  Two of the most fundamental properties of the dark matter particle, the mass
and the lifetime, are only weakly constrained by the astronomical and
cosmological evidence of dark matter. We derive in this paper lower limits on
the lifetime of dark matter particles with masses in the range 10 TeV-10^15 TeV
from the non-observation of ultrahigh energy neutrinos in the AMANDA, IceCube,
Auger and ANITA experiments. For dark matter particles which produce neutrinos
in a two body or a three body decay, we find that the dark matter lifetime must
be longer than O(10^26-10^28) s for masses between 10 TeV and the Grand
Unification scale. Finally, we also calculate, for concrete particle physics
scenarios, the limits on the strength of the interactions that induce the dark
matter decay.
