Complex leaf‐gathering skills of mountain gorillas (Gorilla g. beringei): Variability and standardization

Abstract

The skills that mountain gorillas use to deal with the stings, tiny hooks, and spines protecting common plant leaves in their diet were examined for variation within and between animals. Many elements of uni-and bimanual performance were identified, often involving delicate precision and coordination, and varying idiosyncratically, each individual having a different set of preferred elements. Many of these elements are functionally equivalent, and all but one weaned animals showed full processing capability; the history of the one exception suggests that early experience with the task may be important. Gorillas' idiosyncrasy in manual skill elements is entirely consistent with trial-and-error learning a t this level. By contrast, each individual uses very few techniques (structured sequences of elements) for most processing, and these techniques are the same across the population. Where animals deviate from this generalization, they largely employ the simpler technique normally used for undefended leaves. Lateralization increases from start to finish, consistent with a logical structure in which each stage has a laterality bias and each stage is sequentially dependent on the last. Variations from their commonest techniques occur in all animals (on average, about nine variant techniques were recorded from each animal). The repertoire of techniques increases significantly with age, whereas the repertoire of elements does not. This points to an initial reliance on a single logical structuring that is well established by weaning (about 3.5 years), with subsequent development of the ability to vary the technique used so as to take advantage of variations in the environment. Standardization of logical organization, despite variability between different animals in individual elements and behavioral laterality, suggests that the logical ordering of elements and the interrelationships of processing stages is copied by program-level imitation.0 1993 Wiley-Liss, Inc.

Escolha de alvos coespecíficos na observação do uso de ferramentas por macacos-prego (Cebus libidinosus) selvagens

“…Nos últimos anos foram desenvolvidos muitos estudos sobre o uso de ferramentas para a quebra de cocos com macacos-prego em situação de semiliberdade com provisionamento (Ottoni & Mannu, 2001;Resende e Ottoni, 2002;Falótico, 2006;Silva & Ottoni, 2005 as mãos e a boca parece ser uma estratégia de forrageamento importante, comparável ao processamento de frutos de Neesia por orangotangos (van Schaik, 1996) ou de folhas com pelos urticantes, por gorilas (Byrne & Byrne, 1993). Seria interessante verificar se outros grupos de macacos-prego vivendo em ambiente semelhante, que ocorram os frutos descritos …”

Representing space and objects in monkeys and apes

“…In a more naturalistic setting, Byrne and Byrne (1993;see also Byrne, 1994) investigated both the actions used and the sequences of manipulation in the food processing of mountain gorillas. These authors observed that different plants required different manipulations depending on their natural defenses (e.g., thorns or spines).…”

“…For instance, when eating nettles that are covered with spines, gorillas use both hands, each one performing different actions. Byrne and Byrne (1993) indicated that there was a hierarchical organization in the execution of these manipulations, leading these researchers to postulate that gorillas represented the different steps in the manipulation sequence and executed them as plans. One piece of information that is missing from this naturalistic study is the ontogeny of these manipulations, which could help us understand how the subroutines are established and integrated.…”

“…Future developmental studies should focus on the relation between early manipulative skills and the ability to solve the types of problems designed by Visalberghi and colleagues in a variety of primates. Baboons and gorillas are obvious candidates for these kinds of studies due to their highly complex manipulative propensities (Byrne & Byrne, 1993;Westergaard, 1992).…”

Episodic-like memory in a gorilla: A review and new findings

“…Investigations have been directed at concept formation (Vonk, 2002(Vonk, , 2003Vonk & MacDonald, 2002), food processing (Byrne & Byrne, 1993;Pika & Tomasello, 2001), learning (Fischer, 1962;Fischer & Kitchener, 1965;Patterson & Tzeng, 1979;Rumbaugh & Steinmetz, 1971;Yerkes, 1927), linguistic skills (Patterson, 1978), mirror self-recognition (InoueNakamura, 1997; Ledbetter & Basen, 1982;Shillito, Gallup, & Beck, 1999;Suarez & Gallup, 1981;Swartz & Evans, 1994), problem-solving (Robbins, Compton, & Howard, 1978), social cognition (e.g., Maestripieri, Ross, & Megna, 2002;Mitchell, 1991;Stoinski, Wrate, Ure, & Whiten, 2001), and tool use (Fontaine, Moisson, & Wickings, 1995;Nakamichi, 1999). Our focus will be only on issues of memory, especially those relevant to the understanding of episodic memory and mental time travel.…”