Group Characteristics, Site Fidelity And Seasonal Abundance Of Bottlenosed Dolphins (Tursiops Aduncus) In Jervis Bay And Port Stephens, South-Eastern Australia

Social organisation and abundance of bottlenose dolphins (Tursiops aduncus) in Jervis Bay (JB) and Port Stephens (PS), NSW, were investigated through behavioural/photo-identification surveys between May 1997 and April 2000. Mean group size was significantly larger at JB (12.3 � 0.87, n =167) compared to PS (6.8 � 0.37, n = 218). At both sites, groups were significantly larger when calves were present. Group size varied with activity, being smallest when feeding and largest when socialising. While mean group size of feeding dolphins did not vary between sites, travelling and socialising groups were significantly larger in JB. Site fidelity was assigned based on sighting rates and presence across seasons. Sighting rates varied significantly between areas, but the proportion of dolphins categorised as residents, occasional visitors and transients did not. Minimum abundance by season, based on mark-resighting of recognisable individuals, ranged from 61 � 3.2 to 108 � 7.1 in JB and 143 � 8.1 to 160 � 8.1 in PS. Differences in group size at the two sites may relate to social factors and/or human impacts, while differences in abundance may be associated with habitat size and complexity. The lack of dolphin matches between areas suggests that they represent distinct populations.

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Patterns of association among female Indo-Pacific bottlenose dolphins (Tursiops aduncus) in a population forming large groups

Behaviour ◽

10.1163/1568539x-00003453 ◽

2017 ◽

Vol 154 (9-10) ◽

pp. 1013-1028 ◽

Cited By ~ 1

Author(s):

Miki Nishita ◽

Miki Shirakihara ◽

Masao Amano

Keyword(s):

Group Size ◽

Bottlenose Dolphins ◽

Reproductive Status ◽

Association Measure ◽

Remarkable Feature ◽

Tursiops Aduncus ◽

Large Group ◽

Photo Identification ◽

Factors Influencing ◽

Large Groups

Indo-Pacific bottlenose dolphins (Tursiops aduncus) around Amakusa-Shimoshima, Japan form large groups of >100 individuals, a remarkable feature of this population, which is much larger than previously studied bottlenose dolphins. Using photo-identification data collected on 33 days in 2012, associations among 70 females were investigated using two scales of association measure (photograph- and group-based association) to know whether they associate based on their reproductive status, as is typically observed in other populations with smaller group size. Significant differences in associations between females of the same reproductive status category and those in different categories were detected, and a female that lost her calf within a year decreased associations with females with calves of the same age. These suggests that even in a population with large group size, the reproductive status of females is one of the factors influencing their associations.

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Seasonal Abundance and Site Fidelity of Bottlenose Dolphins (Tursiops truncatus) in Mississippi Sound

Aquatic Mammals ◽

10.1578/am.30.2.2004.299 ◽

2004 ◽

Vol 30 (2) ◽

pp. 299-310 ◽

Cited By ~ 24

Author(s):

Carrie W. Hubard ◽

Kathy Maze-Foley ◽

Keith D. Mullin ◽

William W. Schroeder

Keyword(s):

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

Seasonal Abundance ◽

Mississippi Sound

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Capitoline Dolphins: Residency Patterns and Abundance Estimate of Tursiops truncatus at the Tiber River Estuary (Mediterranean Sea)

Biology ◽

10.3390/biology10040275 ◽

2021 ◽

Vol 10 (4) ◽

pp. 275

Author(s):

Daniela Silvia Pace ◽

Chiara Di Marco ◽

Giancarlo Giacomini ◽

Sara Ferri ◽

Margherita Silvestri ◽

...

Keyword(s):

Population Size ◽

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

River Estuary ◽

Suitable Habitat ◽

Tyrrhenian Sea ◽

Abundance Estimate ◽

Photo Identification ◽

Tiber River

Periodic assessments of population status and trends to detect natural influences and human effects on coastal dolphin are often limited by lack of baseline information. Here, we investigated for the first time the site-fidelity patterns and estimated the population size of bottlenose dolphins (Tursiops truncatus) at the Tiber River estuary (central Mediterranean, Tyrrhenian Sea, Rome, Italy) between 2017 and 2020. We used photo-identification data and site-fidelity metrics to study the tendency of dolphins to remain in, or return to, the study area, and capture–recapture models to estimate the population abundance. In all, 347 unique individuals were identified. The hierarchical cluster analysis highlighted 3 clusters, labeled resident (individuals encountered at least five times, in three different months, over three distinct years; n = 42), part-time (individuals encountered at least on two occasions in a month, in at least two different years; n = 73), and transient (individuals encountered on more than one occasion, in more than 1 month, none of them in more than 1 year; n = 232), each characterized by site-fidelity metrics. Open POPAN modeling estimated a population size of 529 individuals (95% CI: 456–614), showing that the Capitoline (Roman) coastal area and nearby regions surrounding the Tiber River estuary represent an important, suitable habitat for bottlenose dolphins, despite their proximity to one of the major urban centers in the world (the city of Rome). Given the high number of individuals in the area and the presence of resident individuals with strong site fidelity, we suggest that conservation plans should not be focused only close to the Tiber River mouths but extended to cover a broader scale of area.

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Ecology and comparison of coastal and offshore bottlenose dolphins (Tursiops truncatus) in California

Marine and Freshwater Research ◽

10.1071/mf08279 ◽

2009 ◽

Vol 60 (6) ◽

pp. 584 ◽

Cited By ~ 18

Author(s):

Maddalena Bearzi ◽

Charles A. Saylan ◽

Alice Hwang

Keyword(s):

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

Photo Identification ◽

Santa Monica Bay ◽

Santa Monica ◽

Inshore Waters

Populations of coastal and offshore bottlenose dolphins (Tursiops truncatus) are considered to differ ecologically, with implications for their protection and management. We assessed occurrence, distribution and behaviour of coastal and offshore populations of dolphins during a photo-identification study in Santa Monica Bay and nearby areas (1997–2007). Bottlenose dolphins occurred year-round and were encountered on 44.2% of all surveys (n = 425). We photo-identified 647 individuals; of these, 375 (58.0%) were coastal (<1 km from shore), 241 (37.2%) offshore (1–65 km from shore) and 31 were both (4.8%). Dolphins mostly travel (69.0%) and travel-dive (61.5%), with offshore dolphins socialising more (22.6%) than coastal. There were low re-sighting rates for both coastal and offshore dolphins. Low re-sighting rates of coastal individuals provide little evidence of year-round site fidelity, suggesting their range is greater than the study area. Several individuals were re-sighted between and over 1-year periods, often foraging. This suggests that coastal dolphins: (1) are highly mobile within inshore waters, but spend time foraging in the study area, and (2) range >1 km from shore, contrary to what has been previously reported.

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Abundance estimate and seasonal patterns of grey seal (Halichoerus grypus) occurrence in Brittany, France, as assessed by photo-identification and capture–mark–recapture

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315407054586 ◽

2007 ◽

Vol 87 (1) ◽

pp. 365-372 ◽

Cited By ~ 13

Author(s):

Maureen Gerondeau ◽

Christophe Barbraud ◽

Vincent Ridoux ◽

Cécile Vincent

Keyword(s):

Breeding Season ◽

Site Fidelity ◽

Seasonal Abundance ◽

Breeding Period ◽

Home Ranges ◽

Grey Seal ◽

British Isles ◽

Mark Recapture ◽

Abundance Estimate ◽

Photo Identification

It has been suggested that the large grey seal colonies around the British Isles form local populations within a metapopulation, and that seal movements outside the breeding season lead to considerable overlap between individual home ranges. Individual behaviour and population dynamics of small peripheral colonies may also play a role in the metapopulation. We studied the French grey seal colony of the Molène archipelago, at the southern-most limit of the species' range. We analysed photo-identification data with capture–mark–recapture techniques in order to estimate the total seasonal abundance of grey seals in the archipelago and to quantify the seasonal rates of occurrence or movements of male and female seals. We found that between 58 (95% confidence interval: 48–71) and 98 (95% CI: 75–175) individuals hauled out in the archipelago during the summers of 1999 and 2000. The use of multistate models allowed the assessment of seasonal site fidelity and indicated that it varied between key periods of the annual cycle, particularly for females. Males showed a constant fidelity rate of 56% from one season to another. Hence, even though they showed high inter-annual site fidelity, they did not seem to have a preferred season for using the archipelago. On the contrary, female grey seals showed the highest site fidelity between moult and summer (around 80%), and the lowest fidelity between summer and the breeding period (34–43%). Thus, females seem to use the Molène archipelago preferentially in summer and leave the site before the breeding season, which explains the very low local pup production. Philopatry may explain this pre-breeding emigration, and we suggest that most grey seals observed in the Molène archipelago were born and breed in other local breeding populations, probably the south-western British Isles.

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Strong site-fidelity increases vulnerability of common bottlenose dolphins Tursiops truncatus in a mass tourism destination in the western Mediterranean Sea

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315413000866 ◽

2013 ◽

Vol 94 (6) ◽

pp. 1227-1235 ◽

Cited By ~ 8

Author(s):

Joan Gonzalvo ◽

Jaume Forcada ◽

Esteve Grau ◽

Alex Aguilar

Keyword(s):

Site Fidelity ◽

Bottlenose Dolphins ◽

Local Population ◽

Western Mediterranean ◽

Marine Biodiversity ◽

Tourism Destination ◽

Photo Identification ◽

Mass Tourism ◽

Management Actions ◽

Common Bottlenose Dolphin

The local population of common bottlenose dolphin in the Balearic Islands coastal waters, a mass tourism destination in the western Mediterranean subject to increasing anthropogenic pressures, was monitored over a three-year period. Photo-identification surveys provided a relatively small population estimate, even though the islands are considered to be a hotspot for the species in the Mediterranean. Dolphins showed strong site-fidelity and relatively limited mobility across the archipelago, which makes them highly dependent on waters which are severely affected by overfishing, habitat degradation and boat disturbance resulting from a continuously-growing tourism and shipping industry. Ecosystem-based management actions are urgently needed to ensure the conservation of this fragile population of bottlenose dolphins. Conservation measures should be developed within the already-existing political and legal marine biodiversity conservation framework and in collaboration with local authorities and stakeholders.

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Estimates of abundance and change in abundance of the Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

10.1101/2019.12.13.875179 ◽

2019 ◽

Author(s):

OA Vargas-Fonseca ◽

SP Kirkman ◽

WC Oosthuizen ◽

T Bouveroux ◽

V Cockcroft ◽

...

Keyword(s):

South Africa ◽

Conservation Status ◽

Bottlenose Dolphins ◽

South Coast ◽

The South ◽

Model Estimate ◽

Entire Study ◽

Tursiops Aduncus ◽

Photo Identification ◽

Open Population

AbstractWe investigated the abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa, from the Goukamma Marine Protected Area (MPA) to the Tsitsikamma MPA, between 2014 and 2016. During this period, 662.3h of boat-based photo-identification survey effort was carried out, and the sighting histories of 817 identified individuals were used to estimate abundance using mark-recapture modelling. The selected open population model (POPAN) provided an estimate of 2,295 individuals (95% CI: 1,157-4,553) for the entire study area. A model estimate was produced for a subset of the study area, Plettenberg Bay, which could be compared with a past estimate for this location (2002-2003). The comparison suggested a 72.3% decrease in abundance, from 6,997 (95% CI: 5,230-9,492) in 2002-2003 to 1,940 (95% CI: 1,448-2,600) in 2014-2016. The decline in abundance was supported by a 72% reduction in mean group size for Plettenberg Bay between the periods. It is essential to be able to assess abundance changes at other locations to inform revision of T. aduncus conservation status in South Africa.

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Long-term site fidelity and residency patterns of bottlenose dolphins (Tursiops truncatus) in the Tramandaí Estuary, southern Brazil

Latin American Journal of Aquatic Mammals ◽

10.5597/00224 ◽

2017 ◽

Vol 11 (1-2) ◽

pp. 155-161 ◽

Cited By ~ 7

Author(s):

Amanda Baron Di Giacomo ◽

Paulo Henrique Ott

Keyword(s):

Tursiops Truncatus ◽

Site Fidelity ◽

Bottlenose Dolphins ◽

Southern Brazil ◽

Local Conservation ◽

Entire Study ◽

Photo Identification ◽

Average Observation ◽

Number Of Individuals

The occurrence of common bottlenose dolphins (Tursiops truncatus) in Tramandaí Estuary, southern Brazil, is described based on a photo-identification study conducted between January 2009 and February 2010. A total of 128 survey days were conducted with an average observation effort of 2.6 hours per day (SD = 0.6). Approximately 2050 photographs were taken from a shore land location at the mouth of the estuary. A total of nine dolphins were identified, including three calves. The dolphins were observed during all seasons, with a greater frequency during fall (79.3% of the days) and winter (60.7% of the days). The summer presented the lowest occurrence (2.4% of the days) of dolphins. During the entire study period, the maximum number of individuals sighted in any given day ranged from one to seven (average = 2.8 dolphins; SD = 1.35; n = 51). The residence indices, based on the resighting frequency of dolphins during the study period, ranged from 0.02 to 0.24 (average = 0.13; SD = 0.08; n = 9). However, most of the animals (67%) were resighted in over five months during a year and could be classified as residents. Longterm site fidelity was detected by resightings of four dolphins for over 18 years. These data combined reinforce the importance of the Tramandaí Estuary for the common bottlenose dolphins in the region and highlight the need for local conservation efforts to guarantee the long-term persistence of these coastal populations.

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