  In this paper we investigate environment driven gas depletion in satellite
galaxies, taking full advantage of the atomic hydrogen (HI) spectral stacking
technique to quantify the gas content for the entire gas-poor to -rich regime.
We do so using a multi-wavelength sample of 10,600 satellite galaxies, selected
according to stellar mass (log M$_{\star}$/M$_{\odot}$ $\geq$ 9) and redshift
(0.02 $\leq$ z $\leq$ 0.05) from the Sloan Digital Sky Survey, with HI data
from the Arecibo Legacy Fast ALFA (ALFALFA) survey. Using key HI-to-stellar
mass scaling relations, we present evidence that the gas content of satellite
galaxies is, to a significant extent, dependent on the environment in which a
galaxy resides. For the first time, we demonstrate that systematic
environmental suppression of gas content at both fixed stellar mass and fixed
specific star formation rate (sSFR) in satellite galaxies begins in halo masses
typical of the group regime (log M$_{h}$/M$_{\odot}$ < 13.5), well before
galaxies reach the cluster environment. We also show that environment driven
gas depletion is more closely associated to halo mass than local density. Our
results are then compared with state-of-the-art semi-analytic models and
hydrodynamical simulations and discussed within this framework, showing that
more work is needed if models are to reproduce the observations. We conclude
that the observed decrease of gas content in the group and cluster environments
cannot be reproduced by starvation of the gas supply alone and invoke fast
acting processes such as ram-pressure stripping of cold gas to explain this.
