An aerodynamic perspective on hurricane-induced selection on Anolis lizards

Studies have demonstrated that hurricanes can drive selection in Neotropical anoles. In a recent study it was shown that post-hurricane survivors showed increased toepad areas, and surprisingly, shorter femurs.
One potential explanation for the reduction in femur length is that increased drag on individuals with longer femurs causes them to be blown off their perch. Consequently, lizards with shorter femora might survive better in hurricanes.
To gain insight into the form-function relationships of drag-reduction in perched lizards exposed to high-velocity winds, we quantified drag forces on Anolis lizard models in realistic grasping positions using computational fluid dynamics.
We showed that overall drag, as well as the relatively high drag at the hind limbs strongly increases with the distance of the pelvic region from the perch. As optimal postures to resist sustained arboreal pulling involve extended limbs, longer hind limbs increase the chance of having the limbs and pelvic region positioned outside the zone in which efficient shielding from the wind by the perch occurs.
Our study underlines the complexity of performance trade-offs on the evolution of limb morphology in arboreal lizards, and emphasizes the importance of generally ignored functions such as aerodynamic drag reduction in arboreal ecosystems. 

Methods

Case (.cas) and corresponding Data (-2000.dat) files from all simulations reported in the Results section of the article (Ansys Fluent version 19.1; also accessible with Ansys CFD Post). The five positions and inflow angle (0 or 20 degrees) are explained in Fig. 1a and Table 1.
The original .stl (triangular surface mesh) file from laser scanning of an Anolis carolinensis individual is provided as well.
The .out file gives time-dependent drag forces (N) for one posture (posture 1) from a transient simulation with a time-step size of 0.2 ms that was ran for 1000 time steps.