Circadian rhythms of drinking and body temperature of the owl monkey (Aotus trivirgatus)

Abstract The rhythms of drinking and body temperature of 4 male owl monkeys (Aotus trivirgatus) were examined under conditions of LD 12:12 ( L =100 lx, D =0.1 lx), DD (0.1 lx) and LL (100 lx). For all 4 monkeys, the circadian pattern expressed in LD 12:12 continued in DD, with a free-running period averaging 23.6 hr. In LL the circadian component of both rhythms decayed and, in one monkey, a low frequency pattern arose. In at least two aspects, masking and persistence, the owl monkey circadian timing system appears to be unlike that of its diurnal relative, the squirrel monkey. Circadian rhythms of owl monkeys also differ in some respects from those of other nocturnal mammals.