White-Fronted Brown Lemur, Nosy Mangabe, Madagascar These lemurs exhibit behavior that has one of the great names in nature — cathemerality. It means they have no regular pattern of sleep, or daily activity. They are randomly active during every 24 hour cycle. I only saw a few white-fronted brown lemurs in my trip to Madagascar back in 2007, all on the island of Nosy Mangabe. Nikon D200 with Nikkor 600mm manual focus lens, ISO 400, f/5.6 at 1/200th of a second.