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Chimpanzee Wears a Knotted Skin "Necklace"
W.C. McGrew and L.F. Marchant
Anthropology and Zoology,
Miami University
The tying of knots by animals is usually associated with construction of shelters (3), most notably nest-building by the Ploceinae
or weaver birds (2). Among primates, even in bed-making by Great Apes, we can find no previous record of knots; the closest is of
rehabilitated orangutans (Pongo pygmaeus) trying unsuccessfully to knot rope to secure a hammock (4). Here we report a knot tied
in a piece of skin of red colobus monkey (Procolobus badius tephrosceles) worn by a chimpanzee (Pan troglodytes schweinfurthii)
in the Mahale Mountains National Park, Tanzania.
On 7 November, 1996, chimpanzees of M group at Mahale killed and ate a red colobus monkey in the afternoon. When the
chimpanzees were found by observers again the next morning, several individuals were still carrying "left-overs". This is not
unusual, as skin is not eaten and youngsters, especially, may play with scraps of it. On the morning of 8 November we observed a
female juvenile, Ai, playing with, and grooming a strip of skin. She was pursued in play by a juvenile male, Primus, who "stole"
the skin. Some time later that same morning we observed Ako, a young adult female probably born in 1981, to be wearing what
appeared to be the skin draped around her neck. When she removed and abandoned it on the trail at 10:45 hr., we found it to be
tied in a single overhand knot. As can be seen from the figure, the knot creates a "necklace" of 68 cm circumference, with a "tail"
of 31 cm. length. We recovered the artifact, photographed it fresh, and then dried it in silica gel.
Draping is one of 21 modes of tool use described by Beck (1); it is not uncommon in both captive and wild apes (e.g. Beck's
book's cover photograph shows an orangutan with a cloth strip draped over the head). However, we know of no other non-human
case in which a draped adornment is made, that is, a necklace created by tying a knot. However, it should be made clear that we
did not see the knot tied. It may not have been done by Ako, and it may have occurred by accident, but the result was functional.
Like all anecdotes, it can only serve to alert us to a possibility; a single case is only an hypothesis, not a conclusion.
We are grateful to M. Bunengwa, M. Huffman, K. Kawanaka, M. Nakamura, H. Sasaki, and S. Uehara for assistance in the field,
and R. O'Malley for the drawings.
1. Beck, B.B., 1980. Animal Tool Behavior. Garland STPM Press, New York.
2. Crook, J.H., 1960. Nest form and construction in certain West African weaver birds. Ibis 102:1-25.
3. Hansell, M.H. 1984. Animal Architecture and Building Behavior. Longman, London.
4. Russon, A.E., and B.M.F. Galdikas, 1993. Imitation in free-ranging rehabilitant orangutans (Pongo pygmaeus) J. Comp.
Psychol. 107:147-161.
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... For instance it is clear that the faculty of self-awareness in a social animal would logically lead to strategies of consciously expressing individualism. Most such evidence is of a nature possessing very low taphonomic thresholds (Bednarik 1994b; but see McGrew and Marchant 1998;McGrew 2004 for apparent 'self-decoration' of a chimpanzee) [22,103,102], but beads and pendants are notable exceptions (Bednarik 1997(Bednarik , 2005(Bednarik , 2008a [27,30,31] providing glimpses of very early self-adornment. The several species indicating degrees of self-awareness (De Veer and Van Den Bos 1999; Gallup 1970Gallup , 1998Gallup et al. 2002;Heyes 1998; Keenan et al. 2003;Mitchell 1993Mitchell , 1997Mitchell , 2002 [62,[73][74][75]85,89,[105][106][107] are much the same as those shown to possess von Economo neurons (Seeley et al. 2006;Butti et al. 2009;Hakeem et al. 2009) [126,55,84]. ...
... For instance it is clear that the faculty of self-awareness in a social animal would logically lead to strategies of consciously expressing individualism. Most such evidence is of a nature possessing very low taphonomic thresholds (Bednarik 1994b; but see McGrew and Marchant 1998;McGrew 2004 for apparent 'self-decoration' of a chimpanzee) [22,103,102], but beads and pendants are notable exceptions (Bednarik 1997(Bednarik , 2005(Bednarik , 2008a [27,30,31] providing glimpses of very early self-adornment. The several species indicating degrees of self-awareness (De Veer and Van Den Bos 1999; Gallup 1970Gallup , 1998Gallup et al. 2002;Heyes 1998; Keenan et al. 2003;Mitchell 1993Mitchell , 1997Mitchell , 2002 [62,[73][74][75]85,89,[105][106][107] are much the same as those shown to possess von Economo neurons (Seeley et al. 2006;Butti et al. 2009;Hakeem et al. 2009) [126,55,84]. ...
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... This possibility was first hinted at by observations of a female orangutan at a zoo, who would decorate herself by gathering lettuce leaves from her cage to pile them onto her head while inspecting herself closely in the mirror [33] (Fig 4). Similarly, chimpanzees sometimes adorn themselves by walking around with the skin of monkey prey around their necks or develop a group-wide "fashion" to insert grass into their ears [34,35]. Only with a richer theory of the self and a larger test battery will we be able to determine all of the various levels of selfawareness, including where exactly fish fit in. ...
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We made an observational study of spontaneous imitation in orangutans (Pongo pygmaeus). Previous studies may have underestimated great apes' imitative capacities by studying subjects under inhibiting conditions. We used subjects living in enriched environments, namely, rehabilitation. We collected a sample of spontaneous imitations and analyzed the most complex incidents for the likelihood that true imitation, learning new actions by observing rather than by doing, was involved in their acquisition. From 395 hr of observation and other reports on 26 orangutans, we identified 354 incidents of imitation. Of these, 54 complex incidents were difficult to explain by forms of imitation based on associative processes grounded in experimental learning alone; they were, however, congruent with acquisition processes that include true imitation. These findings suggest that orangutans may be capable of true imitation and point to critical eliciting factors.
Ploceine nests are small globes with entrances at the side or below with or without some extension of the entrance in a spout or tube. An “initial ring” is first constructed and thereafter the male bird sits in this to carry out stitching and shaping. The form and dimensions of a nest are thus determined by the use of a fixed position and the distances to which the bird can reach up, out and around from it. The egg chamber develops first and the initial ring is thus the original entrance. Later construction involves the extension of the roof down over the front of the initial ring aperture to form porch, antechamber or funnel etc. (Construction in Amblyospiza albifront is aberrant.) Four types of nest are characterised: “globular”, “kidney-shaped”, “incomplete kidney-shaped” and “retort-shaped”. The latter may be subdivided into nests with a funnel entrance (Type A) and those with tubes (Type B). Nest construction is described in detail for Quelea quelea and compared with that of Ploceus {Sitagra) cucullatus and other species. The stages are classified and stitching and shaping movements described. The differences between stitching movements correlate with successive stages of construction and the differences are regarded as due to different orientations of the same basic movements to the developing nest. Proximate factors determining nest form are: the methods of attachment, the size of the bird, and the construction of much of the nest from a fixed position in the initial ring. Extension of the entrance is a function of the extent to which building continues after the completion of the egg chamber. It is thus in part an expression of the length of time spent building relative to the total duration of the breeding season. In considering the ultimate factors responsible for the evolution of nest forms a correlation is noted between long breeding seasons, predominantly insect diet, nest siting in trees and long tubular entrances. Likewise there is a rough correlation between short breeding seasons (and/or rapid breeding) and globular or kidney-shaped nests. A high speed of reproduction in a short breeding season seems correlated with a cessation of nest building at an earlier stage than where the breeding season is a long one. However, nests of a particular species often show characteristic features, which suggests that the nest of a species is the product of selection for its survival value in the habitat concerned. Nest form is thus considered not merely the expression of the speed of reproduction but in addition to be directly adapted to its site. The evidence for the four types of nest is discussed and the need for further study emphasised. Building behaviour is discussed. The production of a properly developed nest requires constant repetition of the building sequences, especially at the fixed building position, and also building activity sufficiently sustained to produce roof and walls and shaping sufficient to mould the form of the nest. Low motivation results in aberrant shapes through the use of irregular building positions and inadequate shaping.
  • B B Beck
Beck, B.B., 1980. Animal Tool Behavior. Garland STPM Press, New York.