Over a 7-month period, stick tools constructed by chimpanzees were collected and measured at the Ngotto Forest site in Central African Republic. The chimpanzees were found to use tools to dip for ants and to probe for honey. The basic descriptions of these tools and the contexts in which they were found are presented. The lengths of two of the tool types were compared with the use of a t-test for independent groups. It was found that the lengths of the tools differed significantly depending upon their function. The location and habitat type of each tool site were plotted on a map. The tool types were distributed throughout the southern part of the study area, and with one exception all tool sites were found in the same type of habitat. Two tool sites with two other types of tools (honey hammer/club and ant club) were found. The tool types at Ngotto are compared with those found at other chimpanzee field sites, and the implications for diversity in chimpanzee material culture are discussed.

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This study examined the use of sensory modalities relative to a partner's behavior in gesture sequences during captive chimpanzee play at the Chimpanzee and Human Communication Institute. We hypothesized that chimpanzees would use visual gestures toward attentive recipients and auditory/tactile gestures toward inattentive recipients. We also hypothesized that gesture sequences would be more prevalent toward unresponsive rather than responsive recipients. The chimpanzees used significantly more auditory/tactile rather than visual gestures first in sequences with both attentive and inattentive recipients. They rarely used visual gestures toward inattentive recipients. Auditory/tactile gestures were effective with and used with both attentive and inattentive recipients. Recipients responded significantly more to single gestures than to first gestures in sequences. Sequences often indicated that recipients did not respond to initial gestures, whereas effective single gestures made more gestures unnecessary. The chimpanzees thus gestured appropriately relative to a recipient's behavior and modified their interactions according to contextual social cues.

Signing between chimpanzees was systematically sampled. Four of the five chimpanzees in this group had had 4–7 years of complete immersion in American Sign Language (ASL) when they were being home reared (Gardner & Gardner 1971:125–127). It was found that the chimpanzees signed to each other, integrating their signing interaction into their nonverbal communication. Eighty-eight per cent of all signs reported fell into the social categories of reassurance, social interaction, and play.