Sperm whale (Physeter macrocephalus) codas and creaks in the Northern Gulf of Mexico: Classification, comparison, and co-occurrence.

摘要

The present study set out to classify sperm whale codas recorded by bottom-moored hydrophones in the Northern Gulf of Mexico (NGoM) during July and August of 2001 using protocols similar to those followed in other studies. After classification, comparisons were made between the repertoire identified herein and those identified in other studies, both in the NGoM and in other parts of the world.;This study identified 5,035 codas representing 34 distinct coda types. The similarity in coda patterns between this study and another from the same location, combined with historical sightings and a lack of temporal variability in coda production identified in other studies, supports the theory that a resident population of sperm whales (Physeter macrocephalus) might inhabit the NGoM. Coda types were more similar between the present study and the Apple (2002) analysis also conducted in the same region, than between the present study and those conducted in other areas of the world. Time-of-day and location analyses were also performed on the identified codas. The similarities and differences in coda production also lend support to the premise that the coda repertoire used by sperm whales seems to vary geographically, but remains relatively stable within a group (Weilgart & Whitehead, 1997).;An analysis of the co-occurrence of codas and creaks was also performed with a preliminary examination of creak characteristics. Perhaps the most significant finding in this study relates to the duration of the creaks recorded at all three buoy recording locations. Overall, 98.9% of the creaks in this study had durations less than 4.0 s, an indication that they may be creaks associated with socializing and not foraging. Further support of the theory that much socialization activity was occurring during the present study came from the analysis of the co-occurrence of codas and creaks. Overall, 81.5% of all creaks produced, occurred in the presence of codas; vocalizations most often heard during socialization.;While the findings revealed herein may expand the knowledge base regarding coda repertoires and acoustic behavior of sperm whales in the NGoM, further research is called for to supplement the existing data in an effort to gain a better understanding of sperm whale vocal behavior during foraging, social, and other contexts in the NGoM.