Another shot from my recent nighttime photowalk at the Denver Zoo:
Unlike some of the other zoo residents, this little critter (a Mossy Frog) was more than happy to sit still for me while I tried a few different flash settings on him. From the placard:
This frog from Vietnam has evolved skin warts, protrusions, and colors that closely mimic mosses and lichens on trees. They are extremely difficult to see when settled into grooves in tree bark, where they sleep during the day.