  Within the standard propagation scenario, the flavor ratios of high-energy
cosmic neutrinos at neutrino telescopes are expected to be around the
democratic benchmark resulting from hadronic sources, $\left( 1 : 1 : 1
\right)_\oplus$. We show how the coupling of neutrinos to an ultralight dark
matter complex scalar field would induce an effective neutrino mass that could
lead to adiabatic neutrino propagation. This would result in the preservation
at the detector of the production flavor composition of neutrinos at sources.
This effect could lead to flavor ratios at detectors well outside the range
predicted by the standard scenario of averaged oscillations. We also present an
electroweak-invariant model that would lead to the required effective
interaction between neutrinos and dark matter.
