ECHOLOCATION IN BATS, CETACEA & SIRENIA Dr. Rupa Mukhopadhyay

WHAT IS ECHOLOCATION ? Echolocation is the use of sound waves and echoes to determine where objects are in space. Echolocation, also called bio sonar .

THE PROCESS OF ECHOLOCATION Ranging is done by measuring the time delay between the animal's own sound emission and any echoes that return from the environment. The relative intensity of sound received at each ear as well as the time delay between arrival at the two ears provide information about the horizontal angle (azimuth) from which the reflected sound waves arrive.[7]

ECHOLOCATION SYSTEM IN BAT (EAR -2) (EAR -1) (MOUTH)

ECHOLOCATION SYSTEM IN WHALE

DOPPLER SHIFT AND ECHOLOCATION

PROBLEMS ENCOUNTERED DURING ECHOLOCATION ECHOLOCATION JAMMING – Jamming occurs when non-target sounds interfere with target echoes. Jamming can be purposeful or inadvertent, and can be caused by the echolocation system itself, other echolocating animals, prey, or humans

TYPES OF JAMMING Self jamming - jamming occurs when an echolocating animal produces many sounds in succession and assigns an echo to the wrong emission. Jamming by other echolocation systems - Like electric fish, echolocating animals are susceptible to jamming from other animals of the same species emitting signals in the nearby environment.

TYPES OF JAMMING Jamming by prey -  the tiger moth Bertholdia trigona produces clicks at a very high rate (up to 4,500 per second) to jam bat echolocation. Humans jamming animals - buildings or bridges, or wind turbines where large numbers of bat mortalities occur due to problem in echolocation.

Mechanisms to avoid jamming Production of progressively shorter sounds . waiting enough time for echoes to return from all possible targets before making the next sound .  jamming avoidance response (JAR) to avoid jamming by other animals . scaling up acoustic deterrents to large volumes for applications because of the high atmospheric attenuation of ultrasound.

JAMMING AVOIDANCE RESPONSE (JAR) In a JAR, one or both animals change the frequency of their sounds away from that used by the other animal.  This has the effect of allowing each animal a unique frequency bandwidth where jamming will not occur. Bats can make this adjustment very rapidly, often in less than 0.2 seconds.