Despite the vast research into rhesus macaque (Macaca mulatta) social behavior, little is known about how they adapt to novel environments, particularly in cases where they experience little or no between-group competition and are not provisioned. A rhesus macaque population was introduced into Silver Springs State Park (SSSP) in central Florida in the mid-1930s and has spread into the Ocala National Forest. The study group, 14km northeast of the original population in SSSP, along the Dead River experiences no observed intergroup competition, is not provisioned, and has access to abundant and distributed food throughout the riverine floodplain. Rhesus macaques are considered the archetypal species for phylogenetic inertia, an evolutionary adaptation to past ecological conditions, which then produced a static behavioral pattern. Over 231.5 hours of observation during June and July of 2016, the Dead River macaque group was observed to break from the species-typical pattern of high levels of agonism and a steep, stable hierarchy, and instead demonstrated a shallow hierarchy with infrequent agonism in a feeding context. This indicates that rhesus macaques are capable of significantly changing behavior when living under novel ecological conditions. A deeper understanding of the relationship between primate species and their environment is essential to addressing the anthropogenic pressure placed on other species that experience phylogenetic inertia but are also at risk from human encroachment and anthropogenic climate change.