Echolocation In Microbats
Ultrasound Foraging in Microchiroptera
Adaptive ValueWhat is adaptive value you ask? Adaptive value is, quite simply, the reason that a behavior has developed, resting upon the assumption that all behaviors develop to benefit an organsim. What does the behavior do for the animal that performs it? What does the performer have that the non-performer does not? Wikipedia: Adaptation
Echolocation in microbats facilitates a means of navigation similar to that of sonar in submarines. By using echolocation, the microbats are able to inhabit environments that might stymy and otherwise more adept creature. As such, bats are able to roost and inhabit caves and other dark but otherwise warm locations that are very effective as shelter.
All echolocating bats can be broadly charaterized as either shouting or whispering bats. Shouting bats tend to emit much louder noises in the (if we could hear it) 110 decibel range, which is roughly equivalent to the volume of a smoke alarm. These bats tend to occupy, navigate, and forage in large, open spaces. Whispering bats produce sounds at volume of human conversation, about 60 decibels. These bats are more suited to forraging in confined spaces such as tree foliage and dense forest interiors.
Bats can see as well as a human, but far more valuable than their sight is their echolocation in foraging. With the exception of megabats which are generally fruit eaters and of vampire bats and other such endcases, microbats tend to base their diet almost entirely on flying insects. Echolocation in many bats is so precise that it can detect an object the width of a human hair. With this power to vector and distance locate objects, a flying bat may eat up to 50% of its body weight in insects every night, and nursing females may either their entire body weight (about 4500 insects average).
Moths are a very common food for the echolocating microbat, and as such experience strong selective pressure towards the evasion or confusion of bat echolocation. Many moths have developed evasive tactics and physical adaptations that help to avoid the echolocation of bats. Some have evolved furry wings that don't reflect bat echolocation pulses. Other moths have developed sensitive membranes that can 'hear' echolocation pulses and when such pulses are detected the moths may fly in erratic patterns or fold their wings and dive to confuse their hunters.
Some bats have evolved to counter the above evasions. Some produce pulses that reflect off of fuzzy wings, while others use echolocative frequencies beyond the range of insect hearing. Still ofthers confuse insects by flying erratically. Bats have also 'learned' other means of catching insects on the win besides their mouth. They can also scop insects out of the air with a cupped tail or wing membrane and then reach down mid-flight to snatch the insect with their mouth. This means of feeding leads to very erratic flight, but results in more successful feeding.