Diurnal Behavior of Dusky Dolphins, Lagenorhynchus obscurus, in Golfo Nuevo, Argentina

Degrati, Mariana; Dans, Silvana Laura; Pedraza, Susana N.; Crespo, Enrique A.; Garaffo, Griselda Valeria

doi:10.1644/07-mamm-a-110.1

Cited by 36 publications

(62 citation statements)

References 29 publications

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“…6), which would reduce the feeding time budget from 22 to 19%, at least during months when tour boats operated. It was also found that dolphins invested <11% of their time feeding during autumn (Degrati et al 2008), possibly representing a minimum threshold value. This seasonal variation should be taken into account if an extension of the dolphin-watching season is planned, since extension of the presence of boats into autumn could significantly reduce the overall feeding and socializing time budget.…”

Section: Discussionmentioning

confidence: 96%

“…Thus, the degree of anchovy patchiness may determine the time dolphins invest in traveling and searching for food as well as the time elapsing between 2 feeding events. Degrati et al (2008) found seasonal variation in time budgets while studying the activity pattern of dusky dolphins in the same area during a long period of time that included the whole autumn, following groups without commercial vessels in operation. They found that dolphins increased their traveling time but decreased their feeding time in autumn, and also suggested that this seasonal variation was related to a change in prey distribution and dolphin feeding strategy.…”

Section: Discussionmentioning

confidence: 97%

“…(Degrati et al 2008), and groups are distinctive enough in the field. The behavioral state was assigned by scan sampling (Altman 1974) before the boat approached the group, i.e.…”

Section: Methodsmentioning

confidence: 99%

“…In Argentina, dolphins contrastingly feed during daylight hours in smaller groups, on pelagic schooling fishes by means of a particular cooperative strategy (Würsig & Würsig 1980). Recently, it has been proposed that some traveling bouts could have a foraging function (Degrati et al 2008). These results suggest that feeding efficiency may be seriously affected by disturbance of behavioral sequences.…”

Section: Introductionmentioning

confidence: 99%

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Dusky dolphin and tourist interaction: effect on diurnal feeding behavior

Dans¹,

Crespo²,

Pedraza³

et al. 2008

Mar. Ecol. Prog. Ser.

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Dolphin watching is a relatively newly developed tourist activity. Although it is assumed to contribute to the conservation of marine ecosystems, its long-term adverse effects are still unknown. The present work aims to assess the impact of tour vessels on the behavior pattern of dusky dolphins displaying diurnal and cooperative feeding. We evaluated potential bias of commercial vessels to specific activities, short-term responses of dolphins to vessel approach, and longer-term effects of these changes, particularly on the activity budget and the time dolphins need to resume an activity. Several field experiments were carried out in which dolphins were approached by a research vessel or by commercial vessels. Group tracking was also made from a research vessel. Behavioral sequences were modeled by stochastic matrix models. Activity budget and time to return to an activity were obtained from matrix properties. Commercial trips found mostly feeding groups. Feeding showed the highest rate of change at the moment of vessel approach, and commercial vessels had an effect on the direction of change. Over the longer term, feeding and socializing time budgets decreased when commercial vessels were present. The time to return to feeding as well as the time it took for a group of dolphins to feed increased in the presence of commercial vessels. Dusky dolphins in South Atlantic waters feed during the day on patchily distributed prey. Our study demonstrates that boat presence negatively affects the longer-term feeding efficiency of dusky dolphins.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 97%

“…(Degrati et al 2008), and groups are distinctive enough in the field. The behavioral state was assigned by scan sampling (Altman 1974) before the boat approached the group, i.e.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dusky dolphin and tourist interaction: effect on diurnal feeding behavior

Dans¹,

Crespo²,

Pedraza³

et al. 2008

Mar. Ecol. Prog. Ser.

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“…Five categories of behavioural states were defined: milling, resting, travelling, feeding/foraging (hereafter foraging), and socializing as defined in previous studies (e.g. Norris & Dohl 1979, Bearzi 2005, Neumann & Orams 2006, Degrati et al 2008. Feeding was characterised by loose to disperse group formations, and dolphins were observed swimming in circles and pursuing fishes (prey observed at the surface).…”

Section: Methodsmentioning

confidence: 99%

Ecological niche segregation within a community of sympatric dolphins around a tropical island

Kiszka¹,

Simon-Bouhet²,

Martinez³

et al. 2011

Mar. Ecol. Prog. Ser.

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Investigating ecological segregation among organisms of a given community is challenging, especially when these organisms share similar patterns of distribution, and similar size and morphology. Around the island of Mayotte, a diversified community of at least 4 sympatric delphinids is present year round within a very restricted range: the Indo-Pacific bottlenose dolphin Tursiops aduncus, the spinner dolphin Stenella longirostris, the pantropical spotted dolphin S. attenuata, and the melon-headed whale Peponocephala electra. In addition, the Fraser's dolphin Lagenodelphis hosei makes temporary incursions into peri-insular waters as well. This study aims to assess niche segregation among this tropical dolphin community. We hypothesized that each species occupies its own distinct niche defined by the following axes: habitat, resources and time. We analysed habitat in relation to physiography, behavioural budgets and C and N stable isotope values from skin and blubber samples for each species. The results highlighted that habitat and behavioural budgets were relatively distinct among species, with few exceptions. However, in those species living on the outer reef slope where habitat and behaviour were not well discriminated, stable isotope analyses confirmed that species have different trophic levels (mostly reflected through δ 15 N values) or foraging habitat (mostly reflected through δ 13 C values). This study confirms that the use of multiple methodologies (habitat, behaviour and feeding ecology studies) help in discerning ecological niche segregation, especially when examining closely related species within a common restricted range. KEY WORDS: Tropical dolphins · Ecological niche · Habitats · Stable isotopes · Carbon · Nitrogen · South-west Indian Ocean · Mayotte Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 433: [273][274][275][276][277][278][279][280][281][282][283][284][285][286][287][288] 2011 will bring about competition between members of the same species (intra-specific competition) or between individuals of different species (inter-specific competition) (Roughgarden 1976). Intra-specific competition may be expressed by sex or age related difference in habitat and resource use and has consequences on social structures. Inter-species competition can take various forms, including direct interference (aggressive behaviour) and exploitation-competition, in which individuals indirectly compete for resources (Begon et al. 1986).Investigating segregation processes within communities of organisms that have similar size and morphology has been particularly challenging. In such communities, niche partitioning is difficult to assess as it can occur over small spatial and temporal scales. For example, in species with similar morphology (e.g. body size, jaw or beak shape, etc.), feeding niches are distinct even when feeding occurs in both species within the same area (MacArthur 1958). Niche segregation has been investigated in a number of top marine pred...

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Spatial genetic structure of dusky dolphin,Lagenorhynchus obscurus, along the argentine coast: preserve what scale?

Castro

Dans

Crespo

2015

Aquatic Conservation

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1. The dusky dolphin (Lagenorhynchus obscurus) represents one of the most abundant species of small cetacean in Argentine waters. During the 1980s and 1990s, high levels of incidental mortality in purse and trawl fisheries were documented, and in recent decades tourism activities have been added as a potential source of disturbance.2. The study objectives were to identify spatial genetic structure and regional genetic patterns of dusky dolphins along the Argentine coast. The variation of 413bp of the control region of 119 individuals over six locations spread along 2800 km (38°40'S to 54°30'S) was examined. Spatial genetic analyses, SAMOVA, genetic landscape shapes and autocorrelation analyses were conducted.3. The most probable configuration was K=2, island population vs. continental populations (F CT = 0.774) and the spatial autocorrelation analysis showed a strong regional genetic structure, defining an operational unit at < 50 km.4. The results provide valuable information that should be taken into account in the development of conservation strategies and management of the species; making the efforts focus on conserving vulnerable dusky dolphin groups by protecting their preferred coastal shallow habitat and by monitoring and regulating the dolphin watching and fishing activities, acting upon local populations along the Argentine coast.

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Diurnal Behavior of Dusky Dolphins, Lagenorhynchus obscurus, in Golfo Nuevo, Argentina

Cited by 36 publications

References 29 publications

Dusky dolphin and tourist interaction: effect on diurnal feeding behavior

Dusky dolphin and tourist interaction: effect on diurnal feeding behavior

Ecological niche segregation within a community of sympatric dolphins around a tropical island

Spatial genetic structure of dusky dolphin,Lagenorhynchus obscurus, along the argentine coast: preserve what scale?

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