comparison to remain bounded rather than turning the source cases into decorative archetypes. The protocol distinguishes the public explanation from the underlying evidence dossier and requires the article to move from strategic problem to verified observations, mechanism, rival explanations, conditional rule, transfer and limits.
Comparison boundary
Source cases
This article examines echolocating insectivorous bats, with particular support from research on species such as the big brown bat and other aerial or gleaning bats, against the barn owl, commonly studied under the name Tyto alba.
Unit of analysis
The unit is the individual predator’s hidden-target detection architecture.
Environment
The main boundary is nocturnal or visually restricted hunting in which acoustic information contributes substantially to locating prey.
In scope
- control of signal production;
- information update rate;
- receiver sensitivity;
- exposure created by sensing;
- environmental interference;
- target counterdetection;
- and switching between active and passive acquisition.
Out of scope
This is not a complete comparison of bat and owl intelligence, ecology, morality, evolutionary success or total hunting ability.
It does not claim that every bat hunts in the same way or that barn owls rely exclusively on hearing.
The comparison concerns a controlled strategic variable:
How should a system acquire information about a target that cannot yet be directly observed?
What the Evidence Shows
The echolocating bat: manufacturing an acoustic return
Active sensing occurs when an organism or system releases energy into the environment and analyses how the environment modifies or returns that energy. Echolocation is a major biological example because the bat generates the outgoing acoustic signal used to probe its surroundings.
The bat is therefore not limited to waiting for an insect to make a useful sound.
It can emit a pulse, receive the echo and use the return to estimate properties such as direction, distance and movement. The time between emission and return contains range information, while changes across successive echoes support tracking and interception.
This creates a controllable sensing cycle:
Emit → receive → compare → update → emit again.
The bat can alter aspects of this cycle as the task changes.
Research on active echolocation shows that bats adjust call timing, pulse repetition, direction and other signal properties as they search for, approach and intercept targets. The interval between pulses generally decreases as the bat nears a target, culminating in the rapid sequence commonly called a terminal buzz.
This means the sensing system does not merely collect more of the same data.
It changes the structure and rate of information acquisition according to the stage of the hunt.
During broad search, the bat must inspect a larger acoustic space.
During approach, it must refine the target estimate.
During interception, it needs rapid updates because both predator and prey may be moving quickly.
Bats can also actively control their acoustic field of view and orient their heads and ears in ways that improve three-dimensional localization. Experiments with big brown bats show that action and sensor positioning contribute to the quality of the spatial cues received.
Echolocating bats do not rely only on the most recent return. Research on tracking moving targets indicates that bats can accumulate information across successive acoustic observations and form predictive estimates of target movement, including during brief occlusion.
The bat architecture therefore provides more than detection.
It provides an operator-controlled stream of repeated measurements capable of supporting prediction.
The cost of taking the sensing initiative
Active sensing does not produce free information.
The signal must be generated, transmitted and separated from returning echoes and competing sounds. In acoustically crowded conditions, calls from other bats or deliberately interfering signals may reduce the clarity of the return. Bats may alter their calls, change position or even cease vocalising briefly when continued emission becomes counterproductive.
The outgoing signal may also be detected by the target.
Many moths possess hearing systems capable of detecting bat ultrasound. Some respond by steering away, diving or performing evasive manoeuvres. Others produce ultrasonic counter-signals that may warn, startle, deflect or interfere with an attacking bat.
The active probe can therefore change the behaviour being measured.
Once the target detects the search signal, the original detection problem becomes an interactive contest.
The bat is no longer merely locating the prey.
It may be locating prey that now knows it is being located.
This creates detection–exposure coupling:
The act that improves the operator’s information may simultaneously improve the target’s information about the operator.
Some bats reduce this cost through quieter calls or by combining echolocation with passive listening. Research on gleaning bats shows that certain species listen for prey-generated rustling, mating calls or wing sounds, while using weaker echolocation for orientation or supplementary information. Other bats alternate between aerial hawking and passive gleaning according to prey and habitat conditions.
The evidence therefore prevents an excessive archetype.
The bat is not permanently active.
It can shift the sensing initiative when active emission becomes too revealing, too noisy or less profitable.
The barn owl: extracting position from target-generated sound
Barn owls can locate and capture prey under extremely poor illumination and have demonstrated the ability to orient towards sound sources in darkness. Their auditory systems use differences in the arrival time and level of sound at the two ears to derive spatial direction.
The barn owl’s facial ruff and asymmetrical external ear structures shape incoming sound before it reaches the auditory system.
Interaural time differences contribute strongly to horizontal localization, while interaural level differences and frequency-dependent cues contribute to vertical localization. Experimental simulation of facial-ruff removal produced substantial impairment, particularly in elevation judgement and in resolving some ambiguous source positions.
The owl’s architecture begins from a different position than echolocation.
The owl does not normally need to create a loud outgoing acoustic pulse and wait for its reflection from the prey.
Instead, it uses sounds already produced by:
- the prey’s movement;
- contact with vegetation or ground;
- vocalisation;
- or other disturbances associated with the target.
The basic sequence becomes:
Suppress self-noise → receive target signal → compare binaural differences → orient → approach → update from further target sound.
The information event is initiated mainly by the target.
The owl’s strategic investment is therefore placed in receiver quality, spatial processing, orientation and self-noise control.
Silent movement as information preservation
Quiet flight is often described only as stealth.
Stealth may indeed reduce the warning available to prey. However, another important explanation is that reduced wing noise prevents the owl’s own movement from masking the faint sounds it needs to hear. Reviews of owl flight identify both prey-concealment and self-masking reduction as plausible functions, with the relative contribution dependent on ecological conditions.
This matters strategically.
A passive receiver does not remain effective merely by refusing to transmit.
It must also protect the incoming signal from its own operational noise.
For a barn owl, sensing quality depends partly on keeping movement from contaminating the channel through which the target is being located.
The architecture is therefore not:
Do nothing and listen.
It is:
Shape the receiver, reduce self-generated interference, position carefully and allow the target’s own activity to reveal its location.
This may be called Receiver-Dominant Detection.
The system spends capability on extracting more information from a weak existing signal rather than generating a stronger new signal.
The cost of transferring initiative to the target
Passive listening avoids some of the exposure created by active probing.
However, it loses direct control over information timing.
A quiet target can create a severe detection gap.
Background noise, wind, competing sound sources, reverberation or an acoustically confusing surface may reduce the signal-to-noise ratio. The owl may receive too little information, ambiguous information or information from the wrong source.
Passive architecture therefore contains a waiting cost.
The operator may need to:
- remain in position;
- move to improve geometry;
- wait for another target emission;
- integrate several sounds;
- or use another sensory channel.
Barn owls are not purely auditory machines. Research indicates that they commonly combine visual and auditory information, while visual experience also contributes to the calibration and development of accurate auditory spatial maps.
Nor is passive listening behaviourally inactive.
The owl turns its head towards a source and may reposition to improve the estimate. Its receivers are passive in the sense that they do not require an echolocation-like outgoing probe, but the animal still actively controls orientation and movement.
This distinction is essential:
Passive signal acquisition can still require active sensor positioning.
The Central Strategic Contrast
| Strategic dimension | Echolocating-bat architecture | Barn-owl architecture |
|---|---|---|
| Information origin | Operator-generated probe and returning echo | Target- or environment-generated sound |
| Sensing initiative | Primarily held by the searcher | Primarily transferred to the target |
| Control of sampling time | High | Limited by target emissions |
| Information update rate | Adjustable through pulse timing | Dependent on incoming signal frequency |
| Primary investment | Transmitter, receiver and rapid probe–return processing | Receiver sensitivity, directional filtering and self-noise reduction |
| Strength against quiet targets | Potentially high if they return detectable echoes | Weak if they produce no usable sound |
| Exposure risk | Probe may reveal the searcher or alter target behaviour | Lower acoustic-probe exposure |
| Interference risk | Echo clutter, jamming and competing calls | Background masking, ambiguity and weak target emissions |
| Adaptation | Change pulse rate, beam, frequency, route or sensing mode | Change orientation, position, waiting time or sensory channel |
| Dominant advantage | Control over information production | Low-disturbance extraction of naturally produced information |
| Main failure | Probe becomes costly, revealing or corrupted | Necessary information never appears |
| Recovery route | Reduce emission, reposition, change waveform or switch to passive cues | Reposition, wait, integrate more cues or introduce a controlled probe |
The table describes two different allocations of information control.
The bat concentrates capability around signal generation and rapid updating.
The owl concentrates capability around signal preservation and extraction.
The Mechanism Beneath the Comparison
The surface comparison is simple:
The bat sends sound.
The owl listens.
The strategic mechanism is deeper.
Signal-Initiative Allocation
A hidden-target detection system must decide who will initiate the information event.
There are three possible allocations.
1. Operator-initiated information
The operator releases a probe and observes the response.
This is the bat-like architecture.
Its general sequence is:
Hidden target
→ controlled probe
→ environmental return
→ target estimate
→ adjusted probe
→ reduced uncertainty
→ commitment.
Its main operational variable is:
How much usable information does each probe create relative to its cost and exposure?
When probe yield is high, the operator gains control over the sensing tempo.
When probe yield is low, the operator may only create noise, warning or false confidence.
2. Target-initiated information
The operator waits for the target to emit, move or otherwise reveal itself.
This is the barn-owl-like architecture.
Its sequence is:
Hidden target
→ target-generated emission
→ sensitive reception
→ signal separation
→ spatial estimate
→ quiet approach
→ commitment.
Its main operational variable is:
How reliably does the target generate a distinctive signal before the opportunity closes?
When target emission is reliable, the operator can remain difficult to detect while allowing the target to disclose its own position.
When target emission is sparse or ambiguous, the operator may wait without convergence.
3. Sequentially shared initiative
The operator begins with passive acquisition, introduces a narrow probe only when uncertainty remains too high, and then returns to passive observation to verify the result.
Alternatively, the operator may begin with a broad active scan, switch to reduced emission during approach and rely increasingly on passive or accumulated information near commitment.
This hybrid is a StrategizeOS synthesis derived from the comparison. It is not presented as a separate biological species category.
Its sequence is:
Passive watch
→ anomaly or partial signal
→ targeted active probe
→ refined estimate
→ reduced-emission verification
→ action or withdrawal.
The purpose of the hybrid is not to average two strategies.
It is to assign each architecture to the stage where its benefits exceed its costs.
A Second Mechanism: Detection–Exposure Coupling
Active and passive sensing differ in how information acquisition changes the information state of other actors.
An active probe may produce two returns:
- information returned to the operator;
- information leaked to the target.
The active architecture succeeds only when the first return is more valuable than the second.
A passive receiver may avoid this leakage, but it faces a different coupling:
- the operator remains concealed;
- the operator becomes dependent on the target’s willingness or need to emit.
The passive architecture succeeds only when concealment is more valuable than control over sampling time.
This produces the governing trade-off:
Active sensing purchases information with exposure.
Passive sensing purchases concealment with waiting and uncertainty.
The costs are not always equal, and they are not always monetary or energetic.
They may appear as:
- target adaptation;
- behavioural disturbance;
- system disruption;
- privacy intrusion;
- delayed decisions;
- missed opportunities;
- or confidence built on an incomplete signal.
What Else Could Explain the Result?
The comparison must survive several rival explanations.
Rival explanation 1: the difference is merely anatomical
The bat has a biosonar system. The barn owl has specialised directional hearing.
Anatomy clearly matters. However, anatomy does not eliminate the strategic mechanism. It demonstrates that each system has invested resources in a different location within the information chain.
The bat invests heavily in generating and interpreting returns.
The owl invests heavily in receiving, filtering and localising external signals.
The transferable lesson is not to copy an animal organ. It is to identify where a designed system should place sensing capability.
Rival explanation 2: one architecture is simply more advanced
The evidence does not justify this conclusion.
Active echolocation can detect targets that produce little useful sound, but it can encounter clutter, jamming and counterdetection.
Passive listening may preserve concealment and natural target behaviour, but it can fail when the target is quiet or the environment is noisy.
Each architecture solves a different information problem.
Rival explanation 3: bats are active and owls are passive
This is too rigid.
Some bats use passive prey sounds, combine sensory channels or stop vocalising in difficult acoustic conditions. Barn owls actively orient their heads, alter position and combine hearing with vision.
The permitted conclusion is that the two cases provide strong examples of different dominant architectures.
The impermissible conclusion is that every bat always uses active echolocation while every barn owl always relies exclusively on passive hearing.
Rival explanation 4: silence alone explains the owl’s success
Quiet flight may reduce detection by prey, reduce self-masking or serve both functions. Current evidence supports the importance of low-noise flight but does not justify reducing the entire owl architecture to stealth alone.
The owl’s advantage also depends on receiver geometry, auditory processing, target sound and usable approach conditions.
Rival explanation 5: more information is always better
Information can be expensive, misleading or behaviour-changing.
A high-rate active sensor may collect large quantities of corrupted echoes.
A highly sensitive passive receiver may collect large quantities of irrelevant noise.
The objective is not maximum signal volume.
It is sufficient decision-relevant information with controlled distortion.
The Conditional Decision Rule
Use the echolocating-bat architecture when:
- the target is unlikely to produce reliable signals;
- the environment can return a useful response to a probe;
- the operator needs control over sampling time;
- the target may move before passive evidence accumulates;
- repeated updates materially improve interception;
- probe exposure is tolerable;
- and the operator can distinguish returns from clutter and interference.
The architecture is especially suitable when remaining passive would leave the system nearly blind.
Use the barn-owl architecture when:
- the target already emits distinctive information;
- active probing would alert, disturb or alter the target;
- preserving natural behaviour is important;
- the operator can invest in receiver sensitivity and signal separation;
- environmental noise remains manageable;
- and the decision window allows waiting, repositioning or repeated listening.
The architecture is especially suitable when the target can be induced to reveal itself simply by being allowed to continue operating.
Use a hybrid when:
- passive observation can narrow the search area but not resolve the target;
- active probing is useful only after uncertainty has been reduced;
- broad probes would create excessive exposure;
- the system can lower probe intensity as it approaches commitment;
- or passive verification is needed after an active test.
The hybrid should not run both modes continuously without purpose.
It should define a switch condition.
A useful switch rule is:
Remain passive while naturally occurring information is reducing uncertainty at an acceptable rate. Introduce the smallest effective probe when passive uncertainty stops falling faster than the decision window closes.
Do not use either architecture when:
- the signal cannot be separated from noise;
- the consequences of a false detection are unacceptable;
- the target cannot be ethically or legally monitored;
- the probe could cause disproportionate harm;
- or the operator has no repair or withdrawal route after an incorrect estimate.
In such conditions, the correct action may be to delay commitment, redesign the sensor architecture or obtain authorised human review.
When the Active-Echolocation Strategy Works
The bat-like architecture is valid when the environment is sufficiently responsive to probing.
It requires:
- a probe capable of reaching the relevant space;
- a return that contains target-specific information;
- timing and processing fast enough for the target’s movement;
- protection against self-interference;
- and a manageable relationship between detection range and exposure.
It becomes dominant when information scarcity is the primary constraint.
Success signals include:
- each probe materially reducing the possible target area;
- stable tracking across successive returns;
- lower uncertainty as the update rate rises;
- correct prediction of target movement;
- and convergence without disproportionate counterreaction.
When the Passive-Listening Strategy Works
The owl-like architecture is valid when useful emissions already exist.
It requires:
- a target that makes detectable sound;
- sufficient receiver sensitivity;
- directional separation;
- low self-generated noise;
- a manageable ambient acoustic environment;
- and enough time to integrate the evidence.
It becomes dominant when probe exposure is more dangerous than information delay.
Success signals include:
- repeated target emissions producing consistent location estimates;
- improved confidence without changing target behaviour;
- continued concealment during approach;
- and convergence through receiver positioning rather than stronger transmission.
When the Strategies Fail
Active-sensing failure
The bat-like architecture becomes weak when:
- the outgoing probe reveals the operator too early;
- the target changes behaviour after detecting the probe;
- multiple operators produce mutual interference;
- clutter creates misleading returns;
- the probe does not reach or reflect from the target;
- or the operator mistakes increased data volume for increased certainty.
Warning signals include:
- estimates becoming less stable as probing increases;
- stronger target evasion after each probe;
- rising interference;
- repeated reacquisition of the same uncertainty;
- and greater sensing expenditure without improved decisions.
The repair route is to reduce transmission, change position, alter the probe, narrow the search field, use another sensory channel or switch temporarily to passive acquisition.
The abort condition is reached when further probing improves the target’s defensive position faster than it improves the operator’s estimate.
Passive-sensing failure
The owl-like architecture becomes weak when:
- the target stops emitting;
- the target signal is not distinctive;
- background noise masks the source;
- several sources produce similar cues;
- the receiver geometry is poor;
- or the decision window closes before enough evidence appears.
Warning signals include:
- long observation without narrowing uncertainty;
- inconsistent directional estimates;
- repeated orientation towards false sources;
- rising dependence on assumptions;
- and delayed action without improved confidence.
The repair route is to reposition, wait for a better signal corridor, integrate another sensory channel or introduce a limited active test.
The abort condition is reached when remaining passive has become indistinguishable from operating without information.
Transfer into Education: Detecting the Hidden Misconception
A student’s visible wrong answer is often the final output of an earlier hidden error.
The unseen target may be:
- a misunderstood definition;
- a false assumption;
- a missing prerequisite;
- an incorrect procedure;
- weak retrieval;
- or a correct idea applied under the wrong condition.
The teacher faces the same architectural decision.
Should the misconception be actively elicited through direct questions and designed tasks, or passively inferred from the student’s natural work?
The bat-like diagnostic lesson
The teacher actively creates an information event.
A carefully selected question, variation, counterexample or request for explanation is sent into the student’s knowledge system.
The response is the return.
The teacher then adjusts the next question according to what the answer reveals.
The sequence is:
Diagnostic question
→ student response
→ error interpretation
→ narrower question
→ revised explanation
→ transfer check.
This is useful when the student cannot spontaneously explain the problem or when passive observation has not revealed the precise failure.
However, excessive questioning may alert the student to the answer being tested. It can also create performance anxiety or cause the learner to imitate cues rather than reveal genuine understanding.
The owl-like diagnostic lesson
The teacher initially remains quiet and observes:
- where the student pauses;
- which line is erased;
- what is attempted first;
- which information is ignored;
- how the student explains the work to a peer;
- and whether the same error appears without prompting.
The misconception is detected from naturally produced learning signals.
This preserves the original structure of the student’s thinking.
However, passive observation may fail when the student hides uncertainty, copies procedures or produces too little work to reveal the underlying model.
The educational hybrid
A strong diagnostic sequence is:
Observe natural work
→ identify the likely error corridor
→ introduce one targeted question
→ repair the misconception
→ return to unprompted work
→ verify independent transfer.
This hybrid is a StrategizeOS synthesis.
The passive stage protects the authenticity of the evidence.
The active stage reduces the remaining uncertainty.
The final passive stage checks whether learning survives after the teacher’s probe has been removed.
The educational decision rule is:
Do not test everything immediately. First observe what the learner reveals naturally. Probe only where the remaining uncertainty prevents accurate teaching.
Limits, Safety and Ethics
Predatory behaviour provides a source case for sensing architecture. It does not provide a moral model for human relationships.
The transferable mechanism is information acquisition under uncertainty.
The literal predation, concealment and target exploitation must not be transferred into education, governance or organisational management.
In human systems:
- passive listening must not become unauthorised surveillance;
- active probing must not become harassment or entrapment;
- students must not be humiliated to expose weaknesses;
- employees must not be manipulated merely to test loyalty;
- personal data should be minimised;
- and high-consequence decisions must remain reviewable.
Passive sensing is not automatically ethical because it is quiet.
Observation can be more intrusive than an openly declared test.
Active sensing is not automatically unethical because it changes the environment.
A transparent, consented diagnostic may be safer than covert monitoring.
The ethical question is therefore separate from the architectural question:
A system must determine not only whether a probe will work, but whether it has the right to send it or to listen for the resulting information.
Human judgement remains necessary where dignity, privacy, consent, safety or irreversible consequences are involved.
Strategic Summary
Source lesson
The echolocating bat commonly takes control of information production by sending adjustable acoustic probes and analysing their returns.
The barn owl commonly takes control of information extraction by receiving target-generated sounds through a specialised directional auditory system while reducing self-generated noise.
Mechanism lesson
The central mechanism is Signal-Initiative Allocation.
A hidden-target detection system may place the burden of producing information with:
- the operator;
- the target;
- or a deliberate sequence between both.
Decision lesson
Use active sensing when the target is quiet and the operator must manufacture information.
Use passive sensing when the target already emits useful signals and active probing would create excessive exposure, disturbance or distortion.
Use a staged hybrid when naturally occurring evidence can narrow the search but cannot safely complete it.
Boundary lesson
The comparison does not prove that bats are purely active or barn owls purely passive.
Both cases contain variation, multimodal sensing and active movement.
The strategic distinction concerns the dominant origin of the information used to reduce uncertainty.
The final law is:
When information is absent, create a return.
When information is already escaping from the target, improve the receiver.
When both costs matter, remain passive broadly and probe narrowly.
Compact Research Basis
- The StrategizeOS Article Production Protocol v3.0 establishes the required problem-first sequence, comparison boundary, evidence discipline, mechanism extraction, rival testing, conditional rules, transfer limits and public-article hard stop.
- Research on active sensing defines the architecture as the use of self-generated energy to probe an environment and documents the adaptive control of sonar signals by echolocating bats.
- Studies of big brown bats and other echolocating species show adaptive pulse timing, active control of acoustic field of view, head and ear orientation, target tracking and predictive accumulation of successive acoustic observations.
- Research on bat–insect interactions and acoustic interference documents the exposure, counterdetection and jamming costs that can accompany active echolocation.
- Studies of gleaning bats demonstrate that bats may also exploit prey-generated sound, use weak echolocation or switch between active and passive foraging modes.
- Barn-owl research documents sound-source localisation through binaural timing and level cues, the contribution of facial-ruff geometry and ear asymmetry, and the importance of orientation, visual calibration and multimodal integration.
- Research on owl flight supports low-noise flight as part of the hunting architecture while retaining both prey-stealth and self-masking reduction as relevant explanations rather than collapsing the result into a single unqualified claim.