The two species exhibited very similar behaviors, particularly concerning sexual dimorphism. In both T. cristatus and P. pygmaeus, the only one adult male present was less mobile and physically active than the rest of the group. Both primates spend a lot of the observed time grooming or resting and sleeping. These behaviors are typical for many primates, so the similarities are not surprising. T. cristatus was more active and were observed acquiring food and eating, while P. pygmaeus was not. This discrepancy could be explained by the different local observation times, which coincided with the feeding time in the Bronx Zoo (T. cristatus), but not in the San Diego Zoo (P. pygmaeus).
Another notable difference is in how the primates rested together. T. cristatus was often sitting on the same branch and in close physical contact with each other, except for some periods when the male primate rested alone. P. pygmaeus was observed resting next to each other, but they sat on different branches and did not engage in close physical contact. This difference could be attributed to the size difference of the primates – much larger P. pygmaeus could not comfortably fit everywhere. The more likely explanation is the temperature difference at the respective locations.
Colder weather in the Bronx Zoo might have prompted T. cristatus to seek close contacts to keep worm. To establish significant differences in T. cristatus and P. pygmaeus behaviors, more observations would be needed, conducted at the same time of day and in similar weather.