Due to a lack of data body size and weight measurements of Azara's night monkey have been estimated from a small number of wild samples. The average head and body length of the female is 341 mm (13.4 in) while the male is 346 mm (13.6 in).[citation needed] The average weight is 1,254 g (2.765 lb) for male A. a. azarae, 1,246 g (2.747 lb) for female A. a. azarae, 1,180 g (2.60 lb) for male A. a. boliviensis, and 1,230 g (2.71 lb) for female A. a. boliviensis.[3] Its gestation period is about 133 days. The lifespan for Azara's night monkey is unknown, but the captive life span for members of the genus Aotus is believed to be 20 years.[3]