  Social relationships characterize the interactions that occur within social
species and may have an important impact on collective animal motion. Here, we
consider a variation of the standard Vicsek model for collective motion in
which interactions are mediated by an empirically motivated scale-free topology
that represents a heterogeneous pattern of social contacts. We observe that the
degree of order of the model is strongly affected by network heterogeneity:
more heterogeneous networks show a more resilient ordered state; while less
heterogeneity leads to a more fragile ordered state that can be destroyed by
sufficient external noise. Our results challenge the previously accepted
equivalence between the {\em static} Vicsek model and the equilibrium XY model
on the network of connections, and point towards a possible equivalence with
models exhibiting a different symmetry.
