Proceedings of the XVIII Congress of the International Primatological Society Adelaide,Australia, January 7–12, 2001

International Journal of Primatology -     

Stone Anvil Damage by Wild Bearded Capuchins (Sapajus libidinosus) during Pounding Tool Use: A Field Experiment

We recorded the damage that wild bearded capuchin monkeys (Sapajus libidinosus) caused to a sandstone anvil during pounding stone tool use, in an experimental setting. The anvil was undamaged when set up at the Fazenda Boa Vista (FBV) field laboratory in Piauí, Brazil, and subsequently the monkeys indirectly created a series of pits and destroyed the anvil surface by cracking palm nuts on it. We measured the size and rate of pit formation, and recorded when adult and immature monkeys removed loose material from the anvil surface. We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil. Whole nuts were preferentially placed within pits for cracking, and partially-broken nuts outside the established pits. Visible anvil damage was rapid, occurring within a day of the anvil''s introduction to the field laboratory. Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.     

String‐pulling behaviour in a Harris's Hawk Parabuteo unicinctus

Variations on the string‐pull experiment have been presented to a variety of avian species. Here, we present the results of a basic vertical string‐pull task with a Harris's Hawk Parabuteo unicinctus. A 2‐year‐old subject retrieved a shielded food reward within 8 min on each of eight trials and spontaneously used solving techniques similar to corvids and parrots. Our data contribute to the small body of literature on raptor cognition by showing that it may be within the realm of at least one bird of prey species to perform the string‐pull task similarly to avian species renowned for their high cognitive abilities.     

Understanding emotions in primates: in honor of Darwin's 200th birthday

In the bicentenary year of Darwin's birth, the American Society of Primatologists honored his memory by convening a symposium entitled "Understanding emotions in primates: In honor of Darwin's 200th birthday." The four articles in this special section, excepting this introduction, derive from that symposium. The section confirms that the topic of emotion is once again, as in Darwin's lifetime, the subject of wide-ranging, theoretically exciting research, and that studies with nonhuman primates are at the leading edge of a rapidly changing field.     

Distribution of potential suitable hammers and transport of hammer tools and nuts by wild capuchin monkeys

Selection and transport of objects to use as tools at a distant site are considered to reflect planning. Ancestral humans transported tools and tool-making materials as well as food items. Wild chimpanzees also transport selected hammer tools and nuts to anvil sites. To date, we had no other examples of selection and transport of stone tools among wild nonhuman primates. Wild bearded capuchins (Cebus libidinosus) in Boa Vista (Piauí, Brazil) routinely crack open palm nuts and other physically well-protected foods on level surfaces (anvils) using stones (hammers) as percussive tools. Here we present indirect evidence, obtained by a transect census, that stones suitable for use as hammers are rare (study 1) and behavioral evidence of hammer transport by twelve capuchins (study 2). To crack palm nuts, adults transported heavier and harder stones than to crack other less resistant food items. These findings show that wild capuchin monkeys selectively transport stones of appropriate size and hardness to use as hammers, thus exhibiting, like chimpanzees and humans, planning in tool-use activities.     

Variability and adaptability in the genus Cebus

Capuchins (Cebus) present an array of similarities to humans and apes in morphology, behavior and life history which raise a host of questions about the relations of these features to each other and about their evolutionary origins. As a genus and as individuals, capuchins possess marked adaptability and great variability in behavior. These two characteristics contribute directly to the biological success of capuchins. Variability and adaptability are also hallmarks of human behavior.     

Social Facilitation of Eating Familiar Food in Tufted Capuchins (<Emphasis Type="Italic">Cebus apella</Emphasis>): Does it Involve Behavioral Coordination?

Social facilitation of eating familiar foods might serve to synchronize eating activities within groups. We aimed to assess whether capuchins (Cebus apella) are prompted to eat when observing other conspecifics eating a familiar food. Subjects were 8 male captive-born tufted capuchins. One pair of capuchins acted as demonstrators for the other 6 observer subjects. In the Experimental condition, the demonstrator pair was given fresh chow in addition to having access to the leftover food and ate continuously. In the Control condition, the demonstrator pair had access to food leftover from the morning feed and ate very little. The initiation of feeding by the demonstrator pair prompted the initiation of feeding behavior in the observers, and the latter ate significantly more of their leftovers in the Experimental than in the Control condition. The tempo ofthe social facilitation of eating familiar foods in capuchins supportisomorphic coordination, a process that occurs when one individuals activity focuses the attention of another individual to the same activity, thereby increasing behavioral similarity in a group.