Oophaga pumilio are slender frogs with bilateral symmetry. They are small frogs measuring 17 to 24 mm in length at adulthood. They feature four, un-webbed digits on each hand and foot, and the body is overall quite compact. These frogs have fairly large, dark eyes set on the sides of the head. The skin of a poison dart frog is very moist which gives them a somewhat glossy appearance in bright light. This species is sexually monomorphic.
They are typically bright red with blue legs although they vary greatly in coloration, and are known as being one of the most polymorphic, aposematic species. However, populations of O. pumilio tend to be the same color. Though typically strawberry red, the dorsal coloration can vary in color from red to blue, yellow, white, green, black or orange. The dorsal surface may also feature dark spots or mottling. Legs are typically darker and have some degree of blackish mottling. Their aposematic coloration has convergently evolved between some separate populations.
Tadpoles are dark brown above with lighter brown undersides and dark spots scattered throughout. They have small, ventral, oral discs with large, serrated beaks. They can reach 16 mm in length.
Range length: 17 to 24 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; poisonous
Sexual Dimorphism: sexes alike