MAR 370: Exam 3 Review

Polygynous Mating Systems in Mammals-Lekking -Resource Defense -Female Defense -Sequential Female Defense -Scramble CompetitionLekkingThe gathering of males in an area for the purpose of displaying to attract females (ex: walruses)Resource Defense PolygynyMales defend territories rich in resources that are used by and attract females (ex: most Otariids)Female Defense PolygynyMales monopolize aggregations of females directly (ex: elephant seals)Sequential Female DefenseMales defend single females directly (ex: hooded seals)Scramble Competition-Males search opportunistically for estrous females -Males spend time trying to mate with as many females as possibleFemale Mate Choice in Pinnipeds-Choice of site on breeding beach -Choice of location in harem -Eliciting inter-male competition -Courtship behavior toward preferred malesPolygynous Mating Systems in Cetaceans-Sequential Female Defense: Sperm Whales, Bottlenose Dolphins -Lekking: Humpback Whales (?) -Scramble Competition: Killer Whales, Pilot Whales -Many Species: Sperm CompetitionSexual Dimorphism (Odontocetes)Male and female odontocetes can differ in: -Size (ex: sperm whales) -Shape (ex: orcas, eastern spinner dolphins, spectacled porpoises) -Cranial morphology (ex: Northern bottlenose whales) -Dentition (ex: narwhales, Blainville's beaked whales)Social Behavior of Resident Killer Whales-Highly social -Cohesive pods -Permanent Matrilineal Groups -Up to 4 generations -Neither males nor females disperse from their natal groupsSocial Behavior of Pilot Whales-Permanent Family Groups -Neither sex disperses from their natal pods -Pods are strongly matrifocal -Pods occasionally merge -Males do not father offspring within their own podSocial Behavior of Bottlenose Dolphins-Fission-Fusion Societies -Communities: dolphins in an area that periodically associate with one another -Groups: temporary aggregations of dolphinsLong-Term Studies of Bottlenose Dolphin Social Behavior-Sarasota, Florida (Randy Wells) -Strong mother-calf relationships -Long-term male pair bonds -Shark Bay, Western Australia (Richard Connor & Janet Mann) -Coalitions and super alliances -Bahamas (Diane Claridge) -Moray Firth, Scotland (Ben Wilson & Paul Thompson) -Doubtful Sound, New Zealand (Liz Slooten & Steve Dawson)Humpback Whales-Feeding grounds: usually unstable associations, but largely untested -Breeding grounds: short-term associations with frequent agonistic interactions amongst males related to breeding access-competitive groupsSperm Competition-Sperm of different males compete to fertilize ovum -Females mate with multiple males during estrous -Selection will favor males with capacity for large volumes of sperm -Little advantage to large body size in males pursuing this strategyWhat are some uses animals have for sounds?-Communication -Finding Food -Detecting Predators, Prey, Competitors, and/or Mates -ReproductionSensory Modalities in Water vs. AirAcoustic: -Range 10-100 km; Speed 1500 m/s in water -Range 1 km; Speed 340 m/s in air Light: -Range 1-100 m; Speed 2.25 x 10^8 m/s in water -Range 1-10 km; Speed 3 x 10^8 in air *Marine mammals are specialized for using sound underwaterWave Parameter Definitionsl = wavelength [meters] T = period [seconds] = 1 / f f = frequency [cycles / s] or [Hertz] or [Hz] 2 p radians = 1 cycle = 1 revolution w = angular frequency [radians / s] = 2 p f = 2 p / T c = wave speed [m/s] c = l fSpeed of SoundIn air = ~ 342 m/s In water = ~ 1530 m/sHumans can hear from...20 to 20,000 Hz Ultrasonic > 20 kHz Infrasonic < 20 Hz2 Major Divisions of BioacousticsPassive: reception only [HEARING] Active: production and reception [ECHOLOCATION]Distinguishing Characteristics of Sounds-Time -Many animals make repeated sounds, and we can get information by studying those repetition patterns. -Intensity -Measure of the loudness of a sound. -Frequency -Most sounds are made of many frequencies.Acoustic ResistanceThe product of the medium's density and sound speed acoustic resistance = r * c This is a way of describing how "difficult" it is to create a pressure wave in the mediumIntensity= pressure^2 / (density * soundspeed)Definitions and UnitsPressure: Newton/m^2 or (kg m /s^2)/m^2 or Pascals Density: kg /m^3 Soundspeed: m/s Intensity: Joule / ( s m^2) OR Watts /m^2 Energy: Joule = kg m^2/s^2 Power: Watts = Joule/sDecibelsLogarithmic unit to express the ratio of two quantities Often used for power or intensity *You always need to provide a reference level when reporting a dB quantity Sound measurements in air usually use 20 mPa Sound measurements in water usually use 1 mPaAmplitude (Loudness)The amplitude of a sound wave is characterized by its sound pressure level (SPL) Sound Pressure Level (SPL) is measured on a logarithmic scale using the decibelSound AttenuationDiminution of sound intensity as energy spreads over progressively larger areas *High frequencies attenuate much more quickly than low frequenciesSound IntensityAcoustic power of a sound per unit of area in relation to a fixed referenceWays to categorize sounds:-Constant Frequency (CF) [pure tone] -Frequency Modulated (FM) [whistle] -Broadband [snap, clap]SpectrogramPlots of frequency vs. time, like musical notationEcholocationThe ability to orient by transmitting sound and receiving echoes from objects in the environmentProcesses of Echolocation1. Sound production 2. Sound reception 3. Signal processingSource of Echolocation SignalsPrevious hypothesis: Larynx (Purves & colleagues) Current hypothesis: Nasal Sacs (Norris & colleagues) Phonic Lips / Dorsal Bursae ComplexOdontocete Cranial Anatomy-Cranial Asymmetry -Melon -Complex Nasal SacsMelon-Hypertrophied fatty forehead present in all Odontocetes -Comprised of metabolically inert fatty acids -Functions to shape or focus the emitted sound beamSperm Whales-Spermaceti organ -Bathtub cranium -Sounds produced at the front of head -Reflected by skull, refracted by spermaceti organThe number, source level, and time interval between clicks vary with:-Size of Object -Distance to Object -Background Clutter *Outgoing clicks occur between returning echoes to reduce interferenceBottlenose Dolphin Echolocation-Target Detection -Target DiscriminationNarrowband, High Frequency Clickers-Live in shallow (nearshore), "cluttered" waters -Small body size ex: Harbor porpoises, Hector's dolphinsCosts of EcholocationInter-specific Interception: Alerting predators; alerting prey Intra-specific Interception: Alerting competitorsPassive Listening HypothesisDespite their sophisticated echolocation system, bottlenose dolphins echolocate sparingly Bottlenose dolphins frequently prey on soniferous (sound-producing) fish The passive listening hypothesis suggests that these animals passively listen (rather than actively echolocating) to detect their preyEcholocation in Killer WhalesResident Killer Whales: -Feed on salmon -Frequent echolocation Transient Killer Whales: -Feed on mammals -Infrequent echolocationModes of Communication-Chemical -Electrical -Tactile -Visual -AcousticSound ProductionOdontocetes: -Echolocation clicks produced by the PL/DB -Whistles produced in the larynx Mysticetes: -Low frequency pulses -Sounds produced in the larynx Pinnipeds: -Produce sounds in air and underwater -Sounds produced in the larynx Sirenians: -Sounds produced in the larynxCase Studies of Cetacean Vocal Communication-Humpback whale -Fin whale -Killer whale -Sperm whale -Bottlenose dolphinCosts & BenefitsNeutral: Benefit to both the sender & receiver Manipulation: Benefit to the sender & cost to the receiver Eavesdropping: Benefit to the receiver & cost to the senderProposed Social Functions of Cetacean Vocalizations-Reproductive advertisement (ex: humpback whales) -Long-range communication (ex: fin whales) -Group recognition (ex: killer whales) -Individual recognition (ex: bottlenose dolphins(?)) -Referential communication (ex: sperm whales)Humpback Whale Songs-Complex series of repeating units, phrases, themes -Frequencies in our hearing range (up to 2 kHz) -Can last up to 20 min -Changes dramatically over time (old themes are not re-used) -Produced mostly by males -Produced mostly on the breeding grounds -Changes matched by all males -Correlated with male-male interactionsFin Whale Sounds-Low frequency (~ 20 Hz) -Could theoretically travel long distances -Utilizes SOFAR channel(?) -Produced seasonally near Bermuda -Likely used in reproductionSOFAR ChannelSound speed reaches a minimum at around 600-1200 meters Speed increases as temperature and pressure increase Minimum velocity layer is called the SOFAR channel Loud, low frequency noises made at this depth can theoretically be detected for thousands of kilometersKiller Whale Groups-Killer whales off of Vancouver Island live in the most stable groups documented for ANY mammal -Each pod has its own specific "suite" of vocalizations, referred to as dialects -Group-specific vocalizations that function in group recognitionNorthern Resident Acoustic Clans-Different groups distinguished by the communication sounds they produce -These dialects provide clues about the relationships of groups and populations -Each group produces a specific number and type of discrete calls -Each pod has a unique dialect that can be readily identified -Within the resident population, pods with related dialects belong to a clan -Different clans have no dialect features in commonSperm Whale Vocalizations-Produce rhythmic vocal patterns called "codas" -Some appear to be individually specific -Some appear to be group specific ("shared codas")John C. Lilly Bottlenose Dolphin Study-Early researchers looked for context-specific vocalizations -No supporting evidence found -Studies hindered by not knowing which individual dolphin in a group was making a sound -Studies lacked objectivityNatural SoundMany natural processes (especially wind, waves, and seismic events) in the ocean also make sounds and these can be very loud and continuous as wellZone of Sound InfluenceIn order of most to least damaging: 1. Injury - Acoustic Trauma 2. Hearing Loss - Permanent threshold shift 3. Temporary Threshold Shift 4. Avoidance, Masking 5. Behavioral disturbance declining to limits of audibilityAnalog vs Digital SignalsAnalog signals are continuous. [don't lift pencil] Digital signals are discrete. [have to lift pencil] Digital signals provide a lot of benefits: -exact copies can be produced -easier to transport/distribute But they are limited in: -they are a sub-sample of the "true" signal -by definition can not contain ALL the information of original signal -require ADC (analog-to-digital converter) and DACSamplingThe process where a continuous (analog) signal is converted to a discrete (digital) signal Has two key parameters (Sampling Rate and Quantization)Sampling RateThe separation (in time) of where the signal is sampled A higher sampling rate will better recreate the signal, but requires more data storageNyquist FrequencyUpper bound on the frequency content of a signal being sampled Equal to 1/2 the sampling frequency In practice this means you must sample your signal at a rate TWICE that of the highest frequency component you are interested inQuantizationHow accurately you measure the amplitude of the original signal when you sample it Digital signals are recorded as a binary value (0 or 1) The number of values a signal can be assigned is a function of the number of bits (binary digits) used (2^n) With a two bit quantization, you can have 4 possible values: 00, 01, 10, and 11 With a 3 bit quantization, you can have 8 possible values: 000, 001, 010, 011, 100, 101, 110, 111Calculating File SizesFile Size = (sample rate * # of channels * (bits per sample / 8) * duration ) = # bytesDuty Cycle% of time we are recording It is impractical to record 100% of the time Can be simple (1 min ON, 1 min OFF) or complex, and will depend on recording system capabilities