RESPONSES OF GIBBONS (HYLOBATES LAR) TO THEIR MIRROR IMAGES

Nine gibbons (Hylobates lar) and one gibbon-siamang crossbreed were ob served during exposure to their mirror images over two 30 min baseline condition periods (mirror off) and four 30 min treatment condition pe riods (mirror on). Greater frequencies and durations of gazing at the mirror and mirror-contingent behaviors were noted during reflective co nditions than for nonreflective conditions. Despite two subjects' appa rent use of the mirror to view body parts otherwise not visible to the m, no subjects passed a modified mark test. One subject exhibited limi ted aggressive displays toward the mirror, but no subjects exhibited a bnormal behaviors in the presence of the mirror. The results expand on and confirm similar findings by Lethmate and Ducker [Zeitschrift fur Tierpsychologie 33:248-269, 1973]. (C) 1998 Wiley-Liss, Inc.