Wing Morphology and Flight Performance in Rousettus Leschenaulti

1. Wing Morphology and Flight Performance in Rousettus Leschenaulti Elangovan, V., et al. “Wing Morphology and Flight Performance in Rousettus Leschenaulti.” Journal of Mammalogy Vol. 85 Issue 4 (2004): 806-813.

2. Taxonomy: • Kingdom: Animalia • Phylum: Chordata • Subphylum: Vertebrata • Class: Mammalia • Order: Chiroptera • Family: Pteropodidae (old world fruit bats) • Genus: Rousettus • Species: Rousettus Leschenaulti • Common Name: Leschenault’s Rousette

3. Background Information • India is currently the home to approximately 100 species of bats, including 12 fruit bats • The information gathered on these species is considerably limited due to the lack of field studies • Flight behavior is affected by both the structure and the shape their wings • Foraging distances are affected along with energy costs • Flight proficiency is also affected by changes in body mass • A body mass increase results in: • Flight speed decrease • Increased energy costs

4. Females nurse their young for 75 days before they are capable of flying and providing food for themselves ~ Bones tend to be light and slender ~ Each wing is supported by bones of arm and one finger ~ A bat’s patagium (wing membrane) is supported by arm and 4 elongated fingers - This patagium extends down behind hind legs & tail (aids in capturing prey when in flight)

5. Hypothesis • If the morphology of the bats’ wings are varied from others, then their flight performance will also be varied • After viewing data previously studied, this study focused on the behaviors of these bats at various stages of flight development compared to their wing growth pattern

6. Methods & Materials • 9 pregnant females were collected from India and each newborn was then used in the study • Every two days, the behaviors of the young bats were recorded • From day 5 through day 150 (@ 5 day intervals) measurements were taken of: • Body mass • Wingspan • Wing area For each bat, wingspan was measured by: -tracing outline onto a black sheet where bat was placed on its back

7. Measurement Calculations: -Wingspan: 2(distance from body axis to wing tip) -Wing aspect ratio: (wingspan)2/wing area -Body mass: nearest 0.1g on spring balance • When the bats reached between the ages of 20-75 days, flight tests were administered at 5 day intervals • Cushions were placed on the floor during each test incase a young bat fell accidentally • Each bat was given the opportunity to fly 3 times during each test (where the distance traveled was measured) and the best performance was recorded • Flight abilities categorized as: • “Flop” – stage 1 • “Flutter” – stage 2 • “Flap” – stage 3 • “Fly” – stage 4

8. Results & Discussion • Of the nine young originally collected for the study, 3 died as neonates and 1 died at 9 days of age • Leaving 5 for the remainder of the study Significant Days in Study: • - 30: 1st attempt of flight • 35: Fell vertically onto cushioned floor with flight distance of • approx. 8.8 cm. (not even into “flop” stage yet) • 40: Same as day 35 but flight distance now of approx. 32.5 cm. • 45: “Fluttered” to distance of approx. 295 cm. (stage 2) • 50: Flew fairly well to a distance of 883 cm. where it then landed • 55: Made few circles when in flight • 60: Reached flight capabilities similar to that of the adults

9. Growth of wingspan of R. Leschenaulti throughout length of study

10. 3 growth models were used to help explain the data collected • Logistic equation model  wingspan best shown using this • Gompertz model  wing area best depicted using this • Bertalanffy model • It was found that in young R. Leschenaulti bats, the wing membranes are developed well enough to sustain flight at about 6 weeks of age • Also, there was rapid growth of the hand region on the wings when the bats reached the capability of flight which is necessary to produce a thrust during the downstroke • Note that flexion of wings do not have full range of motion until they achieve longer arm lengths and larger wingspans

11. Logistic model  Directly correlated to wing area (below) Gompertz model 

12. It was found that the flight muscles are also not well developed at birth because there is no requirement for them until flight is achieved • At the later stages in development (anywhere after day 50), the flight speed and mechanical power both increase due to the increase and morphology of the wings • Allowing these bats to carry out a more skilled flight performance with greater agility • It was also observed that the young bats who chose to follow their mothers out on their first foraging flight received earlier exercise than those that chose not to • Which possibly lead to slight variation in wing parameters among the young bats

13. Main Points to Take From This Study This particular species is more advanced in the rate of development than others • Young R. Leschenaulti bats can begin to fly when they reach 45% of their body mass and about 77% of adult skeletal size • Note that in other species, bats normally begin flight when they reach 70% of body mass and nearly 95% of adult skeleton size More studies are necessary to compare this species to a more broad category of Chiroptera (bats)