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In 1990, a bottlenose dolphin was tracked for 25 days in Tampa Bay, Florida using a satellite-monitored Argos radio tag. The objectives for this pilot test for small inshore cetaceans were to: (1) determine the utility of the attachment, (2) examine the dolphin's movements, and (3) characterize the dolphin's dive behavior. This was the first time diel dive cycles of a bottlenose dolphin were demonstrated.
During a photoidentification study in the Bahamas (1994 and 1995), bottlenose dolphins were observed benthic-feeding. This newly described method of feeding, which involved the dolphin searching the sandy bottom, echolocating, and then diving headfirst into the sand, was termed ‘crater-feeding,' because of the crater made in the sand. Observers sometimes noted a fish in the dolphin's mouth as it came out of the sand. Video and photo documentation was used to record this behavior.
If you would like to learn more about this research, read following abstracts, or find the whole paper in the appropriate journal.
Satellite-monitored movements and dive behavior of a bottlenose dolphin (Tursiops truncatus) in Tampa Bay, Florida
Bruce R. Mate, Kelly A. Rossbach, Sharon L. Nieukirk, Randall S. Wells, A. Blair Irvine, Michael D. Scott and Andrew J. Read
Abstract: An adult, female bottlenose dolphin (Tursiops truncatus) was radio tagged and monitored via satellite-based Argos receivers for 25 d from 28 June to 23 July 1990, in Tampa Bay, Florida. A Total of 794 transmissions were obtained during 106 satellite passes. A mean of 3.9 (SE = 0.24) locations/day were determined by Service Argos and showed the animal remained in the bay, usually close to the southeastern shore. The dolphin moved at least 581 km at a minimum mean speed of 1.2 (SE =0.1) km/h. Data from 63,922 dives were recorded. The animal spent an average of 87.1 (SE = 0.6)% of the time submerged, with a mean dive duration of 25.8 (SE = 0.5) sec. Mean dive duration differed significantly between four periods of the day, as did the mean percent of time spent submerged. During the early morning the animal spent more time at the surface, averaged shorter dives, and was submerged less than other times of day. This is the first study to demonstrate diel dive cycles in a bottlenose dolphin. Four months after tag loss, the dolphin was photographed with no evidence of necrosis or disfigurement of the dorsal fin. Satellite telemetry was demonstrated as an effective means of documenting the movements and dive behavior of a small inshore cetacean.
Marine Mammal Science 11(4):452-463 (1995)
Underwater observations of benthic-feeding bottlenose dolphins (Tursiops truncatus) near Grand Bahama Island, Bahamas.
Rossbach, K. and D. Herzing
No abstract - Note
Marine Mammal Science 13(3):498-504 (1997).
Inshore and offshore bottlenose dolphin (Tursiops truncatus) communities distinguished by association patterns near Grand Bahama Island, Bahamas
Kelly A. Rossbach and Denise L. Herzing
Abstract: Little is known about the behavior of offshore dolphin populations. Our purpose was to distinguish and describe stable social groups of bottlenose dolphins (Tursiops truncatus) between inshore and offshore West End, Grand Bahama Island (26º42'N, 79º00'W). Photoidentification was conducted from May to September, 1994 to 1996. A simple ratio index described association patterns between dolphins. Multidimensional scaling of association indices (n = 1711 dolphin pairs) distinguished two dolphin communities consisting of 28 dolphins (19 of known sex) found inshore and 15 dolphins (12 of known sex) found ³27 km offshor e. Eight of the 15 offshore dolphins were opportunistically photographed in the same region between 1986 and 1990. The two communities were found at different water depths (Mann-Whitney U test, p< 0.01), over distinct bottom types (Kruska-Wallis test, p < 0.01), and used different bottom-foraging strategies. Long-term site fidelity of up to 10 years and repeated dolphin associations of up to 8 years occurred ³27 km from shore. Dolphins sighted ³15 times averaged 48 associates (SD = 11, n = 28). A dolphins' closest associate was of the same gender 74% of the time. This study is the first to report long-term site fidelity and association patterns of bottlenose dolphins found far from shore.
Canadian Journal of Zoology. 77:581-592 (1999).
Rossbach, K. (Accepted). Cooperative feeding among bottlenose dolphins (Tursiops truncatus) near Grand Bahama Island, Bahamas. Aquatic Mammals.