Bottlenose Dolphin (<I>Tursiops truncatus</I>) Abundance, Site Fidelity, and Group Dynamics in the Marlborough Sounds, New Zealand

The Black Sea subspecies of the bottlenose dolphin (Tursiops truncatus ponticus) is threatened and has a small range. Its population structure is little known: it possibly includes a few local coastal populations. We assessed connectivity between coastal groupings in six localities along 800 km of the coastline based on records of photo-identified animals between 2004 and 2014. Abundance of these groupings, as estimated, ranged between 76 and 174 individually distinctive dolphins. In total, there were 350 identified individuals, of which 91 (26%) were resighted within the same areas. However, only three cases of individual movements between local coastal populations were recorded at the distances between 135 and 325 km. Therefore, despite the absence of physical barriers, the coastal Black Sea population is fragmented into numerous resident or locally migrating groupings with site fidelity. These local populations are loosely connected to each other with rare movements between them. This fragmentation can be a factor contributing to short-term fluctuations in abundance of Black Sea bottlenose dolphins and their decline in some localities, despite the potentially high population growth rate.

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Inshore and offshore bottlenose dolphin (Tursiops truncatus) communities distinguished by association patterns near Grand Bahama Island, Bahamas

Canadian Journal of Zoology ◽

10.1139/z99-018 ◽

1999 ◽

Vol 77 (4) ◽

pp. 581-592 ◽

Cited By ~ 17

Author(s):

Kelly A Rossbach ◽

Denise L Herzing

Keyword(s):

Bottlenose Dolphin ◽

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

Social Groups ◽

Foraging Strategies ◽

Association Patterns ◽

Simple Ratio ◽

Water Depths

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 (26°42'N, 79°00'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 greater than or equal to 27 km offshore. 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 (Kruskal-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 greater than or equal to 27 km from shore. Dolphins sighted greater than or equal to 15 times averaged 48 associates (SD = 11, n = 28). A dolphin's 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.

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