Masking of nocturnal activity by lunar eclipses in wild owl monkeys of the Argentinean Chaco.

<p>Activity patterns averaged across individuals for each of the three days when the total lunar eclipses occurred. Averages were calculated for the 2 h before the penumbra phase (left white bar with clock time for the onset of the 2-h window), for the 2-h after the end of the penumbra phase (right white bar with clock time for the offset of the 2-h window), as well as for the penumbra phase (light gray bars), the partial eclipse phase (dark gray bar) and the full eclipse (black bar). The averages represent the mean activity per 5-min interval for the specific phase, regardless of the phase duration. The date of each eclipse is indicated at the top of each graph and the number of recorded subjects is indicated between parentheses. The two hours prior to the eclipses from Nov 8, 2003 and Oct 27, 2004 occurred at times when brighter light intensity likely led to lower levels of activity.