Nuptial Pads

The swollen pink bumps on the inner sides of the thumbs are the nuptial pads used to grip onto females during coitus. In many species these nuptial pads are dark in color (black, gray, brown, etc) such as on Red Eyed Tree Frogs, Bull frogs, Pixie/Pacman frogs, and Dumpy/White's Tree Frog. The pads may also instead be very pale flesh colored (pink, peach, yellow, clear, white, etc), as in the Vietnamese Mossy Tree Frog specimen shown, depending on your species and color morph (for example an albino Pixie/Pacman frog may have pale colored nuptial pads even though dark pads are most common in the species). While this photo is taken from the underside of the feet, in some species (like Red Eyed Tree Frogs and Pixie/Pacman frogs) the pads may be easier to spot from the top of the feet, because in some species the pads aren't very swollen and are just rough, colored patches on the side to upper thumbs.