  We investigate the hot carrier dynamics of ZrTe$_5$ by ultrafast
time-resolved optical reflectivity. Our results reveal a phonon-mediated
across-gap recombination, consistent with its temperature-dependent gap nature
as observed previously by photoemission. In addition, two distinct relaxations
with a kink feature right after initial photoexcitation are well resolved,
suggesting the complexity of electron thermalization process. Our findings
indicate that correlated many-body effects play important role for the
transient dynamics of ZrTe$_5$.
