Lunar periodic modulation of the circadian activity rhythm in a wild North Colombian night monkey (Aotus griseimembra)

ABSTRACT

South American night monkeys (genus Aotus) are the only nocturnal simian primates. Early activity recordings in North Colombian A. griseimembra monkeys kept under semi-natural conditions and extensive chronobiological studies carried out in laboratory settings revealed a strictly nocturnal behavior and strong activity enhancing (disinhibiting) effects of moonlight or corresponding luminosities during the dark time. To check whether the results from captive individuals correspond to the behavior of wild monkeys, we carried out long-term activity recordings of a wild female A. griseimembra in a tropical rainforest near San Juan de Carare, Northern Colombia. Our data from about 150 days of continuous activity records with an “Actiwatch Mini” (CamNtech, UK) accelerometer-data logger device, confirmed: (1) strictly nocturnal behavior, (2) a pronounced bimodal activity pattern with prominent peaks during dusk and dawn, and (3) a lunar periodic modulation (masking) of the night monkey’s circadian activity rhythm due to distinct activity inhibiting effects of the absence of moonlight throughout the night. The results from this wild-living tropical night monkey are consistent with those from captive conspecifics studied decades earlier.

KEYWORDS:

• Actimeter
• circadian activity rhythm
• light masking
• lunar cycle effects
• owl monkey

Acknowledgements

We are very grateful to the Lalinde and De Greiff families, who have allowed us to conduct research on primates and other mammals at their Hacienda San Juan de Carare, and have been committed to the conservation of wetlands and forest remnants since 2007. We thank Eduardo Fernández-Duque for valuable advice, Manuela de Meo, Silvia Rondón, and Arnulfo Montoya for key assistance during the placement of the actimetry collar, and Jorge Martinez Contreras, from the Universidad Externado de Colombia, for helpful assistance on programming the actimeters and reading data from them. Also, many thanks to Leonardo Nuñez for technical support, to Raul Cardoso for figure design, and to José Carlos Sánchez Ferrer, from the Faculty of Science, UNAM, for carrying out the Cosinor analyses. Last but not least, we are very grateful for financial support given to the research project the Primate Action Fund, the Mohamed Bin Zahed Species Conservation Fund, and the Consejo Nacional de Ciencia y Tecnología CONACYT of Mexico (JMD project 0220300).

Declaration of Interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was supported by the Consejo Nacional de Ciencia y Tecnología [0220300]; The Mohamed Bin Zahed Species Conservation Found; Margo Marsh - Primate Action Fund.