Facial musculature was examined in the Florida manatee, Tricbecbus manatus latirostris, in order to develop a functional model of perioral bristle use. Muscles identified include the M. levator nasolabialis, M. buccinatorius, M. maxillonasolabialis, M. centralis nasi, M. lateralis nasi, M. spbincter colli profundus pars oris, M. orbicularis oris, M. mandibularis, and M. mentalis. A new muscle, M. centralis nasi, has been named and is an integral part of perioral bristle movement. The snout of the Florida manatee is capable of performing complex movements. The prehensile ability of Florida manatees can be explained in the context of a muscular hydrostat as defined by Kier and Smith (1985). Eversion of certain bristles in the upper lip occurs by shortening longitudinal, transverse, and semicircular muscles in combination with volume displacement due to compensatory changes in the shape of the snout. Midline sweeping of these bristles is accomplished by the contraction of M. centralis nasi. Eversion of bristles on the lower jaw is a result of shortening of M. mentalis. Contraction of M. orbicularis oris pushes vegetation into the oral cavity. All observed movement patterns and uses of perioral bristles can be explained by variation of these sequences within the context of muscular hydrostat function.

This study examined 32 children’s (M age=1;8 years) engagement in joint attention (JA) and the relation between JA and vocabulary size across mother–child (MC) and mother–child–sibling (MCS) contexts. In the MCS context, mothers engaged in JA more with one child than both children; they engaged in less JA with target child than they did in the MC context. JA style was generally unrelated across the contexts. Coordinated JA and children’s vocabulary were significantly related only for the MCS context. Findings suggest the number of social partners influences JA dynamics and multi-child contexts can be positive language learning environments.

Close human-wildlife interactions are rapidly growing, particularly due to wildlife tourism popularity. Using both laboratory and ecological observation studies we explored potential interspecies communication signalling mechanisms underpinning human-animal approach behaviour, which to date have been unclear. First impression ratings (n = 227) of Barbary macaques' social and health traits were related to the macaques' facial morphology and their observed behaviour supporting a shared facial signalling system in primates. These ratings significantly predicted intended approach to the macaques during hypothetical interactions. Finally, real-world interspecies proximity was observed and found to be best predicted by the interaction between human first impression perception and animal behaviour. Specifically, perceived macaque health in interaction with actual macaque dominance drives close interactions despite human proclivity to avoid dominant animals, raising safety concerns in interspecies interactions.A growing body of evidence suggests that we automatically form first impressions of people from their faces. These first impressions are made quickly 1 , non-consciously 2 , and incidentally without instruction 3 . These first impression judgements have been shown to influence people's behaviour toward an individual, determining the initiation of positive or negative interactions 4 . For instance, dominance is considered to be a cue of a person's intentions, and a dominant person could be considered as a potential threat 5 . Although the accuracy of first impression judgements has been largely debated 5-7 , previous studies have shown that first impressions of survival-related traits, e.g. dominance, were more accurate and consistent than more subtle characteristics such as intelligence, suggesting a potential evolutionary advantage of accurate first impression judgements. First impressions are important in interactions as they allow for the prediction of future behaviour 8 , which, if these judgements are inaccurate, could lead humans to put themselves at risk. However, to date, little is known about how humans make judgements of whether and how to interact with individual non-human animals (hereafter animals), and whether these judgements are accurate.It has been suggested that humans and non-human primates (hereafter primates) have a shared personality facial signalling system, and that both species could use first impression judgements to accurately assess other primate species' social and health traits 9 . For example, naïve participants have been shown to accurately rate extraversion social traits such as dominance in chimpanzees (Pan troglodytes) from static, neutral faces when compared to personality ratings from the chimpanzees' keepers 9,10 . Japanese and rhesus macaques (Macaca fuscata & Macaca mulatta) have also been shown to have a visual attentional preference for 'trustworthy' human faces 11 . Indeed, morphometric measures of facial structure such as the facial width to height ratio (fWHR) has been e...