Male specimens have an obvious depression on the head behind the large mandibles.

Male mandibles are large and curved with an obvious mid dorsal horizontal tooth [2] Geodorcus alsobius has a very restricted range.

Adult specimens of the Moehau stag beetle are found under wet rotten logs and rocks at altitudes between 760m and 840m.

[3] Priorities for conservation of this species involves surveying Mt Moehau to obtain information on the distribution and population size.

[5] In 2012, the threat status of this species was upgraded from range restricted to nationally endangered.