Species distinctions: Bechstein’s Bat:
Weight: 8.0 to 12.0 g ( 0.25 to 0.4 lbs)
Length: 4.5 to 5.5 cm ( 2.0 in)
Wingspan: n/a
Gestation period: 50 to 60 days
Number of young: 1
Life span: over 10 years
Diet: insects
Distinctive qualities: closely related to Mouse-eared bat but smaller, with very large ears; prefers open spaces and shelter in hollow trees; avoids attics, but will inhabit a cave; hibernates in quarries during winter, between rocks where wind and rain cannot disturb; leaves from hiding late at night and stays low to ground.

Species distinctions: Horeshoe bat:
Weight: 16.0 to 28.0 g ( 0.5 to 1.0 oz)
Length: n/a
Wingspan: 35.0 to 40.0 cm ( 14.0 to 16.0 in)
Gestation period: 60 to 75 days
Number of young: 1 or 2
Life span: 25 years
Diet: insects, beetles, moths
Distinctive qualities: horseshow-shaped leaf-nose; leave daytime resting places late in evening; make several trips then return to sleep the rest of the night; fly low to catch prey; sleep upside down in lofts, barns, and caves; hibernate in winter.

Weight: 18.0 to 45.0 g ( 0.67 to 1.5 oz)
Length: n/a
Wingspan: 40.0 to 45.0 cm ( 16.0 to 18.0 in)
Gestation period: 60 to 70 days
Number of young: 1
Life span: 20 years
Diet: insects
Distinctive qualities: one of the largest bats, found throughout Europe; live in colonies, usually in caves or outside buildings where it is quiet; will catch prey during the day, but peak time is during the evening; sensitive to cold; hibernate and do not awake until spring is well advanced; females group together to give birth to single young, where young bats are kept in a form of "nursery".

Weight: n/a
Length: 40.0 to 49.0 mm ( 1.6 to 2.0 in)
Wingspan: 20.0 cm ( 8.0 in)
Gestation period: n/a
Number of young: 1
Life span: n/a
Diet: n/a
Distinctive qualities: fur is neither grey nor brown but coloured, such as red or even "silver" (black, frosted with white tips); live in forest; more wool-like fur than other bats; will take shelter in hollow trees or weaverbird nests; sleep upside down among dried leaves to camouflage from danger; solitary, but will live in small groups (up to six) which cling together when asleep upside down.

Physics Application(s):

Echolocation: Bats are recognized as small, nocturnal mammals that are able to truly fly, not merely glide as the flying squirrel demonstrates, and form the second largest mammalian order, outnumbered only by the rodent order, which has more species. However, bats are also known specifically for their use of echolocation to navigate and catch prey in the darkness: they are constantly releasing ultrasonic waves during the whole time they are awake, using it to enhance their sight, which exceeds the sight of homo sapiens on its own. By emitting and receiving ultrasonic sound waves, they retain the ability to see further distances than many other organisms and can derive information which is much more refined. Although not all bats use echolocation, such as some megabats (large bats), many bats, many known as "microbats" do use sonar, however, the use versus no use suggests different ancestors.

Bat sonar may be expressed as a general process: ultrasonic waves are emitted from the bat as cries which then travel and are reflected back to the bat upon interacting with a moving or non-moving object of varied density. By measuring the delay in time from the wave emission and the return of the echo, the bat is able to determine the distance of the object, where amplitude is used as an indication of the size and shape of the object. With that information, the bat is able to locate precisely its prey with knowledge of how large or small it is, and thus it is able to hunt for its prey.

However, the process is not really as simple as explained, as there are other factors to be considered. The sound waves emitted may be of varying frequencies, varying by species and individual, and different sound waves used may collect more refined information: Eptesicus fuscus, the brown bat, uses sound waves classified as ‘broad-band FM", which are measured to be approximately 100.0 to 20.0 kHz, which allows for good echoes of distance, size, and shape. It has also been found that the production of ultrasonic cries demands from the bat a large amount of energy, particularly if the bat is flying, which would suggest that the hunt for food is an exhausting activity. However, it has been found that to bypass the affects of participating in the two activities at once, bats who use sonar inhale oxygen to use their flight muscles and exhale air pulses in order for the ultrasonic waves to be transmitted.

Another issue to consider is when the bat begins to move in a chase after its target: how does the echolocation function at that time? Through research, it has been found that bats possess a mechanism called automatic gain control (AGC), which provides the bat with the perception of a fixed echo intensity level as it approaches its target: where echoes will change based on the change in distance and echo strength, contractions of muscles in the bat’s middle ear diminishes after ultrasound emission, which produces changes in the bat’s hearing and balances the echo changes due to distance. Amplitude would also change as the bat moves, however, it is believed that the AGC regulates the amplitude as well.