Chiroptera

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Chiroptera Evolution of Flight
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Vertebrate Flight

• True flight is found in 3 vertebrate groups.
• Reptiles (Pterosaurs etc)
• Aves
• Mammalia
• Many vertebrate glider groups, including mammals,
  frogs, geckos, lizards, snakes, and fish.

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Questions to Ponder

• What selective pressures led to the evolution of
  flight in bats?
• How did bats take to the air?
• Top down hypothesis
• Bottom up hypothesis
• Where there intermediate forms?
• Why are bats nocturnal birds diurnal?

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Some Weirdness.

• Bats do a number of interesting morphological
  things.
• Musculature differences.
• Forearm specialization.
• Modification of the shoulder.
• Hind limb rotation.
• Tricks w/ echolocation.

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Another Question

• Why is there but 1 group of bats (maybe 2), but 4
  marsupial glider groups, 3-4 rodent glider
  groups, 1 dermopteran group, 1 amphibian glider
  group, and numerous reptilian glider groups?

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Basic Physical Requirements of Vertebrate Flight

• Need for a lifting surface
• each group evolved wings.
• Means of propulsion
• again, wings provide thrust.
• Control of stability
• wt. Concentrated near center of mass for
  metabolic efficiency
• decreased wt. of appendages
• increased appendage manageability
• Physiological and CNS changes.

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Basic Bat Morphology Townsends big-eared bat.
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Basic Bat Morphology Townsends big-eared bat.
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Modes of Flight

• Reptiles little flapping primarily gliding.
• Aves (all w/ varying degrees of maneuverability)
• rapid gliding
• slow gliding
• rapid flapping
• slow flapping

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Modes of Flight

• Bats
• low speed w/ extreme maneuverability.
• NOTE bats forage and eat on the wing, whereas
  flycatches land to eat. Also, bats echolocate
  whereas birds require log-distance vision.
  Bats use short-distance hearing.

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Mechanics of Flight

• Based on Bernoulli principle
• Air moving over top of wing moves faster than air
  on bottom.
• This creates negative pressure on top of wing.
• Leading edge is raised above Plane of Motion.
• Air is directed against ventral surface of wing.
• ? angle of attack.

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Mechanics of Flight.

• Camber is anteroposterior curvature.
• The greater the camber angle of attack, the
  more lift is produced
• If camber angle of attack is too great,
  turbulence results and you reach a stalling
  point.
• Drag is opposite to direction of movement.
• Depends on speed, surface area, and shape.
• Drag increases in proportion to wing surface
  area, as square of speed, with angle of attack
  and camber.

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Mechanics of Flight.
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Bat Wings.

• High camber
• High lift at low speeds.
• Excessive drag at high speeds.
• Camber angle of attack
• Held constant during wing beat cycle.
• Controlled by propatagium and plagiopatagium.
• Humerus and radius occipito-pollicalis control
  leading edge.

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Bat Wings.

• Camber angle of attack cont.
• Trailing edge controlled by hind foot and tensor
  plagiopatagii.
• Camber vie humerus and digit 5.
• Can be modified for extreme lift at low speed.
• Thrust
• Thrust during cycle because of give of trailing
  edge of chiropatium while leading edge is rigid.

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Bat Wings.

• Aspect ratio.
• Length / width or
• (wing span)2 / wing area.
• Low aspect ratio wings are good for low speed and
  maneuverability.
• High aspect ratio wings are good for rapid flight
  and endurance.

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Bat Wings.

• Wing loading (wt / wing area).
• Reduced wing loading results in greater ability
  to fly at low speed.
• High wing loading is associated with ability to
  achieve high speed.

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Some Examples

• Family / species Food WL AR
• Phylostomatidae
• Macrotus waterhousii Insects / fruit .112 6.8
• Artibous jamaicansis Fruit .219 5.6
• Choeronycteris mexicana Nectar 6.9
• Vespertilionidae
• Myotis yumanensis Insects .084 6.7
• M. evotis Insects .077 6.5
• M.lucifugus Insects .099 6.5
• Plecotus townsendii Insects .090 6.0

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Some Examples

• Family / species Food WL AR
• Molosidae
• Tadaridae brasiliensis Insects .165 8.6
• T. molosa Insects .159 9.7
• Eumops parotis Insects .266 10.0
• Brown Creeper .112 4.6
• Yellow Warbler .137 4.9
• Brown Headed Cowbird .283 5.7
• Chimney Swift .215 8.6
• Cliff Swallow .181 7.5

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Echolocation

• True echolocation occurs only in the
  microchiroptera.
• Sound is produced in the larynx.
• Sound is emitted through the nose or the open
  mouth.

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Echolocation

• Sound quality.
• Some bats produce high intensity pulses.
• Used primarily by insectivores and piscivores.
• Molossids
• Noctilionids
• Vespertilionids
• Some HIP bats emit the pulses through the nose.
• Rhinolophids.

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Echolocation

• Some bats produce Low Intensity Pulses.
• These bats are called whispering bats. They feed
  primarily on fruits, nectar, and some small
  vertebrates.
• Why use high frequency sounds?
• High frequency sounds attenuate rapidly in air.
• Higher frequencies are associated with shorter
  wavelengths.

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Echolocation

• Why use high frequency sounds?
• Shorter wavelengths are more efficient at
  detecting small insect sized prey.
• High frequency sound may be distrinct from
  background noise.

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Echolocation

• Sound Force.
• A dyne is defined as the force required to
  accelerate a 1g mass to 1 cm/s/s.
• Humans have a lower force threshold of about
  .0002 dynes.
• Bats are capable of producing sound with forces
  ranging from 1 dyne to 200 dynes (equivalent to a
  top fuel dragster).

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Echolocation

• Morphological specialization
• Tensor tympani and stapedius are extremely well
  developed. Also, these muscles receive action
  potentials shortly after (3 milliseconds) sound
  action potentials are produced.
• Changes in neural pathways.
• Ability to beam sound through nose leafs and
  lips.

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Echolocation

• Tragus and antitragus used to detect sounds.
• Bones housing the inner ear and middle ear are
  insulated from the rest of the skull by fat and
  blood filled sinuses.

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Echolocation

• Echolocation signals.
• FM signals
• These signals have a short duration, but sweep a
  broad frequency range.
• FM signals are ideally suited to determining
  size, shape, surface qualities, and range of a
  target.

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Echolocation

• CF signals
• CF signals are constant frequency (or nearly so)
  but have a significant time duration.
• CF signals are good for detecting presence, and
  through dopler shift, whether prey is approaching
  or departing.

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Chiropteran Diversity
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Bat Diversity

• Earliest bat fossils are from the early Eocene of
  North America
• Icaronycteris index
• There are no intermediate forms - earliest bats
  are good bats.
• Underived characters include 38 teeth (compared
  to 44 for underived eutherian number).

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Bat Diversity

• Icaronycteris was capable of flight and
  echolocation, but lacked a keeled sternum.
• Icaronyceris had only partial fusion of the
  radius and ulna, and dorsal position of the
  scapula.
• Earliest megachiroptera are from the early
  Oligocene of Europe and Africa
• Archaeopteropus and Propotto.

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Icaronycteris and Myotis. Note the scapula,
radius ulna, and calcar.
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Bat Diversity

• As is often the case in biology, there has been a
  rather ugly controversy concerning the
  evolutionary history of the megachiroptera and
  microchiroptera. Are they diphyletic or
  monophyletic?

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Megachiroptera

• Pteropodidae
• 36 genera and 154 species of tropical and
  subtropical Old World fruit and nectar feeding
  bats. Predominantly nocturnal, with body sizes
  ranging from 15g to 1.6Kg.
• They do not echolocate like micro-chiroptera,
  they are specialized for feeding on fruit and
  nectar (note teeth and palates they do not
  consume pulp), and they have odd eye structures.

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Teeth Diet

• Contrast the teeth of an insectivorous
  vespertilionid (A B), a nectivorous
  phyllostomatid (C D), and a frugivorous
  phyllostomatid (E F).

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• Pteropus, Myotis, and Molossus.
• Anterior and posterios views of the proximal end
  of humerus.
• Note the extensive change inposition of the head.

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Flight engine

• Think about the forces involved in the wing-beat
  cycle, and why the humeri of megachiroptera and
  microchiroptera might differ.
• Molossid shoulder is shown on next slide.

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• Compare also the flight engine of birds and bats.

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Flight engine

• Consider also what happens in the elbow.

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Microchiroptera

• Rhinopomatidae
• Mouse-tailed bats.
• Considered most primitive because of presence of
  2 phalanges on second digit of manus, and unfused
  premax.

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Emballonuridae

• 13 genera and 47 species of sac-winged bats
  distributed worldwide.
• They are insectivorous w/ dilambdodont teeth
  (30-34).

• Sacs are ventral within the propatagium of males
  (less so in females), and are probably used for
  production of pheromones

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Emballonuridae

• Also known as the sheath-tailed bats.

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Craseonycteridae

• Known only from Thailand. The family is
  monotypic. Craseonycteris thonglongyai weighs
  only 1.5 - 2.0g.
• Also known as the bumblebee bat.
• They have no external tail or calcar.

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Nycteridae

• 1 genus and 12 species of slit-faced bats in
  sub-Saharan Africa, Madagascar, Sumatra, Borneo,
  and Malaysia, Java, Bali, and Kangean.
• Have a groove through the face, which together
  with the nose leaf, functions in propagation of
  low intensity echolocation calls.

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Nycteridae

• Uropatagium encloses tail, and end of tail is
  shaped like a T.
• Mose are insectivorous, but some feed on
  vertebrates, including other bats.

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Megadermatidae

• False-vampire bats of Australia, Africa, india,
  the East Indies, and southeast Asia.
• They have large ears which are united across the
  forehead, a divided tragus, nose leaf, and
  absence of upper incisors.
• Some have wingspans up to 1m.
• Some feed on lizards, others on arthropods and
  insects.

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Rhinolophidae

• Horseshoe bats Karl Koopman says there are 10
  genera and 130 species.
• They include the old world leaf-nosed bats.
• There may be 2 subfamilies Rhinolophinae and
  Hipposiderinae.
• Hipposiderinae lack the sella, and have fewer
  teeth.
• Hibernating forms have delayed fertilization.

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Rhinolophus note the horse shoe and the sella.
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Rhinolophid Hipposideros sp. Note the large
nasal openings and indented rostrum.
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Rhinolophids

• Note the sepcialized sternum of the Rhinolophid
  compared to Myotis.

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Mormoopidae

• This is the group established by James Dale
  Shitty Smitty Smith.
• They are New World, all have a tail and a tragus
  with a secondary fold of skin.
• They lack a nose-leaf and have small eyes.

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Noctilionidae

• These are the buldog or fishing bats. There is
  but 1 genus and 2 species.
• Larger species feeds on fish, the smaller species
  feeds on insects.

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Noctilio leporinus note the long rake-like feet.
Wingspan 50cm. They fish.
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Phyllostomidae

• 49 genera and 141 species of new-World leaf nosed
  bats.
• Some species (including frugivores and
  sanguinivores) lack the nose leaf.
• 3 species of vampires - feed either on cattle or
  birds.
• Vampires exhibit food sharing this is reciprical
  altruism.
• Consider the physiological implication of feeding
  on blood.

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Phyllostomids

• Other species make tents and are insectivorous.
  Some tent-making forms are polygynous.

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Phylostomids
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Compare the skulls of a fruit eating
Phylostomatid Artibeus, and a nectar feeder
Choeronycteris mexicana.
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Mystacinidae

• These are the short-tailed bats from New Zealand,
  one of which is extinct since the 60s.
• They are good on the ground, and like vampires,
  can take off from the ground.
• Note the talon.
• They can furl the patagia, and are capable of
  burrowing.

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Natalidae

• 1 genus and 5 species of funnel-eared bats from
  Mexico to the South America and the Caribean.
• Domed fore-head and no nose leaf.
• Males have a natalid organ (glandular sensory
  cells) below skin on forehead.

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Natalus lepidus
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Natalus lepidus
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Note the fused lumbar vertebras of Natalus
stramineus.
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Furipteridae

• 2 genera and 2 species of smoky bats.
• Costa Rica to Chile.
• The thumb is very small and completely enclosed
  by the wing.

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Thyropteridae

• Only 2 species of disc-winged bats.
• Distributed from Mexico to Brazil
• Thumb discs are attached by a pedicle, and appear
  to aid the animals while clinging to fronds of
  banana leaves etc.
• Thyroptera tricolor on next slide.

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Myzopodidae

• Old-world sucker-footed bat. Monotypic family
  contains only Myzopoda aurita.
• Only bat species endemic to Madagascar.
• Disc does not have a pedicle, and represents an
  independent origin of the structure.

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Vespretilionidae

• Evening bats most diverse family of bats, and
  with the exception of murid rodents, the most
  diverse mammalian family.
• Worldwide distribution.
• Predominantly insectivorous.
• Hibernate in the winter, but arouse to drink.

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Eptesicus fuscus
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Lasiurus cinereas
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Lasiurus cinereus note the shortened rostrum
characteristic of some insect feeding bats.
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Myotis lucifugus
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Myotis septentrionalis
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X-ray photograph of Plecotus townsendii in flight.
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Molossidae

• 12 genera and 80 species of free-tailed bats.
• Found in both the old and new worlds.
• Molossids do not hibernate - Tadarida
  brasiliensis migrates and does go into torpor.
• Military attempted to use bat-bombs during WWII.

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Compare the elbow of a verspertilionid and a
molossid.
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