  Measurements of the loss rates for strontium n$^{3}$S$_{1}$ Rydberg atoms
excited in a dense BEC are presented for values of principal quantum number $n$
in the range $49\lesssim n \lesssim 150$ and local atom densities of $\sim1$ to
$3\times10^{14}$cm$^{-3}$. Two main processes contribute to loss, associative
ionization and state-changing. The relative importance of these two loss
channels is investigated and their $n$- and density-dependences are discussed
using a model in which Rydberg atom loss is presumed to involve a close
collision between the Rydberg core ion and ground-state atoms. The present
measurements are compared to earlier results obtained using rubidium Rydberg
atoms. For both species the observed loss rates are sizable,
$\sim10^{5}-10^{6}$s$^{-1}$, and limit the time scales over which measurements
involving Rydberg atoms immersed in quantum degenerate gases can be conducted.
