Sensory Ecology Flashcards
What is sensory ecology?
The study of how organisms acquire and respond to information
What two types of questions does sensory ecology deal with?
Mechanistic questions
Functional questions
What are the 8 sensory systems?
Vision Olfaction Audition Taste Mechanoreception Thermoreception Magnetoreception Electroreception
Why is it bluer the deeper into the ocean you go?
Red and green wavelengths are absorbed more and UV light is scattered more
What is the average depth of the ocean? After what depth is there no light from sunlight?
4000 metres
After 1000 metres
What is the primary sense for the majority of animals?
Sight
What is the issue with artificial light?
It is a global anthropogenic pollutant and a major threat to the natural world
What does anthropogenic mean?
Originating in human activity
What is light?
An electromagnetic wave, but in sight only the electric field is important, not the magnetic part
What is the equation for wavelength?
Wavelength = speed / frequency
What are the properties of speed, frequency and wavelength to remember?
Speed - always constant in a vacuum
Frequency - always constant and tells us about energy
Wavelength - colour
What wavelengths are what colour?
<400mn - ultraviolet 400-500nm - blue 500-600nm - green 600-700nm - red >700nm - near infrared
What is the structure of the eyes of the Robber fly and what genus is it in?
Genus Holocephala
Eyes highly sensitive with high acuity - they capture prey with a constant bearing angle strategy
What type of eye do most animals have?
Compound eyes
What type of eye do many vertebrates have?
Camera eye
How is an image formed in the human eye?
The focusing is done by the cornea and lens together. An image is formed on the retina at the back of the eye
Why is vision blurry in water?
Water has a lower refractive power so there is a smaller difference in refractive power between the cornea and the water. Images focused far behind the retina
What two types of photoreceptor cell do vertebrates possess?
Rods and cones
What do cones provide to vision?
Colour sensitivity
What are the three types of cones?
Short wavelength - blue sensitive
Mid wavelength - green sensitive
Long wavelength - red sensitive
What animals have four types of cones and what are they known as? What is the extra cone type?
Many fish and birds, they are known as tetrachromats
The extra cone is ultraviolet sensitive
How does light stimulate rods and cones?
Light moves through the eye, through the cell bodies rods and cones to the visual pigments at the more distant end of the rods and cones.
What eyes does a nautilus have?
Pin hole camera eyes - they possess adjustable pupil that dilates or constricts in response to sudden changes in light intensity. Gives them relatively high resolution considering they have no lens, although the image will always be quite dark as there is only a limited area for light to enter the eye
What feature do deep-sea sharks possess and what is its benefit?
They have a reflecting mirror called a tapetum st the back of their eye. The mirror is made from
How many types of invertebrate eye are there? How many of those are compound eyes?
10
8 are compound eyes
What are superposition eyes?
An invertebrate eye which forms a single erect image
Light from different angles goes to different photoreceptors
What are apposition eyes?
Eyes that form multiple inverted images
All light from one facet goes to the same photoreceptor cells
Of the 10 types of invertebrate eyes, how many of what eye type are there?
3x superposition (compound) 5x apposition (compound) 1x mirror 1x simple (camera type)
What type of eye does a fiddler crab have?
Apposition compound eye
Which eyes are more sensitive, apposition or superposition?
Superposition
What organisms have simple eyes?
Box jellyfish larva Polychaete larval ocellus Flatworm Inverse cup eye of planarian flatworm Lens eye of juvenile box jellyfish
How do pigments provide colour to organisms?
We see the colour of the reflected light. Pigment colour looks very different to organisms who have ultraviolet sensitivity - gives different areas different brightness
What do bifocal eyes allow?
Image separation
What is the difference between constructive and destructive waves?
Two constructive waves together intensity the colour, whereas two destructive waves together removes colour
How is structural colour produced?
Constructive interference creates the iridescent and metallic looking colours we see in beetles, fish and butterflies. The periodicity of the structure has to be about the same as the wavelength of light
What is periodicity?
The quality or character of being periodic; the tendency to recur at intervals
Example of structural colour - morpho butterflies (genus)
Nano-structured materials create multiple reflections that interfere with each other constructively. Morpho butterflies have scales with ‘christmas tree’ structures which cause structural interference and colouration. Adding water to a scale fills the air gaps and changes the refractive indices, therefore changing the colour
What percentage of the world population lives under light-polluted skies?
80% worldwide
99% in US and Europe
What is the angle of polarisation?
The mean angle at which electric fields of multiple waves oscillate
What is the degree of polarisation?
Describes how close the angles of the waves are to each other. If the degree of polarisation is 1, then all the electric fields are oscillating in the same direction
Measure of how much of light present is polarised
How do animals use the polarisation of light?
As a source of visual information
How do insects use celestial polarisation?
They use it for navigation - the angle of polarisation is always at 90 degrees to the direction of the sun
How does light pollution affect skylight polarisation?
It can mask polarisation, which can affect organisms which rely on skylight polarisation for navigation
What temperature do hyper-thermophiles live in?
80-110 degrees Celsius
Mainly bacteria and Archaea
What are Archaea?
Single-celled microorganisms with no nucleus or other membrane bound organelles which use sulphur instead of oxygen as an electron acceptor during cellular respiration
They are prokaryotes, and are of interest in industries for catalysis reactions and heat tolerant enzymes
Features of thermophilic bacteria
Similar use of sulphur in poor oxygen environments to archaea
High levels of saturation in lipids helps keep the membranes stable
What is the earlier evidence of life and what type of organism was it thought to be
Stromatolites - fossilised layers of thermophilic bacteria
What are ‘black smokers’?
Chimneys formed from deposits of iron sulphide, which is black
What is a hydrothermal vent?
A fissure in the planet’s surface from which geothermal heated water issues
What are ‘white smokers’?
Chimneys formed from deposits of barium, calcium and silicon, which are white
What can come bacteria oxidise?
Hydrogen sulphide
What animals make up hydrothermal vent communities?
Crustaceans and worms
What happens to vent crabs as they grow?
They lose the optics (focusing abilities) of their eyes as they grow, using only a flat retina
What can the temperatures in hydrothermal vents reach?
300-400 degrees Celsius
What is an example of a species with extreme drought tolerance?
Selaginella lepidophylla (desert plant)
What do Antarctic fishes possess that lower the freezing point of most of their body fluids below the freezing point of seawater?
Biological antifreezes
What is the freezing point of seawater?
-1.9 degrees Celsius
What must the antifreezes not do to the fish?
They must not substantially increase their osmotic pressure
Does antifreeze appear in Northern hemisphere fishes?
Yes, but only seasonally
What is the difference in volume of the hydrosphere compared to the terrestrial biosphere?
It is 10x higher
What are the uses of bioluminescence?
Predators use it for lure
Prey use it as an anti-predator defence
At what depth have snailfish been found?
7700m
How do deep sea eyes have greater sensitivity?
They are tubular eyes so have large lenses with a large collecting power
What adaptation does a spookfish have?
It has 4 eyes - 2 normally facing upwards and 2 downwards. The secondary eyes can act as a curved ‘rear view’ mirror and reflect light onto an accessory retina, producing an image. The mirror structure is a layer of crystals which are arranged optimally to shine light onto the secondary retina
How does the angler fish attract prey?
Using lures
Most deep sea fish have visual pigments sensitive to what wavelengths?
460-490 nm
How do dragon fish search for prey?
They use photophores under their eyes to produce a ‘search light’ for prey
Which species emits red-red light, which is invisible to other deep-sea animals? How is it able to see this red light?
Malacosteus niger
It enhances its long-wavelength sensitivity using a derivative of chlorophyll as a red light photosensitiser for the visual pigment
What are a common forms of camouflage in the deep sea?
Transparency
Pigmentation
Where are the majority of transparent species found?
In the pelagic region of the open ocean
What are examples of some transparent animals?
Medusae (polyp) Ctenophore (comb jellies) Polychaetes (annelids) Gastropods (snails/slugs) Fish
How does pigmentation work as camouflage?
Animals living at greater depths use red or black pigments for camouflage as red sensitivity is minimal in the deep sea
Where does transparency work best?
Where there is light - the upper mesopelagic zone as they can hide under diffuse downwelling illumination but not direct illumination
Why doesnt transparency work under direct illumination?
Reflections will give the animal away
What depth is the mesopelagic zone?
200-1000m
Why is there a shift to red and black pigmentation at deeper depths?
Silhouettes under downwelling light is not a problem as it is too dark, and blue bioluminescence must be absorbed to avoid detection
What is the depth of the the Bathypelagic zone?
1000-4000 metres
What can squid do to remain camouflaged?
They can alternate between transparent and producing a red pigment, depending on whether they are illuminated with blue light or not
What is a swim bladder?
Controls buoyancy - some deep sea fish have lost their swim bladder, whilst others can pressurise it to very high levels so it doesn’t implode
Up to what pressure can animals store pure oxygen in their swim bladder?
200 atmospheres - 2000m deep
What is the result of increasing the pressure on cell membranes?
Decreased fluidity - membranes turn gel-like
What are 5 lipids that deep sea animals have in their cell membranes?
Fatty acids Glycerolipids Glycerophospholipids Sterol lipids Sphingolipids
What type of fatty acids allows the membrane to remain fluid at high pressures or low temperatures?
Unsaturated fatty acids - increasing the level of unsaturation stops the membranes phase separating and some components going into a gel phase at high pressures
What is the name of the adaptation that allows cell membranes to maintain a functional state at temperatures or pressures that are too high or low and may cause the membrane to transition to a non-functional state?
Homeoviscous adaptation
What do different amino acid properties affect?
Compressibility - a shift in the amino acid sequence of the visual pigment changes the compressibility of the protein
What type of formula relates the compressibility of a protein with its amino acid sequence?
Empirical formulas - they can be used to determine if the compressibility of visual pigments of fish a cephalopods vary in animals that live deeper and at higher pressures
What is the correlation between depth and protein compressibility?
Protein compressibility negatively depends on depth - visual pigments in deeper-living animals are less compressible
What type of evolutionary mechanism has reduced the compressibility of visual pigments in many deep sea animals?
Convergent evolutionary mechanism
What is anthropocentric bias?
Humans think every living thing views the world in the same way that we do - humans are the centre of the universe
What are passive senses?
They collect information using available energy (e.g. sunlight, ambient sounds)
What are active senses?
They probe the environment with self-generated energy and analyse how the environment modified the outgoing energy
What do our senses perceive from electromagnetic waves?
Vision
Thermoreception
What do our senses perceive from mechanical stimuli?
Hearing Touch Acceleration Balance Pressure and current Proprioception Thermoreception
What is proprioception?
The unconscious perception of movement and spatial orientation arising from within the body itself
What do our senses perceive from chemical stimuli?
Taste
Smell
What do our senses perceive from electrical fields?
Electroreception
What do our senses perceive from magnetic fields?
Magnetoreception
Origins of information
Self/internal state
Environment and us in it
Others (including communication)
What must communication occur through?
A transmission medium
What are the costs of sending a communication signal?
Predation
Parasitism
Energy
Time budget
What are the costs of receiving a communication signal?
The same as when sending one, but particular emphasis on the time budget
When does communication occur?
When the benefits outweigh the costs
What result can occur from communication signals
They can trigger, stop or modify behaviour
What are 5 classes of meanings for signals? (important to learn)
- Announce species, sex, age or individual
- Broadcast presence and location
- Indicate current status of sender (activity, dominance)
- Change of status of social unit (warning)
- Near field interactions (private vs public)
What is bioacoustics?
The scientific study of biological sounds
What are 8 examples of areas studied in bioacoustics?
- Animal acoustic communication
- Sound production in animals
- Sound propagation in water, air, etc.
- Sound reception capabilities
- Evolution and development of acoustic behaviour
- Animal sounds and their environment
- Biosonar or echolocation
- Effects of man-made sounds on animals
Why are sounds such useful signals?
Work in darkness Work when out of sight Omnidirectional Good for localisation (phonotaxis) Signals can be adapted to needs
How can sound signals be adapted to needs?
Can over a range of desired distances
Can be switched off
Can be honest signals for partner selection
Can carry many meanings
What does sound need to travel?
A medium such as air or water
How to sound waves travel?
They oscillate medium particles relative to their resting position
What two types of sound waves are there?
Longitudinal wave
Transverse wave
What do longitudinal waves travel through and what is their oscillation direction?
They travel through air and water
Their oscillation direction is back and forth
What do transverse waves travel through and what is their oscillation direction?
Through solids
They oscillate up and down
Sound involves two separate speeds - what are they?
The propagation speed of the wave - the speed of sound (->)
The speed of the oscillating wave - particle velocity ( or up and down)
What is the speed of sound (c) in air and water?
Propagation speed in air is 340 m/s
In water 1500 m/s
What is the particle velocity (v) of air and water
Oscillation speed
In air depends on amplitude
In water it is very low - up to 16 m/s
What is phonotaxis?
The movement of an organism in relation to a sound source
How loud is sound?
This relates to sound pressure (p)
It is measured as a change in local pressure in Pascal (Pa)
What is ambient atmospheric pressure?
101,325 Pa
What do sound pressure oscillations vary between?
20 micro-Pa to 63 Pa
The higher the pressure oscillation amplitude (A), the…
louder the sound
Louder sounds oscillate…
faster
What is the loudness of a sound measured in?
Decibels (dB) - uses small numbers for sound pressure
How is the decibel calculated?
- Setting zero as the human hearing threshold - 20 micropascals
- Logarithmic scale
20 * log10 (Pmeas/Pref)
Pmeas = measured sound pressure
Pref = threshold sound pressure (20 micropascals)
What is our hearing threshold in dB SPL?
0 dB SPL
What is SPL?
Sound pressure level
What is the smallest change that we can perceive as being different?
approx 1 dB
A sound gets twice as loud when it’s sound pressure double, which means it’s sound pressure level has increased by…
6 dB
What is the equation to work out the frequency (Hz) of a sound wave?
f = 1 / T (sec)
What is the equation for wavelength?
wavelength = c / f c = speed of sound f = frequency
What is the human hearing range in Hz?
20-20,000 Hz
What is a visual representation of a sound called?
Spectrogram
What are on the x and y axis of a spectrogram?
x = time (ms) y = frequency (kHz)
What are the two classes of animal sounds?
Mechanical sounds
Respiratory sounds
Where are mechanical sounds derived from?
Movements (wings, legs, etc)
Thermoregulation (shivering, etc)
Food processing (tongue clicking, grinding, etc)
Mutual contact between body parts
Interaction between body and some element of the environment
What are the two classes of respiratory sounds?
Nonvocal (breathing noises)
Vocal (vocalisations)
What is stridulation?
The act of producing sounds by rubbing together certain body parts
Describe the stridulation of grasshoppers
One vein of each forewing has file bearing ridges. The scraper is on the hind leg
Fast leg movements make the file and scraper rub against each other, vibrating the wings
Male songs are species-specific and match female preferences
Describe stridulation of crickets and bushcrickets
In the wings there is a file with 50-300 ridges. To sing, the scraper of the other wing touches the file
Rubbing file and scraper against each other when opening and closing the wings vibrates the wings
Resonating areas of the wing (mirror and harp) amplify the sound
Pure tones are produced
Describe the stridulation of mole crickets
Method of stridulation similar to crickets. Wings resonate.
Hollow abdomen resonates thereby amplifying the sound.
Male builds complex singing burrows. The size of the chamber is such that it resonates at the song’s frequency.
The entrance of the burrow is horn-shaped which increases sound propagation efficiency
What is a tymbal?
A corrugated exoskeletal structure used to produce sounds in insects
Describe how the cicada uses tymbals
Contracting the internal muscles produces a clicking sound as the timbals buckle inwards.
When the timbal muscles relax, the timbal returns to its original position producing another click.
Air-filled cavities in the abdomen amplify the sound through resonance
Why family of fish communicate by grinding their teeth and are highly vocal?
Pomadasyidae (grunts)
What family of fish communicate using repetitive drumming or throbbing sounds and are highly vocal?
Sciaenidae (drums or croakers)
What is a species of seahorse which uses stridulation to communicate during the mating process?
Hippocampus erectus
Hippocampus hudsonius
Rubs skull against bony crest called a coronet by raising and bowing its head, producing clicking noises
What fish communicates by drumming on its swim bladder?
Haddock (Melanogrammus aeglefinus)
What fish communicates by releasing air from its anus?
Herring (Clupea harengus)
How do snipe communicate?
They have an in-flight ‘drumming’ or ‘beating’ display
The sounds are caused by outer tail feathers
What is the Latin name for a snipe?
Gallinago gallinago
What is the Latin name for the club-winged manakin?
Machaeropterus deliciosus
How do manakins produce sound?
Display sounds produced by rubbing their wing feathers together
How does the leafhopper produce sound?
Use substrate vibrations for communication signals. Small vibrations of the plant can be made audible to humans by laser vibrometry
How do hares/rabbits produce sound?
Use their hing legs to thump the ground as a warning signal. This sound is both substrate and airborne. This behaviour has been ritualised from jumping to cover
What is ritualisation?
The evolutionary process by which an action or behaviour pattern in an animal loses its original function but is retained for its role in display or other social interaction
How do woodpeckers produce sound?
They drum on tree trunks. This is an airborne signal
How to chimpanzees produce sound?
Drum on tree trunks
Where are sounds produced in mammals? What kinds of sounds are produced?
Mammalian larynx
Produces sounds rich in overtones
How does the Indri (Indri indri) communicate with sound?
Two individuals in duet
Fundamental frequencies = approx 750 Hz and approx 1100 Hz
Many harmonic overtones (their frequencies are integer multiples of the fundamental frequencies)
How do African elephants communicate?
One greeting rumble
Fundamental frequency approx 15-20 Hz
Many harmonic overtones
What is the Latin name for the African elephant?
Loxodonta africana
What does the vibration frequency of a land mammal’s vocal folds depend on?
The length of their vocal cords
What is a land mammal’s voice box proportional to?
The length of the animal
The larger the animal, the … the vocal fold vibration
Slower
What is the connection between frequency of calls and size of animal
The bigger the animal, the lower the frequency of their calls
How do hippos communicate with calls?
2 vocal elements Fundamental frequency approx 190 Hz Many harmonic overtones Also possesses breathing elements with no harmonic structure Audible under water!
How do humans communicate?
3 vocal vowels: ‘a’, ‘ou’ and ‘i’
Fundamental frequency approx 100 Hz
Many harmonic overtones
Formants (overtones with the most energy)
Consonants ‘c’, ‘st’, ‘c’ and ‘s’ with no harmonic structure
What sound-producing structure do birds have and how is it structured?
Syrinx
Has 2 vibrating valves
Birds have independent control of both sides, so can produce two different sounds at the same time and they can alternate between them
Different frequency ranges on both sides
What is the Latin name for the linnet and what are the properties of its calls?
Acanthis cannabina
Highly complex song
Harmonic elements
Changes in fundamental frequency from note to note
What is the Latin name for the brown-headed cowbird and what are the properties of its call?
Molothrus ater Very rapid cluster of notes Right syrinx produces high frequency notes Left syrinx produces low frequency notes Sweeps switch between sides
Why is sound production even more important in water?
Can be too dark for vision
Olfaction hampered by slow diffusion
What are the two purposes of sound in water?
Communication
Orientation (biosonar)
What do baleen whales use sound for underwater?
Only communication
What do toothed whales use sound for underwater?
Communication and biosonar
What type of whale is a humpback whale and what is its latin name?
Baleen whale (Mysticeti) Megaptera novaeangliae
How do humpback whales communicate?
Makes can song for hours Repetitive elements New song every year, sung by all males Have larynx but no vocal chords Sound production mechanism unclear
What problem do humpback whales experience and what is their solution?
Air compression at greater depth and thus limited air supply
Solution: recycle air - no bubbles produced (alternation in elements)
What type of whale is a bottlenose dolphin and what is its latin name?
Toothed whale (Odontoceti) Tursiops truncatus
How do dolphins communicate?
Larynx missing in all toothed whales
Sound production with phonic lips in nasal airway (near blowhole)
Produce individual clicks used in communication and echolocation
What does impedance measure?
The closer the impedance of two media, the better sound passes from one medium to another
What is the impedance ratio of air : water?
1 : 3600
Almost no airborne sound enters water and vice versa
How is impedance calculated?
Density (p) x speed of sound (c)
What is beam forming in air?
The shape of the mouth determines it’s sound radiation pattern. This makes it easy to modify air, because sound is reflected by body tissue
Beam forming under water
Because body tissue and water have very similar impedance, sound in water passes right through body tissue.
However, air-filled cavities can reflect sound, as can oily/fatty tissue with a density differing to water. These can be used to manipulate underwater sound
What are some adaptations to manipulate sound underwater?
Melon in dolphins
Nose in sperm whales
Double chin of hippopotamus
What is spherical spreading loss?
With increasing distance from the source of a sound, the acoustic energy is spread over larger areas
What is energy change proportional to?
Sound pressure
For every doubling of distance, …
sound pressure halves and sound pressure level drops by 6 dB accordingly
What is frequency-dependent absorption?
Air absorbs sound energy. High frequencies are more strong absorbed than low frequencies
What frequencies do animals use for long range signalling?
Low frequencies
Why do birds sing in the morning?
The speed of sound increases with temperature. In a layered atmosphere (with air layers of different temperatures), sound propagation is no longer linear. When it is warmer higher up, c increases with height and sound is directed back to the ground. When it is warmer at the ground, c decrease with height, and sound is directed up and away
What does the speed of sound in seawater depend on?
Salinity
Pressure
Temperature
How do humpback whales communicate over such long distances?
There are particular layers of water of a certain temperature and pressure, which can trap their calls, meaning less energy is lost as the sound spreads not spherically but in a disc shape. They also use very low frequencies, and water has a low absorption
How do forest elephants communicate?
Elephant societies are based on long-range infrasound communication (over miles)
How do forest elephants solve the problem of trees blocking their calls from propagating?
Diffraction bends sounds around objects, but only when the wavelength is longer than the object size. Forest elephants can communicate through dense forests with their low frequency (long wavelength) sounds
What is infrasound?
Sound waves with frequencies below the lower limit of human audibility
What is the wavelength of an elephant’s rumble?
wavelength = c / f
330 m/s / 25 Hz = 13.2 m
How do invertebrates detect substrate-borne sounds?
Substrate vibrations move haemolymph in the legs of insects. This is picked up by the subgenual organ in the tibia of each leg. This is found in ALL insects, and allows substrate based communication
How do invertebrates detect air-borne sounds using sensillae?
Hair-like sensillae are found in insects
In arachnids there are trichobothria
These follow the particle movement in air, and have mechano-sensory cells at their base
What organ is located at the base of fly antennae and how does it function?
Johnston’s organ - highly sensitive detector of antennal movement
Mosquitoes hear the flight noise of females
What are tympanal ears?
Measure sound pressure
Have evolved separately many times in insects
Ears located at many different body parts
Often sensitive to ultrasound to evade bat predation
How is the mammalian ear structured?
Pinna collects and funnels sound
Sound waves vibrate the tympanic membrane
Ossicles (malleus, incus, stapes) of middle ear transfer vibratory motion of eardrum to oval window of inner ear inducing pressure waves in fluid of cochlea
Pressure waves detected in cochlea by receptor cells in Organ of Corti
How do toothed whales receive sounds underwater?
Toothed whales have no outer and middle ears and no eardrum.
Sound is picked up by their lower jaw
Fatty tissue as well as their teeth seem to be involved
Sound conducting tissue leads sound to their inner ear
Why is the function of inner hair cells?
When deformed, hair cells change the rate of neurotransmitter release, which then affects the number of action potentials generated by the sensory neurone
What is the function of the cochlea (inner ear)?
The pressure wave entering the oval window vibrates the basilar membrane and the organ of Corti. This leads to the deformation of the hair cells, and action potentials in neurones
Where in the cochlea are low frequency sounds best detected?
Apical end of cochlea
Where in the cochlea are high frequency sounds best detected?
Basal end of cochlea
What is the function of outer hair cells?
Outer hair calls are not sensory but mechanically active - they change their length with frequency characteristic for their position along the cochlea. They amplify the weakest sounds
What is interaural time difference (ITD)?
Interpreting the time difference between when a sound reaches one ear compared to the other
When sounds come from straight ahead, which ear should the reach first?
Both ears at the same time
When doesn’t interaural time difference work?
When a sound starts quiet and gets louder
What is interaural intensity difference (IID)?
When your head creates an acoustic shadow so one ear may hear sound more quietly as a result
When is there no acoustic shadow?
When the wavelength of the sound is greater than the size of the head
What is an adaptation many animals have for acoustic gain?
Pinna directionality - they can rotate their pinna towards the direction of a sound
What are interaural spectral differences?
Some signals are reflected when they enter the ear, causing negative and positive interactions of sound waves. Some waves will cancel each other out, but interference creates direction-specific spectral notches. The brain uses the location of spectral notches in both ears for certain sounds to find the location of the original sound in space
How to increase ITD and IID the gain:
Using acoustic locator systems to make your head/ears ‘bigger’ e.g. a sound horn
In spectrograms, what do diagonal lines signify?
Frequency changes over time
What is biosonar?
Analysis by an animal of the echoes of its own emitted sound waves, by which it builds a sound-picture of its immediate surroundings
What does biosonar provide animals with?
Gives animals access to habitats with insufficient ambient light for vision - they can localise objects (distance and direction)
What animals produce clicks during echolocation?
Egyptian Fruit Bat clicks its tongue
Oilbirds (South America)
Swiftlets (Asia)
all 3 breed in caves
What animals use laryngeal echolocation?
Toothed whales
Echolocating bats
How do dolphins use echolocation to dig for prey?
Sound in water penetrates body tissue, sand and silt
However, bones and swim bladders give echoes, so dolphins can detect buried fish
What two types of emitters do bats have for beam forming?
Oral emitters
Nasal emitters
What do oral emitters produce?
Broad beams
What do nasal emitters produce?
Narrow beams
Horizontal beams are produced by the interaction between nostrils
Vertical beams are produced by the action of the noseleaf
What happens if you block on nostril of a bat?
They cannot localise sound
As bats approach a target, what happens to the inter-call intervals?
The inter-call intervals are reduced as once the bat has heard the echo of interest, it can produce another one, and as it is closer to its target the echoes return more rapidly
What is the relationship between the delay between sound emission and the target and the distance of the target?
The shorter the delay between sound emission and echo reception, the closer the target
Why bats have trouble hearing echoes whilst calling?
The echoes of objects in the signal overlap zone (SOZ) are masked by the call
How do bats combat the problem of being unable to hear echoes whilst calling?
Bats shorten the call duration accordingly when approaching a target
What volume can bat calls reach?
133 dB SPL in 10 cm
Threshold of pain 140 dB
How do bats prevent damaging their own ears with their calls?
Temporary deafness caused by muscle contraction - the most rapidly working muscle known
What are the features of aerial-hawking bats?
Catch flying insects
Biosonar used for finding and getting food as well as orientation
Very loud calls give long detection range
Smaller ears because fast fliers
What are active gleaners?
They find motionless, silent prey sitting on a substrate based only on their echo signature. Amazing echo-acoustic resolution.
Weak or loud calls for orientation and food detection
Insectivores, carnivores, frugivores, nectarivores
What are passive gleaners?
Locate prey by their walking noises or communication signals. Weak calls only for orientation.
Large ears
Eat insects, arachnids (including scorpions), vertebrates (including frogs)
