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Preliminary study on the effects of photo traps used to monitor Mediterranean monk seals Monachus monachus

I evaluate the possible deterrent effect of visual-flash photo traps used to monitor Mediterranean monk seals Monachus monachus in their caves. Two systems of photo trapping were deployed in a cave, one using a flashing visible light and the other using an infrared light source. These systems were used alternately, each for an average duration of 1 wk at a time. A total of 453 digital photographs were taken by the photo traps throughout the experiment, which was conducted from July 2007 to February 2008. Based on an analysis of these photographs, 4 individuals of different age classes were identified. The individuals monitored never displayed an escape response following the flash; although some briefly responded to the flash, they quickly resumed their resting behaviour. Analysis of 47 haul-out events indicated that the average haul-out time of seals repeatedly exposed to a visible flash is longer than that of seals exposed to infrared flash. Although the small sample size limits conclusions, the striking difference found between haul-out times may be a sign of a negative effect which influences resting time of individuals.