  CAIRNS (Cluster And Infall Region Nearby Survey) is a spectroscopic survey of
the infall regions surrounding nine nearby rich clusters of galaxies. In Paper
I, we used redshifts within $\sim 10\Mpc$ of the centers of the clusters to
determine the mass profiles of the clusters based on the phase space
distribution of the galaxies. Here, we use 2MASS photometry and an additional
\ncziinew redshifts to investigate the environmental dependence of
near-infrared mass-to-light ratios. In the virial regions, the halo occupation
function is non-linear; the number of bright galaxies per halo increases more
slowly than the mass of the halo. On larger scales, the light contained in
galaxies is less clustered than the mass in rich clusters. Specifically, the
mass-to-light ratio inside the virial radius is a factor of $1.8\pm0.3$ larger
than that outside the virial radius. This difference could result from changing
fractions of baryonic to total matter or from variations in the efficiency of
galaxy formation or disruption with environment. The average mass-to-light
ratio $M/L_K = 53\pm 5 h$ implies $\Omega_m = 0.18\pm 0.03$ (statistical) using
the luminosity density based on 2dFGRS data. These results are difficult to
reconcile with independent methods which suggest higher $\Omega_m$. Reconciling
these values by invoking bias requires that the typical value of $M/L_K$
changes significantly at densities of $\lesssim3\rho_c$.
