Fluctuating Asymmetry and Stress in Macaca fuscata: Does Captivity Affect Morphology?

Fluctuating Asymmetry (FA) in morphology is used as a proxy for developmental instability in response to stress factors. FA has important implications for understanding the impact of differential environments and stressors on the skeletal phenotype. Here, we explore FA in the mandibular morphology of wild and captive Macaca fuscata to detect differences induced by the captive environment. We use two different approaches in Geometric Morphometrics to characterise the degree and patterns of FA and Directional Asymmetry (DA) based on 3D mandibular landmarks. Our results show that the wild and captive groups exhibit morphological dissimilarities in the symmetric component of shape while no significant degree of asymmetry (fluctuating or directional) was detected. Based on our results and on previous literature on the subject, we suggest that (I) captivity is likely to affect the mandibular morphology of M. fuscata; (II) FA may not be a suitable indicator to detect stress in the conditions analysed; and that (III) the mandible may not be the ideal region to study asymmetry because of its functional nature.