  Parallels of Zipf's law of brevity, the tendency of more frequent words to be
shorter, have been found in bottlenose dolphins and Formosan macaques. Although
these findings suggest that behavioral repertoires are shaped by a general
principle of compression, common marmosets and golden-backed uakaris do not
exhibit the law. However, we argue that the law may be impossible or difficult
to detect statistically in a given species if the repertoire is too small, a
problem that could be affecting golden backed uakaris, and show that the law is
present in a subset of the repertoire of common marmosets. We suggest that the
visibility of the law will depend on the subset of the repertoire under
consideration or the repertoire size.
