22 UKRI-SBE: Primate natal coats: Form and function

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The color of infants in many primate species contrasts starkly with adult and background color. This is counterintuitive - why make the most vulnerable members of a group conspicuous to threats? This project will investigate the form, and function of infant coloration in primates, giving insight into the role of infants in the social systems of primates - our direct evolutionary lineage. Many ideas for the function of infant conspicuousness have been proposed but not rigorously investigated. These include the color warning potentially infanticidal out-group males or predators that the infant will be defended by the group, confusing the paternity of infants to prevent infanticide, helping caregivers keep track of the infant, and facilitating the care of infants by mothers and non-mothers. This project will test these multiple hypotheses by objectively measuring the color of many individuals from many primate species throughout infancy, conducting comparative analyses of infant coloration across species, and behavioral experiments to find out how mothers, fathers and non-fathers respond to different colored infants. Color will be measured using calibrated and standardized digital photography at zoos, sanctuaries and research centers globally, with local researchers taking photos of infants throughout the period of development. These will then be processed using visual-system dependent methods to get a 'receiver-eye-view' of primate infant appearance. Comparative analyses across primate species will test the predictions made by each of the functional hypotheses about how infant color should relate to species' behavior, ecology and social system. For example, the paternity confusion hypothesis would predict that infants should be more conspicuous in species where paternity certainty is low. The experimental tests of function involve showing multiple species of captive primate images that have been manipulated to different infant and juvenile colors and measuring the interest of different receivers to different manipulations. The various hypotheses make unique predictions about who should be interested in what image properties, testing the function of primate infant conspicuousness with powerful experiments for the first time.