scholarly journals Social structure of a population of bottlenose dolphins (Tursiops truncatus) in the oceanic archipelago of Madeira, Portugal

2017 ◽  
Vol 98 (5) ◽  
pp. 1141-1149 ◽  
Author(s):  
Ana Dinis ◽  
Filipe Alves ◽  
Cátia Nicolau ◽  
Cláudia Ribeiro ◽  
Manfred Kaufmann ◽  
...  
Keyword(s):  
Social Structure ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Association Index ◽  
Photo Identification ◽  
Open Population ◽  
Time Period ◽  
Dolphin Population ◽  
Identification Analysis ◽  
Over Time

In order to investigate social structure, 11 years of individual photo-identification data of bottlenose dolphin were analysed. We examined the type of association indices between pairs of identified individuals; the patterns of affiliation between individual dolphins and the probabilities of association between individuals over time. Between 2001 and 2012, there were 272 encounters which resulted in the identification of 501 individuals. The discovery curve resulting from the photo-identification analysis indicated an open population with regular recruitment of new individuals. All individuals were found to be associated at an association index of <0.05. A total of 291 individuals recorded from 2004 to 2012 were used to assess the temporal pattern of the social structure. The model fit to the Standardized Lagged Association Rate (SLAR) that best described the studied bottlenose dolphin population was ‘casual acquaintances’, and the analysis of associations over time showed a decreasing SLAR curve that falls until reaching the null rate, confirming random associations. The decline of the SLAR curve after ~500 days (1.4 years) suggests disassociation over that time period which can be explained by demographic events such as mortality or emigration. In an open ocean habitat like Madeira this is not unexpected, as there are neither geographic boundaries nor enclosed environments. This population presented a dynamic and fluctuating social structure, where groups change in size and composition. In future conservation efforts this population should be considered as one large community, where individuals associate, disassociate and reassociate with each other over time.

scholarly journals The influence of fish farm activity on the social structure of the common bottlenose dolphin in Sardinia (Italy)

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10960
Author(s):  
Serena Frau ◽  
Fabio Ronchetti ◽  
Francesco Perretti ◽  
Alberto Addis ◽  
Giulia Ceccherelli ◽  
...  
Keyword(s):  
Social Structure ◽  
Bottlenose Dolphin ◽  
Foraging Strategy ◽  
Important Change ◽  
Fish Farm ◽  
Photo Identification ◽  
Common Bottlenose Dolphin ◽  
The Social ◽  
Dolphin Population ◽  
The Common

In a wide variety of habitats, including some heavily urbanised areas, the adaptability of populations of common bottlenose dolphin (Tursiops truncatus) may depend on the social structure dynamics. Nonetheless, the way in which these adaptations take place is still poorly understood. In the present study we applied photo-identification techniques to investigate the social structure of the common bottlenose dolphin population inhabiting the Gulf of Alghero (Sardinia, Italy), analysing data recorded from 2008 to 2019. The social structure analysis showed a division of the entire population into five different communities and the presence of non-random associations, while there was no evidence of segregation between sexes. Furthermore, results highlighted an important change in social structure through time, likely due to a reduction in fish farm activity since 2015. The division of the population into different communities, the presence of segregation based on the foraging strategy (inside or outside the fish farm area) and the social network measures were evaluated by analysing independently the two datasets: the intense and low farm activity periods: 2008–2014 and 2015–2020, respectively. Segregation among individuals belonging to the same foraging strategy class was found only in the earlier period, and the composition of the four communities was consistent with this result. Our study improves the knowledge about bottlenose dolphin adaptation, as a lower complexity in social structure was linked to a reduction in anthropogenic food availability.

Use of photo-identification data to quantify mother–calf association patterns in bottlenose dolphins

2003 ◽  
Vol 81 (8) ◽  
pp. 1421-1427 ◽  
Author(s):  
Kate Grellier ◽  
Philip S Hammond ◽  
Ben Wilson ◽  
Carol A Sanders-Reed ◽  
Paul M Thompson
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Small Population ◽  
Association Patterns ◽  
Photo Identification ◽  
Dolphin Population ◽  
The Mean ◽  
First Time

For social mammals living in fission–fusion societies, the mother–infant bond is long and extends beyond the nursing period. We successfully developed a technique, using photo-identification data, to quantify mother–calf association patterns in a small population of bottlenose dolphins, Tursiops truncatus, off eastern Scotland. By statistically comparing association indices between young calves and their associates we assigned 17 individual adults as mothers to 20 young calves with a 5% level of probability. The mean index of association between calves and mothers remained high until at least year 8 of life. While calves were still found in the same schools as their mother, they surfaced beside her less often as their age increased. This is the first time that the mother–calf bond has been quantitatively assessed for any bottlenose dolphin population inhabiting temperate waters. Results are compared with those from subtropical populations and are discussed with respect to the viability of this population.

scholarly journals Female reproductive output in a Mediterranean bottlenose dolphin Tursiops truncatus population

2020 ◽  
Vol 29 ◽  
pp. 123-136
Author(s):  
MF Blasi ◽  
C Bruno ◽  
L Boitani
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Reproductive Output ◽  
Bottlenose Dolphins ◽  
Reproductive Pattern ◽  
Photo Identification ◽  
Conservation Actions ◽  
Dolphin Population ◽  
The Mean ◽  
June July

The reproductive output of wild bottlenose dolphins Tursiops truncatus has extensively been investigated; nevertheless, it remains widely unexplored in the Mediterranean Sea. We investigated the reproductive history of female bottlenose dolphins in the Aeolian Archipelago (Italy). Thirteen years of photo-identification data were used to track the reproductive pattern of 7 females and their 16 calves. The birth period was accurately estimated within 1 mo for 6 calves (37.5%), peaking in June/July. The mean number of calves for females was 2.3 ± 1.1 (SD), ranging from 1 to 4. The mean interbirth interval was 3.5 ± 1.6 yr, ranging from 2 to 7 yr. The mean weaning age was 3.2 ± 0.6 yr, although 1 calf may have been weaned as late as its fifth birthday. Mother-calf postweaning associations were tracked for 9 calves and ranged from 4 to 10 yr of residence in the maternal group of the calf. The age of first pregnancy was 7.5 yr. The number of calves was influenced by the mean maternal group size, with females that were sighted in larger groups having more calves. However, the number of calves was not influenced by the strength of the associations of mothers with other females. Calf mortality by age 1 was high (12.5%). Two juveniles also died postweaning within 6 yr of their birth. Finally, 2 females may have died during the study, as they were not re-sighted at the end of the study. Our results highlight the need to implement urgent conservation actions to protect this bottlenose dolphin population.

scholarly journals On the behaviour of an under-studied population of bottlenose dolphins in the Southern Adriatic Sea

2018 ◽  
Vol 99 (4) ◽  
pp. 1017-1023 ◽  
Author(s):  
Flavio Affinito ◽  
Cristobal Olaya Meza ◽  
Aylin Akkaya Bas ◽  
Deborah Brill ◽  
Guy Whittaker ◽  
...  
Keyword(s):  
Group Size ◽  
Bottlenose Dolphin ◽  
Adriatic Sea ◽  
Bottlenose Dolphins ◽  
Anthropogenic Pressure ◽  
Social Predictors ◽  
Dolphin Population ◽  
Autumn And Winter ◽  
Effective Conservation ◽  
Study Monitoring

AbstractPerhaps the world's best-known cetacean, the bottlenose dolphin shows considerable variation in behaviour between and within populations in relation to differences in natural and anthropogenic conditions. Drivers of behavioural variation need to be identified to understand the dynamics of wild dolphin populations. Little research has been published on the bottlenose dolphin population found in the Southern Adriatic Sea. Using a set of spatial, temporal and social predictors, we aimed to investigate what variables are related to the behaviour of an under-studied population of bottlenose dolphins along the coastline of Montenegro. We present the results of a year-long study monitoring the behaviour of bottlenose dolphins along coastal Montenegro. We considered the effect of topography, seasonality and group size. A large proportion of travelling (55%) small groups (mean 4, range 1–9) in shallow waters (<50 m) was observed. We showed that seasonality alone explained behaviour best, with surface-feeding and socializing-resting increasing in autumn and winter. Group size was found to be a result of behavioural choice. We suggest seasonal changes in environmental conditions and anthropogenic pressure may explain the recorded behavioural pattern. This research points to the necessity of increased collaboration in the region to help understand complex patterns in behaviour and habitat use of local dolphin populations if effective conservation measures are to be developed.

scholarly journals Genetic relatedness delineates the social structure of southern Australian bottlenose dolphins

2019 ◽  
Vol 30 (4) ◽  
pp. 948-959 ◽  
Author(s):  
Fernando Diaz-Aguirre ◽  
Guido J Parra ◽  
Cecilia Passadore ◽  
Luciana Möller
Keyword(s):  
Social Structure ◽  
Genetic Relatedness ◽  
Social Systems ◽  
Bottlenose Dolphins ◽  
South Australia ◽  
Intrinsic Factors ◽  
Photo Identification ◽  
The Social ◽  
Modularity Analysis ◽  
Network Metrics

AbstractSocial relationships represent an adaptive behavioral strategy that can provide fitness benefits to individuals. Within mammalian societies, delphinids are known to form diverse grouping patterns and show a variety of social systems. However, how ecological and intrinsic factors have shaped the evolution of such diverse societies is still not well understood. In this study, we used photo-identification data and biopsy samples collected between March 2013 and October 2015 in Coffin Bay, a heterogeneous environment in South Australia, to investigate the social structure of southern Australian bottlenose dolphins (Tursiops cf. australis). Based on the data from 657 groups of dolphins, we used generalized affiliation indices, and applied social network and modularity methods to study affiliation patterns among individuals and investigate the potential presence of social communities within the population. In addition, we investigated genetic relatedness and kinship relationships within and between the communities identified. Modularity analysis revealed that the Coffin Bay population is structured into 2 similar sized, mixed-sex communities which differed in ranging patterns, affiliation levels and network metrics. Lagged association rates also indicated that nonrandom affiliations persisted over the study period. The genetic analyses suggested that there was higher relatedness, and a higher proportion of inferred full-sibs and half-sibs, within than between communities. We propose that differences in environmental conditions between the bays and kinship relationships are important factors contributing to the delineation and maintenance of this social structure.

The distribution, abundance and group dynamics of Indian Ocean humpback dolphins (Sousa plumbea) in the Emirate of Abu Dhabi (UAE)

2017 ◽  
Vol 98 (5) ◽  
pp. 1119-1127 ◽  
Author(s):  
Bruno Díaz López ◽  
Edwin Grandcourt ◽  
Séverine Methion ◽  
Himansu Das ◽  
Ibrahim Bugla ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Group Dynamics ◽  
Human Impacts ◽  
Conservation Status ◽  
Arabian Gulf ◽  
Abu Dhabi ◽  
Photo Identification ◽  
Open Population ◽  
Dolphin Population ◽  
Near Shore

The Arabian Gulf is one of the most heavily impacted water bodies raising serious concerns about the conservation status of many marine species. A limited coastal range and near-shore distribution make Indian Ocean humpback dolphins particularly vulnerable to mortality and traumatic injuries from heavy maritime traffic and gill-netting practices. Prior to the present study, no research had focused on the ecology of this species in the Arabian Gulf, despite the potential for human impacts. The mark–recapture method of photo-identification, undertaken during 55 boat-based surveys conducted between 2014 and 2015, was used to assess the occurrence, abundance and use of habitat of this endangered species along the coast of the Emirate of Abu Dhabi (UAE). In all, 368 h and 6703 km of observation were carried out over a period of 5 months, and 54 encounters were made with humpback dolphins. The group size ranged from 1 to 24 individuals and group composition showed that 79% of the observed dolphins were adults. Abundance estimates were calculated and fitted with open population models. A review of all available data indicates that the studied population is the largest reported in the world with 701 (95% CI = 473–845) individuals. While their occurrence within Abu Dhabi near-shore waters is frequent, the survey area appears to be only a part of a much larger home range for this humpback dolphin population. The observation of multiple threats derived from anthropogenic activities increases our concerns regarding the conservation of this important dolphin population.

Using blubber biopsies to provide ecological information about bottlenose dolphins (Tursiops truncatus) around the Azores

2007 ◽  
Vol 87 (1) ◽  
pp. 223-230 ◽  
Author(s):  
M.J. Walton ◽  
M.A. Silva ◽  
S.M. Magalhães ◽  
R. Prieto ◽  
R.S. Santos
Keyword(s):  
Fatty Acid ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Fatty Acid Profiles ◽  
The Bahamas ◽  
Azores Archipelago ◽  
Photo Identification ◽  
Ecological Information ◽  
Island Group

Fatty acid profiles were used to investigate aspects of bottlenose dolphin populations around the Azores archipelago. Biopsy samples were obtained from 70 dolphins during the period 2002–2004. No statistically significant differences in profiles were found between different island groups, between sexes or between year of sampling. Thus no evidence was seen for island group fidelity, in contrast to bottlenose dolphins found around similar island groups such as the Hawaiian archipelago or the Bahamas. The findings are consistent with concurrent genetic and photo-identification studies on dolphins in the Azores.

Bottlenose dolphin (Tursiops truncatus) presence and incidental capture in a marine fish farm on the north-eastern coast of Sardinia (Italy)

2007 ◽  
Vol 87 (1) ◽  
pp. 113-117 ◽  
Author(s):  
Bruno Díaz López ◽  
Julia Andrea Bernal Shirai
Keyword(s):  
Marine Fish ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Fish Farm ◽  
Eastern Coast ◽  
Encounter Rate ◽  
Photo Identification ◽  
Incidental Capture ◽  
The North ◽  
North Eastern

On the north-eastern coast of Sardinia, from November 2004 to January 2006, the first attempt in the Mediterranean basin to obtain information on encounter rate, group size and incidental capture of bottlenose dolphins in a marine fish farm was assessed, combining direct observations from fish farm boats with photo-identification studies. During 15 months of research, 79 d (65.3% of the total monitored days) were spent in direct observation of 146 groups of bottlenose dolphins around the fish farm cages. There was a peak in bottlenose dolphin presence during winter. Photographs were taken in the fish farm area during 79 encounters on 61 different days (totalling 34 marked individuals). The regular occurrence of some dolphins suggests individual preferences for the fish farm area. The incidental bottlenose dolphin capture observed in large, loose predator nets (1 dolphin per month) is cause for concern, as it is questionable whether or not the bottlenose dolphins in the area can sustain incidental capture of this magnitude. The information gained from this study shows the necessity for further regulations to be established, both in the use of predator nets and management of marine fish farms.

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

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.

Presenting vertebral deformities in bottlenose dolphin Tursiops truncatus calves from a protected population in northeast Scotland

2020 ◽  
Vol 140 ◽  
pp. 103-108
Author(s):  
KP Robinson ◽  
GN Haskins ◽  
SM Eisfeld-Pierantonio ◽  
T Sidiropoulos ◽  
CCG Bamford
Keyword(s):  
North Sea ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Maternal Separation ◽  
Well Being ◽  
Early Age ◽  
Photo Identification ◽  
Causative Factors ◽  
Moray Firth ◽  
Dolphin Population

Photographs collected during a 23 yr photo-identification study in the Moray Firth were examined to assess the prevalence, type and severity of vertebral deformations present in bottlenose dolphin Tursiops truncatus calves. Fifteen cases of presenting spinal anomalies (scoliosis, kyphosis, lordosis and combinations thereof) of variable severity were identified in 7.4% of all known calves from the population. Thirteen of the 15 anomalies were either manifest from birth or acquired from an early age, as ascertained from longitudinal sightings histories of their mothers. Most afflicted calves died during early development or shortly after maternal separation. However, 3 survived to adulthood and persist in the population to date, in addition to 2 dependent infants whose fate remains to be established. At 15+ yr of age, the oldest surviving individual was remarkably one of the most severe cases identified, highlighting the ability of these delphinids for adaptation to such gross structural deformities. The aetiology of the observed conditions could be attributed to a range of causative factors that may have implications for the well-being and health of this North Sea coastal dolphin population, a topic which merits further investigation.

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