Prior to that, there was no isthmus of Panama, and South America was an island continent. As the Panamanian isthmus formed, many North American animals entered South America. Along with peccaries, lames and tapirs also migrated south. Today people think these animals are South American, yet all come from North American ancestors. The exchange was a two-way street however, and some of the ancient South American species, like the ground sloth, migrated north and are found at Hagerman.
Modern peccaries are social animals and often form herds.
Over 100 individuals have been recorded for a single herd of white-lipped peccary but smaller size groups are usually the case in the collared peccary and Chacoan peccary. Such social behavior seems to have been the situation in extinct peccaries as well. Pearce's Platygonus discovery at Hagerman included 3 individuals, an adult and two juveniles. The entire family group was preserved as one piece and is on display at the Smithsonian in front of the Hagerman mural. That Pearce's peccary must have been a common member of the Hagerman fauna 3.5 million years ago is also indicated by the numerous isolated bones and teeth that have been found throughout the Monument.