  Suppose each vertex of a graph is originally occupied by contamination,
except for those vertices occupied by lions. As the lions wander on the graph,
they clear the contamination from each vertex they visit. However, the
contamination simultaneously spreads to any adjacent vertex not occupied by a
lion. How many lions are required in order to clear the graph of contamination?
We give a lower bound on the number of lions needed in terms of the Cheeger
constant of the graph. Furthermore, the lion and contamination problem has been
studied in detail on square grid graphs by Brass et al. and Berger et al., and
we extend this analysis to the setting of triangular grid graphs.
