Temporal patterns and types of sperm whale (Physeter macrocephalus) codas in the Northern Gulf of Mexico: a metadata analysis

• Main Author: Apple, Trent Curtis
• Format: Thesis
• Language: English
• Published: Texas A&M University 2002
• Subjects: wildlife and fisheries sciences; Major wildlife and fisheries sciences; Physeter macrocephalus; Sperm whale
• Online Access: http://hdl.handle.net/1969.1/ETD-TAMU-2002-THESIS-A65

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [e-mail], referencing the URI of the item. Includes bibliographical references (leaves 107-116). Issued also on microfiche from Lange Micrographics. Variation in sperm whale codas, short rhythmic series of clicks, was examined across annual, seasonal, and time-of-day temporal categories. Recordings were made from towed linear arrays during two-week seasonal cruises of the Northern Gulf of Mexico (NGOM) spanning May 1992 - August 1994 and October 1996 - August 1997. Archived sperm whale vocalizations were randomly sampled posthoc and codas were classified by the number and temporal pattern of their clicks: Short ([] 5 clicks) versus Long ([] 6 clicks), as well as Regular (equally-spaced clicks), Variable (unevenly-spaced clicks), and Plus-one (double intervals between the last two clicks). A total of 842 codas were analyzed, comprising 17 different coda types. The high number of Regular codas across all years and the lack of consistently significant temporal variation in codas suggest that a resident population of animals inhabits the NGOM. The high percentage of shared coda types between the Caribbean and NGOM may indicate movement of whales between these two regions. More codas (predominantly Long and Variable) were heard during 1996, compared to a greater diversity of coda types during 1997. In 1996, cows and calves were aggregated near the Mouth of the Mississippi River (MOM) and in 1997, whales were found in loose associations over DeSoto Canyon and in the presence of dolphins. More Plus-one codas were found during Spring than Fall, as were more Regular and Short codas recorded in Summer than Fall. During Spring, groups were concentrated near the MOM, and in Summer whales were sparsely distributed across broad areas. High diversity of coda types as well as the abundance of Long and Variable codas is likely related to crepuscular peaks observed in foraging activity and a three-hour cycle associated with deep diving. The proximate differences observed between temporal scales may be attributed to variation in oceanographic conditions affecting the spatial distribution and abundance of sperm whales as well as to contextual differences in behavior. Further research involving more acoustic data as well as comparisons with photo-identification, genetic, and behavioral information are needed to further corroborate the variation observed.