Photographic Identification Of Individual Fin Whales Balaenoptera Physalus In The Gulf Of Maine

Author : William Richard Cioffi
Publisher :
ISBN 13 :
Total Pages : 208 pages
Book Rating : 4.:/5 (17 download)

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Download or read book Fin Whale (Balaenoptera Physalus) Associations on a Feeding Ground in the Western Gulf of Maine written by William Richard Cioffi and published by . This book was released on 2015 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fin whales (Balaenoptra physalus) are commonly considered solitary mammals and are not found in stable groups. Transient associations are observed on the feeding grounds in the western Gulf of Maine. These associations consist of animals coordinating their movements in close physical proximity and sometimes feeding is observed in these groups. Group size ranges from 2 to 10, through larger groups are less stable. Recent research suggests there may be age and sex related effects on similar associations in a closely related species, the humpback whale, Megaptera novaeangliae (Ramp et al., 2010). The purpose of this work is to investigate the structure and function of fin whale associations. Data on individually identified fin whales was collected from 2005-2009 opportunistically on whale watching boats in New Hampshire and Massachusetts. Photo-identification was used to match whales in this study with whales seen at other locations around the Gulf of Maine and where possible sex data was determined from filed observations or biopsies conducted by DenDanto (1998). Spatial distribution of groups, preferred associates, sexual makeup of groups, diel patterns to grouping, and behavior of singles and groups were all investigated. Additionally, a potential methodology for determining prey abundance by measuring surface copepod density was attempted. The spatial distribution of associated fin whales was not significantly predicted by bathymetry in a generalized additive model, while that of non-associated whales was significantly predicted. Since bathymetry should be related to prey density, this result indicates that associations may serve non-feeding functions. These other functions may include male-male competition or courtship of potential mates. No preferred associates were detected among individual identified fin whales. Large differences in gregariousness among individuals were detected. These are possible due to a sexual bias in groups. Males were found to be overrepresented in associations during the summer. When both sexes were known in a 2 whale association, male-male groups were most common, followed by male-female groups and female-female groups. There was no significant difference in male and female participation in associations in the fall. This suggests that females may incur a cost from grouping with males during the summer, but may permit grouping in the fall, perhaps for reproductive purposes. Costs for females may include harassment from males or inability to cooperatively feed because of different diet requirements. Additionally, since baleen whale males are smaller than females, their lower energetic requirements may allow them more time for social behaviors either and account for their increased participation in grouping. Diel patterns in grouping were also detected in the summer, but not in the fall, possibly pointing to a change in prey, or a change in the function of some groups in the fall perhaps toward breeding activities. While ventilation rate, ventilation to diving ratio, and speed were not significantly different for single whales and groups of fin whales, some observations suggested that groups of whales engage in social behaviors not related to feeding. This study suggests the possibility that fin whale feeding habitat in the western Gulf of Maine may also be important habitat for breeding activities. Further studies could test for differences in the function of associations based on sex composition using acoustic data along with real time behavioral sampling and a careful definition of association. Since little is known about fin whale breeding behavior and migration patterns, this line of research is essential to developing effective management plans for an endangered cetacean species.