vibration + communication Flashcards
What is the general definition of a vibration?
A periodic motion in an elastic medium where displacement is proportional to force, converting potential energy into kinetic energy in a harmonic motion.
* can be airbourne vibration (sound/acoustic), ground based vibration (seismic), solid or substrate bourne vibration (vibration)
* focus of this lecture is on ground/solid vibration
How does ‘sound’ fit under the umbrella of vibrations?
- Sound is a subset of vibrations specifically traveling through air;
- in this lecture, ‘vibration’ typically refers to those traveling through solid substrates.
What are the main media through which vibrations travel?
Air (sound), water (sonar), and solids/substrates (often just called vibration).
Why is vibration sensing considered a form of mechanosensation?
It involves detecting mechanical oscillations in a medium via specialized receptors (e.g., in ears, legs, etc.).
- it is fast mechanosensation
What is an example of a scenario where both airborne and substrate-borne vibrations are produced?
- Drumming on a surface creates vibrations in the substrate (surface) and acoustic waves in the air simultaneously.
- overlap between sound and vibration signals are multimodal signalling
how does vibration travel through solid?
- intermolecular bonds between atoms allow vibration to travel relative to each other
- solid atomic arrangement allow for fast travel of vibration
overlaps between acoustic and vibration signalling
- when producing vibration signal, often also produces a acoustic signal (multimodal signals)
- some animals can detect both acoustic and vibration signalling using same receptor (or even if using different receptors, it converges to same region of CNS and treated as same type of information)
How do physical constraints influence vibration signals?
- Factors like
1) substrate geometry (shape of branch or surface will vibrate differently)
2) natural frequencies (the resonance properties of materials)
3) material properties (stiffness, density, heterogeneity)
can distort or dampen signals, shaping how animals adapt for detection and generation.
Which organisms commonly use vibration-based communication?
- very broad taxonomic range
- Many invertebrates (insects, arachnids, crustaceans) and
- some vertebrates :
1) elephants - can communicate signals through producing + detecting ground vibrations
2) rabbits (ground stomping)
3) kangaroo rats (foot drumming) AND MANY MORE
What is the difference between signals and cues in vibration communication?
- Signals are evolved specifically for communication (benefiting sender and receiver),
- whereas cues are incidental and can be exploited by others (e.g., predators) - not evolved for communication
How can vibrations be multimodal?
- They often co-occur with other signals (visual, chemical, acoustic),
- and animals may detect them with the same or separate sensory systems
- some animals use same receptors or same CNS region for acoustic + vibration
What are the physical constraints in vibration communication?
1) Substrate geometry affects wave propagation.
2) Material properties (stiffness, density) influence transmission.
3) Natural frequencies can create resonance effects.
4) Wave types (transverse vs. longitudinal) may coexist in one substrate.
Why are vibrations through solids more variable than airborne sound?
- Solids can differ in geometry, density, or moisture, creating an unstable transmission path and requiring specialized adaptations for consistent communication
- might be more difficult to detect (vibration signals become weaker depending on substrate), and unstable
how do animals use to overcome these physical constraints?
- animals can use 4 strategies to over come:
1) adjust vibration input
2) adjust vibration reception sensitivity
3) make own material (spiders spinning silk)
4) move/choose envrionment - they also specialize/modify a combination of behavioura, morphological, and sensory adaptations: such as body structure ans specialised senses
how do animals adjust vibration input?
- they can adjust behavioural and morpholigcal modifications
- they can also adjust the time amplitude and freqauency of vibration input
what are the ways animals can adjust vibration input by behaviour and morphological changes
- vocalization: elephants’ use vocal chords which are loud enough to enter the ground for ground based vibrations for communication
- vibrating body parts: chameleon shaking a branch with legs can transmit vibrations through the branch
- stridulation: Rubbing specialized body parts to produce an acoustic + ground based vibration
- Drumming: fiddler crab: striking substrate w appendase (large claw taps ground)
- buckling tymbals: in cicadas muscular buckle + unbuckle action of tymbals generate koud acoustic vibration + some ground based vibration
how do animals adjust vibration input by adjusting time, frequency and amplitude?
- Time Pattern: How often taps or beats ocur
- Amplitude: Force or intensity of each vibration
- Frequency: Pitch or rate of oscillation (e.g., varying tension in vocal cords).
What is stridulation?
Producing vibrations by rubbing specialized body parts together (e.g., crickets), generating both airborne sound and substrate vibrations.
what is buckling tymbals?
In cicadas, a muscular action “buckles” and “unbuckles” stiff ribs (tymbals) to generate very loud vibrations through air
But some of that also goes into the ground
How can animals adjust vibration input to improve communication?
By modifying the time pattern (rhythm), amplitude (force), and frequency (pitch) of their signals.
how do animals adjust vibration reception sensitivity to enhance detection of vibrations?
- behavioural adjustments: scorpian stance
- morphological adjustments: larger ear ossicles
- sensory adjustments: leg-based sensors
Give an example of a morphological adaptation for vibration reception detection
- Golden moles lack external eyes have enlarged ear ossicles to detect low-frequency ground vibrations
- behaviour to match this morphological adaptation: it often ‘headbutt’ the tunnel floor to enhance detection.
What are some behavioral adaptations for vibration reception detection?
- Scorpion stance: they spread their legs radially to maximize ground contact from all directions ground contact
what are some sensory adaptations for better vibration reception
- insects have leg-based sensors so they can detect ground based vibrations directly through their legs which stand on the ground
- Termites: Primarily detect substrate vibrations over airborne sound through specialized leg receptors.
- Cockroaches: Leg-based receptors can detect both acoustic and substrate vibrations.
- Crickets: Typically prioritize airborne signals (e.g., chirps) with ear structures, though some leg-based sensors also exist.
- the location and function of receptors are adapted to what signals they prioritize/encounter most
What is the overarching importance of vibration communication for animals?
- It allows a wide range of species to send and receive critical information (mating, territory, predator/prey cues), even in complex or dark environments.
- allows faster communication via solid than acoustic
Summarize the core differences between vibration and sound.
Vibration is the broader term for periodic motion in any medium; sound specifically refers to vibrations traveling through air, often perceived by auditory organs.
Why might some animals create or choose their environment to improve vibration transmission?
Selecting or modifying a substrate with favorable properties (e.g., spider silk tension) ensures more reliable or stronger signal propagation.
What are the key takeaways from these notes?
(1) Vibrations vs. sound distinctions,
(2) Physical constraints of substrate-borne signals,
(3) Widespread biological conserved across taxa,
(4) Adaptations in signal generation and sensory reception to cope with environmental challenges.
how do spiders overcome physical constraints of vibration
- they make their own material - silk
- this prevents unstable vibration transmission due to substrate geometry and material
- ensure stable signal of vibration as they determine the silk properties, hence determining vibration signal strength
Why are silk vibrations important for orb-weaver spiders?
- Orb-weaver spiders rely on vibrations in their web to confirm prey contact and triggers predatory response
- airborne sounds (buzzing of a fly) alone usually do not trigger a predatory response.
What is morphological computing in the context of spider webs?
- It refers to the web itself performing part of the ‘information processing,’
- the web acts as an extended phenotype to process vibratory information to information on prey location without having to use CNS of spider
- offloads on the central nervous system because the web itself process vibratory signals
What are the spider sensory structures?
- Trichobothria (specialized hairs) detect airborne vibrations (not primary focus today)
- Slit sensilla on exoskeleton detect substrate-borne vibrations in the web, transmitting information about prey impacts.
- slits in exoskeleton spanned by membranes attached with sensory cells which fire impulses when membrane deformed which is caused by web vibrations
How do orb-weaver spiders typically position themselves on the web?
- They hang head-down with legs radiating around the hub,
- this stance maximizing contact with multiple radial threads for better vibratory detection from each direction of the web
What is active sensing (‘bouncing’) in spiders?
- Spiders deliberately bounce on their web to vibrate their web (like an echolocation pulse)
- to detect if prey is present and refine location information when prey stops struggling (when prey no longer generated vibration, the re-vibrate the web to locate prey)
Why do orb-weaver spiders have extremely high vibration sensitivity?
- They can detect nanometer-scale displacements (around 1000 Hz),
- can detect even very small vibrations in web
- which aligns with the typical frequencies produced by struggling insects in the web.
How do spiders differentiate between prey and non-prey vibrations?
- They use frequency and temporal patterns (e.g., insect buzzing vs. leaf movement) to decide whether to attack;
- they make decisions quickly in milliseconds
what does the web act as for spiders
- act as information processor
- extended phenotype for morphological computation
How do spiders locate prey in the web?
- Direction: Determined by comparing which leg experiences the strongest vibration amplitude. which radial thread has biggest amplitude
- Distance: use direction cues first, but distance possibly via triangulation using amplitude ratios. Triangulation is amplitude ratios of transverse waves across legs
What do spiders do if prey stops struggling?
They may bounce the web to re-generate vibrations (like echolocation), or sometimes use olfactory cues if the prey remains motionless.
How is morphological computing in spiders relevant to robotics research?
Understanding how the web ‘offloads’ computation can inspire designs for robots that rely on external structures to process sensory information.
Key Takeaways - Spider Vibration Communication
- Web vibrations confirm prey presence.
- Morphological computing reduces neural load.
- Sensory structures (slit sensilla) detect substrate vibrations.
- Active “bouncing” helps locate prey when it stops moving.
- Frequency and amplitude cues guide the spider’s response.
how do elephants communicate using vibration
- they communicate alarm cues through seismic signals
- seismic = ground vibrations
What are elephant rumbles, and why are they significant?
- They are low-frequency, high-amplitude vocalizations that travel both through air and the ground, enabling elephants to communicate over long distances via seismic waves.
how do elephants adjust input vibrations
- elephant rumbles
- footfall vibrations
How do footfalls create seismic vibrations?
- amplitude of footfall vibration depends on:
- body mass,
- gait (walking vs. running), and
- foot morphology (padded foot vs. hoof), elephant have padded foot so doesn’t actually create signal to noise ratio, but still can communicate through this
What are the elephant vibration detection mechanisms using morphology? How do elephants use morphological adaptations to detect vibrations
- Impedance matching mechanism
- via fatty foot pads, fatty footpads minimize vibration kinetic energy loss, ensuring enough energy conducted from ground to leg bone
- Bone conduction through leg bones to the middle ear, elephants are sensitive to bone conduction
- enlarged ear ossicles (more sensitive detection of low freq vibrations)
- Pacinian corpuscles in the feet sensitive to low-frequency signals (maches freq of rumbles)
- elephant cochlea have narrow bandwidtch and sensitive to small frequency changes
What is impedance matching in elephants’ feet?
- A dense fatty cushion in their feet reduces vibration energy loss, ensuring seismic signals travel efficiently from the ground through the leg bones to the ear.
How do Pacinian corpuscles help elephants detect vibrations?
- These specialized receptors in the dermis of the foot are tuned to low-frequency signals, matching the rumble frequencies elephants produce.
how do elephants use behaviour to enhance vibration reception
- Freezing
- Leaning forward stance
- orientation
Why do elephants sometimes freeze upon detecting seismic vibrations?
- By standing still, they minimize self-generated noise, allowing more precise detection and interpretation of ground-based vibrations
why do elephants have a leaning forward stance when detecting vibrations
- more weight on forefeet
- to improve contact with substrate
How do elephants use body orientation to improve seismic reception?
- They often align perpendicular to the incoming wavefront of vibration,
- enhancing the difference in signals received by each foot to pinpoint the source’s direction.
What are the playback experiments and responses in elephants?
- Rodwell 2006
- Alarm rumbles played seismically cause defensive grouping and vigilance (group defense and vigilance)
- Elephants orient toward the signal source
- They avoid areas where alarm vibrations were transmitted
What did Rodwell’s experiments reveal about elephants distinguishing callers?
- Rodwell 2007
- Elephants can differentiate between familiar and unfamiliar alarm rumbles, reacting more strongly to vibrations from known individuals.
How does anthropogenic (human-made) noise affect elephants?
- Seismic playback of human anthropogenic white noise superimposed on alarm rumbles causes stronger avoidance,
- elephants retreat further when increasing noise
- indicating that human-generated vibrations can disrupt elephant behaviours
What are some benefits of seismic detection for elephants?
- The slower velocity of ground waves compared to airborne sound can help elephants localize signals more accurately
- by comparing the vibrations arriving at each foot.
What is applied conservation research related to elephants?
- Large arrays of ground-based sensors can detect wildlife vibrations
- seismic rumbles can locate elephants, and are sometimes more accurate than acoustic methods
- Machine learning techniques to identify elephant rumbles and vibrations
- Helps prevent human-elephant conflict by providing early warnings
How do researchers link seismic data to specific wildlife events?
They combine seismic recordings with camera trap images, matching vibration patterns to known species behaviors (e.g., elephants walking, rumbling).
What future conservation applications do seismic sensors offer?
Automated alerts for elephants near farmland, integration with camera traps and GPS, and rapid response systems to reduce human–wildlife conflict.
What are the combined lecture insights?
- vibration prone to physical contraints
- animals use Behavioral, morphological, and sensory adaptations overcome substrate constraints
- Spiders use webs as ‘extended phenotypes’ for vibration processing
- Elephants rely on seismic rumbles for communication over large ranges
- Seismic monitoring aids conservation by detecting and tracking animals in real time
Why are vibrations through materials a crucial source of information for animals?
- They provide reliable signals in diverse environments, though subject to physical constraints that animals overcome through specialized adaptations.
How do spiders and elephants illustrate the range of vibration communication strategies?
- Spiders generate their own substrate (silk) and rely on slit sensilla,
- while elephants use bone conduction, foot pads, and seismic rumbles for long-distance communication.
What makes vibration-based monitoring valuable for conservation?
- It allows remote, real-time detection of animal movements and behaviors, enabling interventions to protect wildlife and reduce conflict with humans.
