Bats Flashcards
Describe the calls of bats found in an open habitat.
Mainly Constant frequency calls
Lower frequency
Longer calls
= projection over longer distances
Describe the calls of bats found In a closed habitat.
Mainly Frequency modulated calls
Higher Frequency
Shorter calls
= detection of local objects
Describe the calls of aerial hawking bats ?
Very loud calls
Insects are widely dispersed so require large detection range
What is the prey of aerial hawking bats ?
Flying insects
What behavioural characteristic do all bats use ?
Use scooping motion of the tail membrane to capture prey and prevent its escape.
How do Aerial hawking bats use Biosonar ?
For food detection and orientation.
Describe the ears of aerial hawking bats.
Small, are fast fliers so need to be streamlined.
How do passive gleaners locate prey ?
Via walking noises or communication signals between insects
Describe the calls of the passive gleaners,
Weak- only used for orientation
Do not want to mask prey.
What is the prey of passive gleaning bats ?
Insects, arachnids, scorpions, vertebrates, frogs.
Describe the ears of passive gleaning bats.
Large ears- to locate prey source.
Describe how active gleaners locate prey
Locate motionless & silent prey using echolocation.
What is highly specialised about active gleaners ?
Amazing echolocation resolution.
Describe the calls of active gleaners.
Weak or loud calls to detect prey and orientate.
Become fainter as approach prey
What type of diets do active gleaners have ?
Can be insectivores, carnivores, frugivores, nectarvores.
Describe the beam emitted by oral emitters.
Broad beam
Describe the beam emitted by nasal emitters
Narrow beams
What type of emitter are the majority of bat species ?
Nasal emitters
What is the advantage of being a nasal beam emitter ?
Can chew prey item at same time as echolocating
What is the role of the nostrils in beam formation ?
The 2 nostrils narrow the sound beam to give directionality of the beam.
Why do bats reduce their inter call intervals when approaching a target ?
They only produce next call when the echo of interest has been heard.
Therefore can reduce time between calls on approach as echo occurs quicker
What indicates the distance/range of the target ?
The delay between the sound emission and reception.
Give the formula for range (distance).
Delay * C/2 (m)
C- speed of sound
What Is the resolution of bat calls ?
How well they can detect an organism.
Between 5mm and 0.3 mm
What are the issues with the signal overlap zone ?
Reduces the ability to detect an echo.
Why do bats reduce call duration when approaching a target ?
Shortens the Signal overlap zone. Enabling accurate detection of close range prey.
What is echo call overlap ?
If the prey item is too close to the echolocating bat.
‘In signal overlap zone’
The echo will return before the call is finished, creating overlap
Give the formula for calculating the signal overlap zone.
Call duration * Ca/2 (m)
C- Speed of sound in air
Bat calls can be very loud.
True or false ?
True, up to 133 dB
permanent damage- 140 dB
What are the problems with these loud bat calls ?
Bats could deafen themselves by their own calls.
How do bats prevent deafness ?
Create temporary deafness, by muscle contraction
Protection up to 200 Hz.
(most rapidly working muscle)
