Coda vocalizations recorded in breeding areas are almost entirely produced by mature female sperm whales (Physeter macrocephalus)

Abstract

We investigated the use and function of coda communication by sperm whales (Physeter macrocephalus L., 1758 (=Physeter Catodon L., 1758)) Codas are stereotyped patterns of clicks often made by sperm whales in social contexts. We used the pulsed structure of coda clicks recorded from socializing female/immature groups to estimate the bodylength distribution of the animals producing the codas. Ninety-five percent of the 10653 codas that we measured were produced by whales measuring from 9 to 11 m. This size range corresponds to the length of mature females. We compared these data to a length distribution calculated from photographic measurements of individuals from the same groups encountered during the same studies. There were more whales shorter than 8.5 m (10.0%)and longer than 12.5 m (2.7%) in the photographic length distribution than in that of the coda producers (0.30% and 0.08% respectively). Since males leave their natal group when they are shorter than 9 m and return to breeding areas when they measure 13 m or more, our data shows that the codas were produced almost entirely by mature females. We suggest that coda communication serves several functions, including social bonding.