the foundation for observation studies of otters was conducted by scientists k. r. l. hall and george b. schaller in 1964. the scientists spent six days observing the californian otters in point lobos state park, california. over the course of their time, they observed 30 separate instances of tool use behaviors, most of which involved otters using rocks to crack mussels. since then, californian sea otters have been studied extensively for their tool use behavior, garnering more attention to the subject, and serving as a model for what kinds of tool use behaviors the sea otter species is capable of performing.