BEHAVIORAL RHYTHMS IN THE CAPTIVE COMMON MARMOSET (CALLITHRIX-JACCHUS) UNDER NATURAL ENVIRONMENTAL-CONDITIONS

Locomotor activity and autogrooming behaviors of three adult male capt ive common marmosets (Callithrix jacchus), kept under natural environm ental conditions and visually isolated from one another, were continuo usly observed for three nonconsecutive days from dawn to dusk, during at least 12 h. The subjects restricted their performance to the period between 05:00 h +/- 3 min and 16:45 h +/- 7 min. The small variabilit y observed in the plexograms suggests that the daily patterns are bimo dal for locomotor activity and unimodal for autogrooming. This may be characteristic of the species under the present experimental condition s. Spectral analysis revealed a significant (P < 0.05) 8-h rhythm peri od for locomotor activity, but the biological relevance of this could not be identified.