Transcript Bats

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:


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.

Bats do a number of interesting
morphological things.
– Musculature differences.
– Forearm specialization.
– Modification of the shoulder.
– Hind limb rotation.
– Tricks w/ echolocation.
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

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.
Basic Bat Morphology:
Townsend’s big-eared bat.
Basic Bat Morphology:
Townsend’s big-eared bat.
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 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 “logdistance” vision. Bats use “short-distance”
hearing.
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 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.
Mechanics of Flight.
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 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 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 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










Family / species
Phylostomatidae
Macrotus waterhousii
Artibous jamaicansis
Choeronycteris mexicana
Vespertilionidae
Myotis yumanensis
M. evotis
M.lucifugus
Plecotus townsendii
Food
WL
AR
Insects / fruit
Fruit
Nectar
.112
.219
6.8
5.6
6.9
Insects
Insects
Insects
Insects
.084
.077
.099
.090
6.7
6.5
6.5
6.0
Some Examples

Family / species
Food
WL
AR

Molosidae
Tadaridae brasiliensis
T. molosa
Eumops parotis
Insects
Insects
Insects
.165
.159
.266
8.6
9.7
10.0
.112
.137
.283
.215
.181
4.6
4.9
5.7
8.6
7.5








Brown Creeper
Yellow Warbler
Brown Headed Cowbird
Chimney Swift
Cliff Swallow
Echolocation

True echolocation occurs only in the
microchiroptera.
– Sound is produced in the larynx.
– Sound is emitted through the nose or the
open mouth.
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.
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.
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.
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).
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.
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.
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.
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.
Chiropteran 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 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.
Icaronycteris and Myotis. Note
the scapula, radius & ulna, and
calcar.
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

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 microchiroptera, 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

Contrast the teeth of an insectivorous
vespertilionid (A & B), a nectivorous
phyllostomatid (C & D), and a
frugivorous phyllostomatid (E & F).

Pteropus,
Myotis, and
Molossus.

Anterior
and
posterios
views of
the
proximal
end of
humerus.

Note the
extensive
change
inposition
of the
head.
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.

Compare also the
flight engine of birds
and bats.
Flight engine

Consider also what happens in the
elbow.
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 ‘sacwinged’ 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

Also known as the
sheath-tailed bats.
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


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.
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




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





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.’
Rhinolophus: note the ‘horse
shoe’ and the sella.
Rhinolophid: Hipposideros sp.
Note the large nasal openings and
indented rostrum.
Rhinolophids

Note the sepcialized sternum of the
Rhinolophid compared to Myotis.
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


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.
Noctilio
leporinus:
note the
long rakelike feet.
Wingspan =
50cm.
They ‘fish’.
Phyllostomidae





49 genera and 141 species of newWorld 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

Other species make tents and are
insectivorous. Some tent-making forms
are polygynous.
Phylostomids
Compare the skulls of a fruit
eating Phylostomatid: Artibeus,
and a nectar feeder:
Choeronycteris mexicana.
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



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.
Natalus lepidus
Natalus lepidus
Note the fused lumbar vertebras
of Natalus stramineus.
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




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



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




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.
Eptesicus
fuscus
Lasiurus cinereas
Lasiurus cinereus: note the
shortened rostrum characteristic
of some insect feeding bats.
Myotis lucifugus
Myotis septentrionalis
X-ray
photograph of
Plecotus
townsendii in
flight.
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.
Compare the elbow of a
verspertilionid and a molossid.