Monkeys with disabilities: prevalence and severity of congenital limb malformations in Macaca fuscata on Awaji Island

The Awajishima Monkey Center (AMC) free-ranging, provisioned population of Japanese macaques has included individuals with congenital limb malformations (CLMs) for at least 40 years. Including new data from this study, 16.1% of AMC infants from 1969 to 2007 (185 of 1,150) were born with CLMs. However, relatively little is known about the demographics of CLMs in the population, particularly the relationships among occurrence and severity of CLMs and age-sex demographics after infancy. In 2004, we conducted a census at AMC. Of the 199 monkeys censused, 34 individuals (17.1%) had CLMs. To estimate the severity of CLMs, we created an index that ranks individuals on a scale of 0 to 1 based on affected and absent limbs and digits. The severity of CLMs varied greatly (index range = 0.01-0.79, mean = 0.29), with similar variation in severity in each age-sex class (Student t-test, P > 0.05).