Primate tool use is of great interest to many fields of science, but has only been documented in a limited number of species. Here, we present the first documentation of tool use in crested
capuchin monkeys (Sapajus robustus) in a captive population of 7 individuals at the Santa Ana
Zoo in California. In just over 54 hours of observation and without any prior training, the
monkeys performed eleven distinct types of tool use, including digging, dipping, hammering,
probing, raking, sponging, striking, sweeping, throwing, waving, and wedging. Furthermore, we
observed tool modification and consecutive tool use as well as opportunities for social learning
including tolerated scrounging and direct observation of tool use. Our results support the
opportunity hypothesis over the necessity hypothesis in explaining the presence of animal tool
use. While there is currently no evidence that wild crested capuchins also use tools, these
findings suggest they might. This study highlights the need for further research on this
understudied, endangered species. Supplementary material includes the SAZ enrichment list, a
schematic of their enclosure, and 26 videos showing each kind of tool use.