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Circadian activity rhythms in squirrel monkeys: entrainment by temperature cycles
1Max-Planck-Institut für Verhaltensphysiologie, Andechs, Federal Republic of Germany.
Journal of Biological Rhythms
|January 1, 1986
Summary
Squirrel monkeys exhibit free-running activity rhythms longer than 24 hours under constant conditions. Ambient temperature cycles can entrain activity, but light-dark cycles are more effective, with masking effects also observed.
Area of Science:
- Primates
- Animal Behavior
- Chronobiology
Background:
- Squirrel monkeys' activity patterns are crucial for understanding primate circadian rhythms.
- Previous research has explored light-dark cycle entrainment, but the role of temperature cycles is less understood.
Purpose of the Study:
- To investigate the entrainment of squirrel monkey locomotor activity by light-dark cycles and ambient temperature cycles.
- To determine the effects of constant conditions and varying light intensity on free-running rhythms.
Main Methods:
- Locomotor activity of eight squirrel monkeys was recorded in a climatic chamber under three conditions: constant, light-dark cycles, and temperature cycles.
- Animals were exposed to varying light intensities and ambient temperatures.
Main Results:
- Under constant conditions, activity rhythms had periods longer than 24 hours, influenced by light intensity.
- Light-dark cycles effectively entrained activity, while temperature cycles entrained activity in approximately 45% of tests.
- Temperature changes caused masking effects, increasing activity during warmer periods.
Conclusions:
- Squirrel monkey activity rhythms are primarily entrained by light-dark cycles.
- Ambient temperature cycles can influence activity patterns, but with masking effects.
- Light intensity plays a role in modulating free-running rhythm periods.