  The Riviera model is a combinatorial model for a settlement along a
coastline, introduced recently by the authors. Of most interest are the
so-called jammed states, where no more houses can be built without violating
the condition that every house needs to have free space to at least one of its
sides. In this paper, we introduce new agents (predators and altruists) that
want to build houses once the settlement is already in the jammed state. Their
behavior is governed by a different set of rules, and this allows them to build
new houses even though the settlement is jammed. Our main focus is to detect
jammed configurations that are resistant to predators, to altruists, and to
both predators and altruists. We provide bivariate generating functions, and
complexity functions (configurational entropies) for such jammed
configurations. We also discuss this problem in the two-dimensional setting of
a combinatorial settlement planning model that was also recently introduced by
the authors, and of which the Riviera model is just a special case.
