Pack members shape the acoustic structure of a wolf chorus

Wolf packs perform group vocalizations called chorus howls. These acoustic signals have a complex structure and could be involved in functions such as strengthening of social bonds, territory advertisement, or spacing between packs. We analyzed video recordings of 46 chorus howls emitted by 10 packs of wolves held in captivity, in order to investigate whether sex, age, social status, pack, or individual influence the way wolves participate in a chorus. We found that, during a chorus, wolves vocalized 63% of the time, with the howl being the most common vocalization (36% of the chorus duration), followed by woa (13.5%), other vocalizations (11.8%), and bark (1.7%). The main factor affecting the vocal behavior of wolves was age, since young wolves vocalized less and uttered shorter acoustic signals than adults. The discriminant analysis carried out with the wolves of Cañada Real pack assigned 89.3% of the cases to the correct individual, which is much better than the assignment expected by chance, suggesting that individuals could have a unique vocal usage during a chorus howl, mainly due to the use of howls and woa-woa howls. Based on our results, we propose that in the context of a chorus the woa-woa howl is important, although further research is needed to address this issue properly.