Huia cavitympanum lives in hillside primary forest. It has been recorded from 250 to 1,000 m elevations.
H. cavitympanum is easy to recognize: the eardrum is sunken in, the body coloration is contrasty, the legs are long. Males are approx. 50 mm, females 80 mm in snout-vent length.
Reproduction takes place in clear, rocky streams that are big enough to form torrential, foaming cascades. The spectacular tadpoles of this species live in very fast flowing waters. They cling to rock faces by their huge, strong abdominal sucker. The body shape is extremely streamlined. The tail is very strong. Tadpoles reach 70 mm in length.