Communication and Echolocation

Types of Communication

1.) visual

2.) auditory

3.) chemical

4.) tactile

Visual Communication

Communication through displays (less ambiguous), movements (show intention), and autonomic responses (piloerection- hair standing up)

Possible functions for displays of strength and health:

– Warning conspecifics
– Social cohesion
– Confusion effect
– Pursuit deterrence

Auditory Communication

Communication through sound signals for contact, boundaries, and recognition

Chemical Communication

Communication using pheromones, allomones, urine, and feces

Chemical Communication: Urine and Feces

– Contain metabolic wastes that serve as chemical signals
– Deposit at specific sites - territories
– Indicate physical condition - estrus

Chemical Communication: Reproduction behavior

• Reproductive behavior influenced by smell
Vomeronasal organ or Flehmen

Vomeronasal organ

branch of the nasal epithelium that forms a pocket that may open to the mouth cavity - important for detecting sexual pheromones

Flehmen

a behavior exhibited by mammals, that involves curling the upper lip and inhaling with the mouth open. This behavior exposes the vomeronasal organ to a scent or pheromone.

Tactile Communication

Communication through precopulatory behaviors and grooming for social bonds

Pheromone

Chemical substance affecting behavior or physiology of the same species

Allomones

Chemical compounds altering behavior of a different species

Echolocation

High-frequency sound pulses help to navigate and sense objects: give same amount of info as sight
• Bats: Sound produced by larynx (like we do); reflected sound (echo) may be picked up by the bat.

Limitations of Echolocation

Sound is attenuated (lost) rapidly in air.

spreading loss: loss from dissipation of sound away from source

absorptive loss: sound absorbed by atmosphere (curved lines)

Frequency

Sound pitch measured in Hertz, determining cycles per second

Amplitude

Sound intensity measured in decibels (dB) relative to pressure

What is sound?

Mechanical vibrations transmitted by an elastic medium. 

How do mammalian ears receive sound?

1. Sound pressure waves vibrate tympanic membrane and vibrate it.

2. Vibrations are transferred across the middle ear by the three ear ossicles.

3. The vibrations transmitted to fluid-filled inner ear at the oval window.

4. High frequency vibrations (waves) travel further down cochlea.

5. Hair cells in the cochlea are stimulated by the waves and the pattern.

Bandwidth

Range of frequencies produced in echolocation signals

Spermaceti Organ

Organ containing spermaceti for focusing echolocation signals

Echolocation in Cetaceans

Underwater echolocation using single clicks for detection and multiple clicks for communication

Sound Production

Sound produced in nasal sac system for echolocation

Sound Reception

Echoes received via mandible, channeled to auditory bullae for processing

High/Low Frequency Limitations

High frequencies reflect off small objects, low frequencies bend around small objects

Human/Bat Hearing Range

Humans: 20 Hz-20 KHz; Bats: 20 KHz-200 KHz

Echolocation Modulation

Narrowband (CF) for target detection, broadband (FM) for pinpointing targets

Echolocation in Shrews & Tenrecs

Terrestrial mammals echolocating with unique audible clicks and ultrasonic squeaks