ESR 3:239-247 (2007)  -  DOI: https://doi.org/10.3354/esr00045

ABSTRACT: This study describes the activity pattern of the blue-eyed black lemur Eulemur macaco flavifrons for the first time and investigates the parameters, such as season or habitat, that may influence the distribution of activity over the 24 h cycle. Four groups of E. m. flavifrons in 2 forest fragments with different degrees of degradation were followed for 24 h mo^–1 over a 7 mo period between July 2004 and July 2005. Blue-eyed black lemurs exhibited a bimodal activity pattern which peaked during the morning and evening twilight. The groups consistently showed activity bouts both during the day and at night, a behaviour that corresponds to Tattersall’s (1987) definition of cathemerality. The proportion of illuminated lunar disc and the nocturnal illumination index were positively associated with the amount of nocturnal activity. Total activity, both diurnal and nocturnal, was significantly higher in the secondary than in the primary forest. In view of our results, the cathemeral behaviour of E. m. flavifrons may best be explained as flexible responses to a framework of varying environmental factors, each of which may enhance or inhibit activity within the lemurs’ range of adaptability. This temporal behavioural plasticity may be an adaptation to an erratic and severe climate with frequent droughts and cyclones and unpredictable resource availability.

KEY WORDS: Eulemur macaco flavifrons · Cathemerality · Activity pattern · Nocturnal illumation index · Primary forest · Secondary forest