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

Abstract

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 10 653 codas that we measured were produced by whales measuring from 9 to 11 m. This size range corresponds to the lengths 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 show that the codas were produced almost entirely by mature females. We suggest that coda communication serves several functions, including social bonding.Résumé : Nous avons étudié l'utilisation et les fonctions de la communication par « codas » du cachalot (Physeter macrocephalus L., 1758 (= Physeter catodon L., 1758)). Les codas sont formées d'une série de cliquetis qui possèdent un pattern stéréotypé. Nous avons suivi des groupes sociaux de femelles et de jeunes et enregistré leurs codas afin d'estimer la distribution des tailles des cachalots qui les produisent à partir de la structure pulsée des cliquetis. Quatre-vingt-quinze pour cent des 10 653 codas analysées ont été produites par des cachalots mesurant de 9 à 11 m. Ces longueurs correspondent à la taille des femelles matures. Nous avons comparé ces résultats avec la distribution des longueurs calculée à partir de photos prises lors des mêmes études. Il y avait plus de cachalots mesurant moins de 8,5 m (10,0 %) et plus de 12,5 m (2,7 %) dans les estimations faites à partir de photos que dans celles réalisées à partir des codas (0,30 % et 0,08 %, respectivement). Les codas semblent émises presque exclusivement par les femelles matures puisque les mâles quittent les groupes de femelles et de jeunes lorsqu'ils mesurent moins de 9 m et y reviennent lorsqu'ils mesurent plus de 13 m. Nous pensons que la communication par codas sert entre autres au renforcement des liens sociaux.

Off-axis effects on the multi-pulse structure of sperm whale coda clicks

“…The finding here of off-axis effects clearly indicates otherwise and partially explains the considerable number of coda clicks discarded in previous IPI analyses of coda clicks ͑Rendell and Whitehead, 2004;Marcoux et al, 2006͒. Moreover, the results presented here should encourage researchers to record sperm whale codas on-axis, most likely from behind the whale, and exclude from IPI analysis coda clicks recorded off-axis with poor pulse structure.…”

“…Although the waveforms of usual clicks have been examined from different recording aspects ͑Zimmer et al., 2005a;Madsen et al, 2002͒, it is unknown whether the pulse structure of coda clicks also demonstrates off-axis effects indicative of sound energy leakage at the frontal sac. Most codas are recorded from an unknown recording aspect or from behind the vocalizing whale ͑see Marcoux et al, 2006͒, prohibiting the observation of off-axis effects. To address this research gap, we inspected and compared the waveforms of coda clicks recorded on different hydrophones in a passive dynamic acoustic array.…”

Spatial and seasonal patterns in acoustic detections of sperm whales Physeter macrocephalus along the continental slope in the western North Atlantic Ocean

“…Slow clicks are produced only by mature males (Weilgart & Whitehead 1988), while codas are most frequently recorded among female groups (Whitehead & Weilgart 1991, Marcoux et al 2006, and coda types can provide information on social organization, such as to which acoustic clan the individuals belong (Rendell & Whitehead 2003. Here, we did not analyze the recordings for slow clicks and codas, because these click types were difficult to visually distinguish in the LTSAs, due to their energy content at lower frequencies which coincided with higher levels of ambient noise, and to the lower source levels of coda clicks (Madsen et al 2002a).…”

The Evolution of Individual and Cultural Variation in Social Learning

“…In other cases sex-specific social 10 organisation restricts social learning to one sex. For example, male humpback whales are quasi-11 solitary and so fail to learn female-specific vocalisations that delineate the social groups in which 12 females live [87]. More interesting are cases in which both sexes of a species have opportunities to 13 learn a trait that is non-sex-specific.…”