# Fluctuating Asymmetry and Stress in _Macaca fuscata_: Does Captivity Affect Morphology?
## 4 Discussion  
Fluctuating asymmetry has been used in recent and past literature as a way of measuring the morphological fitness and wellbeing of an individual, a group or a population in relation to the environment in which they live [5; 18; 45; 46]. This article analyses the differences in magnitude and patterns of FA in the mandible of wild and captive _Macaca fuscata_ to address the potential impact of captivity stressors on primate skeletal morphology. Our hypothesis holds that the captive macaques show a significantly higher degree of FA than the wild group due to the stress of an enclosed environment (with all its limitations regarding diet, mobility, etc.). Conflicting results and differences in the methodologies used in previous studies have led to uncertainty about the efficacy and consistency of FA in registering developmental instability [32]. In this paper, we used a combination of methods to address the presence and impact of FA on the morphology of captive individuals, thus overcoming the ambiguities of previous literature. Our results indicate that the mandibles of captive and wild \(M\). _fuscata_ show distinct morphologies, as do the mandibles of male and female individuals. Such differences are significant for the overall morphology (Table 5) and the symmetric component (Table 3). The shape differences associated with sex and group (captive/wild) seem independent. If captivity does affect mandibular shape, it appears that the impact is not differential between females and males, whose mandibles vary independently from captivity. The anterior region of the mandible and the rami appear to be the major source of morphological variation in the symmetric component (Figure 3). These findings confirm the results observed by [33] about a morphological difference in the mandible of captive and wild \(M\). _fuscata_. The most direct interpretation of our findings would be that the captive conditions could influence the overall shape of the macaque mandible. Nevertheless, caution must be applied because several potentially relevant factors were not tested in this work. For example, a dissimilar age composition in the wild and captive samples may drive the observed differences. We tried to limit the effect of age by only including individuals with fully erupted third molar. Asymmetry in the positioning of mandibular comdyles and in the orientation of the goni region was highlighted by the PCA of the asymmetric shape (Figure 5). The presence of fluctuating, instead of directional, asymmetry was suggested by the distribution of the PC scores (Figure 6) along the first two principal components of the asymmetric shape, and demonstrated by the decomposition of total asymmetry (99.97% of total variance was attributable to FA). However, no significant difference in asymmetry (fluctuating or directional) was found between the captive and wild \(M\). _fuscata_, regardless of the approach used [35; 39]. The non-significant association between asymmetry, group (captive/wild) and sex (Table 4), and the non-significant impact of FA on the overall morphology (Table 5), suggest that FA is of negligible magnitude in the sample analysed. Based on the findings above, three interpretations can be put forward:  
1. The stress associated with the captive conditions of the individuals analysed was not strong enough to trigger a change in FA. In this case, captivity may not impose sufficient environmental stress to trigger a response in the asymmetry pattern of the mandible. * FA is not a good indicator to detect environmental stress, at least in the conditions and for the species analysed. * The mandible is not an ideal region to identify developmental stress using FA. The shape differences observed here between captive and wild _M.fuscata_ (when overall shape and the symmetric components are analysed) suggest that captivity has exerted pressures on development.