Spot-Flanked Poison Dart Frog, Madidi National Park, BoliviaThis very small frog is called the spot-flanked poison dart frog. I came across him while hiking in Madidi National Park in the Bolivian Amazon. The blue vocal sac was pretty impressive, disappearing beneath the frog’s chin from time to time before bursting forth again. The rest of the coloration was also impressive. Without any flash, I used a very long shutter speed of four seconds to capture the frog when he was completely still.Nikon D300 with Nikkor 70-200mm lens (at 200mm with Canon 500D close up filter) ISO 200, f/16 at 4 seconds.