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Chiroptera & Evolution of Flight. 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. Questions to Ponder:.

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vertebrate flight
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.
questions to ponder
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?
some weirdness
Some Weirdness.
  • Bats do a number of interesting morphological things.
    • Musculature differences.
    • Forearm specialization.
    • Modification of the shoulder.
    • Hind limb rotation.
    • Tricks w/ echolocation.
another question
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?
basic physical requirements of vertebrate flight
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.
modes of flight
Modes of Flight
  • Reptiles: little flapping & primarily gliding.
  • Aves (all w/ varying degrees of maneuverability)
    • rapid gliding
    • slow gliding
    • rapid flapping
    • slow flapping
modes of flight11
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.
mechanics of flight
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.
mechanics of flight13
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.
bat wings
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.
bat wings17
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.
bat wings18
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.
bat wings20
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.
some examples
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
some examples23
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
echolocation
Echolocation
  • True echolocation occurs only in the microchiroptera.
    • Sound is produced in the larynx.
    • Sound is emitted through the nose or the open mouth.
echolocation25
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.
echolocation26
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.
echolocation27
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.
echolocation28
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).
echolocation29
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.
echolocation31
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.
echolocation32
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.
echolocation33
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.
bat diversity
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).
bat diversity39
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.
bat diversity42
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?
megachiroptera
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.
teeth diet
Teeth & Diet
  • Contrast the teeth of an insectivorous vespertilionid (A & B), a nectivorous phyllostomatid (C & D), and a frugivorous phyllostomatid (E & F).
slide49
Pteropus, Myotis, and Molossus.
  • Anterior and posterios views of the proximal end of humerus.
  • Note the extensive change inposition of the head.
flight engine
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.
flight engine53
Flight engine
  • Consider also what happens in the elbow.
microchiroptera
Microchiroptera
  • Rhinopomatidae
    • Mouse-tailed bats.
    • Considered most primitive because of presence of 2 phalanges on second digit of manus, and unfused premax.
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

Emballonuridae
emballonuridae58
Emballonuridae
  • Also known as the sheath-tailed bats.
craseonycteridae
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.
nycteridae
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.
nycteridae61
Nycteridae
  • Uropatagium encloses tail, and end of tail is shaped like a ‘T’.
  • Mose are insectivorous, but some feed on vertebrates, including other bats.
megadermatidae
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.
rhinolophidae
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.’
rhinolophids
Rhinolophids
  • Note the sepcialized sternum of the Rhinolophid compared to Myotis.
mormoopidae
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.
noctilionidae
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.
phyllostomidae
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.
phyllostomids
Phyllostomids
  • Other species make tents and are insectivorous. Some tent-making forms are polygynous.
slide80
Compare the skulls of a fruit eating Phylostomatid: Artibeus, and a nectar feeder: Choeronycteris mexicana.
mystacinidae
Mystacinidae
  • These are the short-tailed bats from New Zealand, one of which is extinct since the 60’s.
  • 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.
natalidae
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.
furipteridae
Furipteridae
  • 2 genera and 2 species of ‘smoky bats.’
  • Costa Rica to Chile.
  • The thumb is very small and completely enclosed by the wing.
thyropteridae
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.
myzopodidae
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.
vespretilionidae
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.
molossidae
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.