title: Proximate causes of the red face of the bald uakari monkey (Cacajao calvus).
abstract: In social species, such as primates, facial appearances transmit a variety of social signals. Although it is suggested that the intense red colour of the face of the bald uakari monkey might be an indicator of health, this hypothesis still has not been verified. This study describes the histological structure of the skin of the face in the bald uakari, compared with other non-red neotropical primates, to better understand the maintenance of its colour. The facial skin of the bald uakari monkey is characterized by a thinner epidermis, absence of melanin pigments and a high density of vascular capillaries that spread below the epidermis. These vascular capillaries are larger and more tortuous than in other neotropical primates. The skin of the face of the bald uakari monkey allows a direct external assessment of haematological status, suggesting that the colour of the face would be an honest indicator of health, but could also signal sexual or behavioural states.
authors.affiliation: Department de Sanitat i Anatomia Animals , Faculty of Veterinary, Universitat Autònoma de Barcelona , Bellaterra, Barcelona, Spain ; YAVACUS , Yavarí Conservación y Uso Sostenible , Iquitos, Perú
authors.forename: P
authors.initials: P
authors.lastname: Mayor
authors.affiliation: Laboratory of Pathology, Faculty of Veterinary , Universidad Peruana Cayetano Heredia , Lima, Perú
authors.forename: J
authors.initials: J
authors.lastname: Mamani
authors.affiliation: YAVACUS , Yavarí Conservación y Uso Sostenible , Iquitos, Perú
authors.forename: D
authors.initials: D
authors.lastname: Montes
authors.affiliation: Departament de Medicina i Cirurgia Animals , Servei d' Ecopatologia de Fauna Salvatge (SEFaS), Faculty of Veterinary, Universitat Autònoma de Barcelona, Bellaterra , Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: González-Crespo
authors.affiliation: SAMAI , Iquitos, Perú
authors.forename: M A
authors.initials: MA
authors.lastname: Sebastián
authors.affiliation: San Diego Zoo Global , Institute for Conservation Research , Escondido, CA, USA ; School of Psychology and Neuroscience , University of St Andrews , St Andrews, UK.
authors.forename: M
authors.initials: M
authors.lastname: Bowler
keywords: Cacajao calvus; coloration; face; health indicator; uakari