Live animal radiography to measure developmental instability in populations of small mammals after a natural disaster

Stress placed on individuals in a population from natural and anthropogenic disturbances can elevate developmental instability. We studied the result of a natural disaster when one-third of a forested nature preserve was destroyed by an F3 tornado. Populations of two abundant species of small mammals, Peromyscus maniculatus and P. leucopus, were monitored in both disturbed and undisturbed habitats. We used an X-ray technique to measure developmental instability as indicated by fluctuating asymmetry (FA) in cranial and skeletal features of live animals. FA in femur length was higher in disturbed habitat for P. leucopus but was higher in undisturbed habitat for P. maniculatus. This difference in developmental instability mirrors differences in habitat preference between these species: P. leucopus prefers forest habitat and P. maniculatus prefers open, herbaceous habitat. These results were not explained by either food availability or body condition, both of which were higher in the disturbed habitat suggesting higher quality for this habitat. Thus, the FA response may be related to other indicators of habitat quality, e.g., vertical stratification, coarse-woody debris, or population density, which may differ between undisturbed and disturbed habitats.