  Sterile neutrino dark matter, a popular alternative to the WIMP paradigm, has
generally been studied in non-supersymmetric setups. If the underlying theory
is supersymmetric, we find that several interesting and novel dark matter
features can arise. In particular, in scenarios of freeze-in production of
sterile neutrino dark matter, its superpartner, the sterile sneutrino, can play
a crucial role in early Universe cosmology as the dominant source of cold,
warm, or hot dark matter, or of a subdominant relativistic population of
sterile neutrinos that can contribute to the effective number of relativistic
degrees of freedom Neff during Big Bang nucleosynthesis.
