  Dark matter can decay via gravity portals and contribute a minor decay (MD)
width. This paper proposes that nonminimal coupling between the Higgs field and
gravity can lead to additional gravity-Higgs portals for gravitational dark
matter to decay and contribute additional decay (AD) width. For scalar dark
matter candidates with a mass less than 5 TeV, the decay branching ratios are
almost independent of whether dark matter decay through gravity portals or
gravity-Higgs portals; therefore, it is almost impossible to distinguish
gravity portals from gravity-Higgs portals by observing decay products. For
fermionic singlet dark matter candidates, their MD products are diverse, while
their AD products are monotonous, only neutrinos and Higgs bosons. As for both
dark matter candidates, gravity-Higgs portals prefer to dominate the decay at
around several hundred GeV. Besides, for both TeV dark matter candidates, there
is still a vast parameter space alive.
