Kristin Bishop
Ph.D., graduated in 2006
Now a post-doc at University of California, Davis (kvwbishop@ucdavis.edu)
My primary research interest is in the evolution of novel locomotor modes and associated morphological and behavioral shifts that accompany it. Understanding the evolution of powered flight in bats from an arboreal gliding ancestor is a particular challenge because gliding and powered flight appear to have very different morphological adaptations associated with them, suggesting that they have disparate optimization criteria. Because of differences in the mechanics of gliding and flapping flight, some workers have suggested that such a transition is mechanically impossible and that bats must have acquired flight in some other way. Others predict that small increments toward flapping behavior in a glider confer an aerodynamic benefit and that the gliding to flapping transition is the only plausible evolutionary scenario in bats.
Before we can meaningfully address whether a gliding to flapping transition is mechanically plausible in the bat lineage, it is necessary to better understand the mechanics of gliding in living mammalian gliders. In order to do this I combine kinematic analysis of gliding mammals with studies of physical models of flexible, extensible wing membranes to better understand how the wings of gliding mammals produce the aerodynamic forces necessary for gliding flight.
Gliding has evolved separately in at least six living mammal groups: the Dermopterans, or flying lemurs; 2 groups of rodents, the Anomalurids, or scaly tailed flying squirrels, and within the Sciuridae, the squirrel family; and 3 marsupial lineages, the Acrobatids, and two possum genera, Petaurus and Petauroides. All of these independent acquisitions of gliding have resulted in very similar morphologies, suggesting there may be some mechanical constraints that represent general rules for mammalian gliders. If so, and if bats evolved from a gliding mammal, then we can use features that are common to all gliding mammals to reconstruct some of the characteristics of preflight bat ancestors.
Most of what we know about aerodynamics comes from human engineered aircraft. It is not known to what extent we can apply standard aerodynamic theory directly to more animal-like wings, which are flexible, stretchy and can be moved. To better understand how flexible, extensible wings generate aerodynamic forces, I am conducting wind tunnel tests on simplified physical models of wings that resemble glider wings in shape and size and measuring the aerodynamic forces they generate compared to similarly shaped rigid wings.
The relationship between 3-D kinematics and gliding performance in the southern flying squirrel, Glaucomys volans (pdf)
Journal of Experimental Biology , 209 (4): 689-701 (2006)
Bishop, KL
Bat flight aerodynamics: new insights from
three-dimensional kinematic analysis
In Functional and Evolutionary Ecology of Bats (2006)
Ed. T.H. Kunz, Z. Akbar and G.F.
McCracken, pp. , Oxford University Press.
Swartz, S.M., Bishop, K.L., and Ismael-Aguirre, M.F.
