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Origin of flight in birds and bats



From: Ben Creisler
bh480@scn.org

A couple of recent items that apparently have not been mentioned on the
DML: 

Flapping robot gives insights into flight
http://www.sciencedaily.com/releases/2011/10/111017214919.htm

K. Peterson, P. Birkmeyer, R. Dudley and R. S. Fearing (2011)
A wing-assisted running robot and implications for avian flight evolution. 
Bioinspiration & Biomimetics 6(4): 
doi:10.1088/1748-3182/6/4/046008
http://iopscience.iop.org/1748-3190/6/4/046008/

Abstract 
DASH+Wings is a small hexapedal winged robot that uses flapping wings to
increase its locomotion capabilities. To examine the effects of flapping
wings, multiple experimental controls for the same locomotor platform are
provided by wing removal, by the use of inertially similar lateral spars,
and by passive rather than actively flapping wings. We used accelerometers
and high-speed cameras to measure the performance of this hybrid robot in
both horizontal running and while ascending inclines. To examine
consequences of wing flapping for aerial performance, we measured lift and
drag forces on the robot at constant airspeeds and body orientations in a
wind tunnel; we also determined equilibrium glide performance in free
flight. The addition of flapping wings increased the maximum horizontal
running speed from 0.68 to 1.29 m s−1, and also increased the maximum
incline angle of ascent from 5.6° to 16.9°. Free flight measurements show a
decrease of 10.3° in equilibrium glide slope between the flapping and
gliding robot. In air, flapping improved the mean lift:drag ratio of the
robot compared to gliding at all measured body orientations and airspeeds.
Low-amplitude wing flapping thus provides advantages in both cursorial and
aerial locomotion. We note that current support for the diverse theories of
avian flight origins derive from limited fossil evidence, the adult
behavior of extant flying birds, and developmental stages of already volant
taxa. By contrast, addition of wings to a cursorial robot allows direct
evaluation of the consequences of wing flapping for locomotor performance
in both running and flying.
===

Origin of flight in bats

http://www.nature.com/news/ancient-bats-got-in-a-flap-over-food-1.9304

SVP Abstracts 2011

PADIAN, Kevin, University of California, Berkeley, CA, USA; DIAL, Kenneth,
University of Montana, Missoula, MT, USA 

PHYLOGENETIC DISTRIBUTION OF ECOLOGICAL TRAITS IN THE ORIGIN AND EARLY
EVOLUTION OF BATS

Living bats differ from other flying vertebrates (birds and pterosaurs) in
having poor sight, echolocating, stressing slow, maneuverable fight, and
seldom gliding. It has generally been assumed that gliding is a necessary
precursor to fight, but phylogenetic analyses show that no gliding forms
are found among the closest relatives of flying forms, and many gliding
lineages have evolved with no apparent tendencies to powered fight. The
most basal known bats could fly, but the most basal Onychonycteris lacked
bony specializations for echolocation, which has suggested that flight
evolved frst. However, other mammals such as the tenrec do not fly but can
echolocate in a more rudimentary way, and they lack chiropteran bony
specializations for this. Nocturnal animals generally evolve enhanced
vision, but animals that live in almost total darkness (e.g., caves) tend
to reduce sight. Cave insects also tend to lose flight capacity. The visual
capabilities of the earliest bats are ambiguous, but nearly all living bats
are crepuscular, roosting in dark places.  
We mapped traits related to echolocation, locomotion, vision, diet, and
habitat in crown and stem bats. Results suggest that echolocation may be an
?evolvable,? modular trait that has been hard-wired to various degrees in
mammals. Basal bats are inferred to have been insectivorous, but they may
have hunted differently than living bats do. Phylogenetic mapping shows
that neither the ability to fly well nor to echolocate well may have been
basal to bats; living in caves and feeding on poorly mobile insects may
have been basal habits at least for crown-group bats. No outgroups to bats
are or apparently were bipedal; thus the forelimbs of bats could only be
freed to evolve powered fight if they were no longer necessary to standard
quadrupedal locomotion. All bats can climb quadrupedally and this seems
basal for crown-group bats. Caves have fewer predators than trees, and the
ability to suspend the body from the roofs of caves appears to have been
possible for all known Chiroptera, living and extinct. The features of cave
habitats, although poorly fossilized, may explain much about the origin of
bats.



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