Abstract # 3136 Event # 31:

Scheduled for Saturday, September 17, 2011 02:00 PM-02:15 PM: Session 8 (Meeting Room 408) Oral Presentation


EFFECTS OF NOCTURNAL LIGHT INTENSITY ON CALLING FREQUENCY IN DRY FOREST PHANER AND LEPILEMURS

C. C. Veilleux
University of Texas at Austin, Department of Anthropology, 1 University Station C3200, Austin, TX 78712, USA
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In contrast to other nocturnal mammals, nocturnal primates often increase activity in brighter moonlight (“lunar philia”). While researchers suggest this difference may relate to primates’ increased visual emphasis, lunar behavior is documented in only a limited number of species. In this study, I measured nocturnal light intensity and lemur calling frequency over 25 nights (Aug-Sep 2009) at Kirindy Mitea National Park, a dry forest in Madagascar. For each night, light intensity (w/cm2) was sampled at 18 locations using a research radiometer. During each measurement period (approximately 3-5 minutes), I recorded vocalization presence/absence for two species, the fork-marked lemur (Phaner pallescens) and the sportive lemur (Lepilemur ruficaudatus), resulting in 404 observations. The data reveal that periods when Phaner vocalized had significantly higher light intensities than quiet periods (Wilcoxon rank sum test: W=15438.5, p=0.005). For Lepilemur, light intensity did not significantly vary between calling and quiet periods (W=13314.5, p=0.141). I also ran generalized linear mixed models to control for sampling autocorrelation. The results of these models mirror the raw analyses: light intensity had a significant effect on calling in Phaner (p=0.0038) but not Lepilemur (p=0.457). Together, these analyses reveal interspecific behavioral variation in response to nocturnal light intensity at Kirindy Mitea. While Phaner appears lunar philic, Lepilemur is lunar neutral. I propose that this difference stems from a greater emphasis on vision in Phaner foraging behavior.