Albinism in a juvenile rhesus macaque Macaca mulatta (Zimmermann 1780) from the Brahmaputra Valley of Assam, India (Primates: Cercopithecidae)

Color aberrations are rare phenomena in wild mammals and are often associated with genetic disruptions affecting melanin production or deposition. The Rhesus Macaque Macaca mulatta, one of the most widespread primate species in India, has only rarely been reported to exhibit albinism or related pigmentary abnormalities in natural populations. Here, we document a case of albinism-like color aberration in a juvenile rhesus macaque observed in the Brahmaputra Valley of Assam, India. The individual, a juvenile male, displayed a uniformly light cream-colored coat and bluish eyes, rather than the complete depigmentation and red or pinkish eyes characteristic of true albinism. Based on phenotypic characteristics, the observed condition may be consistent with a form of oculocutaneous albinism potentially associated with mutations affecting melanin synthesis or transport, such as those involving the SLC45A2 gene; however, no genetic analyses were conducted, and this interpretation remains speculative. Behavioral observations indicated that the juvenile experienced significant social challenges within its troop, including aggression from adult males, possibly triggered by its atypical coloration. To our knowledge, while a previous case of albinism in a rhesus macaque has been reported from the Barak Valley of Assam, this represents the first documented record from the Brahmaputra Valley. This report highlights the need for further research into color aberrations in rhesus macaques and their potential implications for social interactions and survival in wild populations.