As a Grand Duke of Lithuania, Daumantas is mentioned in chronicles only once, and in absence of any other evidence, he is presumed to be a short ruled Grand Duke. Maybe, he is identical to Daumantas of Pskov, – there is a lot of uncertainty who inherited the title of Grand Duke after Traidenis' death in 1281 or 1282.
Ruthenian chronicles tell that in March 1285, when Daumantas attacked the Oleshnya volost' of Tver principality, i.e. the domain of Tver's bishop, Daumantas' army was defeated by united forces of Tver, Moscow, Novgorod, Torzhok, etc., and he was taken into captivity (however, majority of historians believe he died that year).
Daumantas was succeeded by Grand Duke Butegeidis. Relationships between Daumantas and Butegeidis or between Daumantas and Traidenis are unknown.