1. Flight in bats Wings Aerodynamics Evolution Adaptations for flight
Powered flight
Energetic cost of flight
Wing shape and foraging ecology

2. Discussion readings

3. Hypothetical evolution of a bat wing
Colugo
Bat

4. Flying lemur (colugo)

5. Current phylogeny
Teeling et al. PNAS 2001

6. Wing evolution Powered flight has evolved 3 times in vertebrates.
Bats have much greater control over wing shape and curvature than birds or pterosaurs

7. Aerofoil and lift
lift
Convex curvature of aerofoil causes air to pass faster over than under the wing.
This creates negative pressure above the wing, causing the wing to lift.
Greater angle of attack permits greater lift at low speed, until a stall.

8. Bat wing is an aerofoil

9. Digits prevent turbulence
Greater camber causes turbulence
Turbulence erodes lift, causes drag
Digits reduce turbulence and drag

10. Bats can manipulate camber
Adjusting angle of propatagium and membrane alters camber
which can increase lift and greatly increase maneuverability

11. Bat wing properties

12. Wing extension mechanism
Triceps connects to scapula and carpi radialis connects to humerus. Consequently, when suprapinatus contracts, arm and fingers automatically extend. Only shoulder muscles need to be large.

13. Wing pivot differs in birds and bats
Bats: clavicle pivots on sternum, while scapula is pulled up and down. Allows for equal power on up and down strokes.
Birds: humerus pivots on scapula. Most power is in downstroke.

14. Downstroke
Upstroke

15. Vampire bat wing motion

16. Bat flight aerodynamics
L = lift
D = drag
V = velocity
R = aerodyamic power

17. Wing flapping creates vortices

18. Wing flapping and flight power
At a flight speed of 2.35 m/s, Plecotus auritus
generates thrust mainly on the upstroke.

19. Wing flapping in horizontal flight of Rhinolophus ferrumequinum
Thrust is generated on upstroke only at low speeds.

20. Hovering flight
Glossophaga soricina hovering

21. Vampire bat jumping

22. Optimal flight speed
Hovering is costly, as is
high speed flight.

23. Physiological adaptations for flight
Bats flap their wings 10 times per second
Most bats take a breath on every wing beat
Exhalation occurs late in the upstroke. Echolocation coincides with wing beats, except during attack.
Heart rate increases 2-6 times resting rate during flight
Metabolic rate (oxygen consumption) during flight is about 14 times resting rate

24. Flight is more expensive than running in birds and bats

25. Bats differ in wing shape
Wing loading = mass/wing area
Aspect ratio = wingspan2/wing area
Low AR =
short, broad wings
High AR =
long, narrow wings

26. Wing shape and flight style

27. Call design fits foraging strategy