Kilometer-scale neutrino telescopes will detect muon and electron neutrinos from astrophysical sources at the TeV scale and above. Tau neutrinos are also expected from these sources due to neutrino oscillations over astrophysical baselines. Identification of tau neutrinos is expected to be possible above the PeV energy range through the "double bang" and "lollipop" signatures. We discuss another signature of tau in the PeV-EeV range, arising from the decay of tau leptons inside the detector to much brighter muons.