Marine vessels alter the behaviour of bottlenose dolphins Tursiops truncatus in the Istanbul Strait, Turkey

Bas, AA; Christiansen, Fredrik; Öztürk, Bayram; Öztürk, AA; Ma, An; Watson, L. Cynthia

doi:10.3354/esr00836

Cited by 23 publications

(23 citation statements)

References 42 publications

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“…Moreover, Montenegro's economy relies heavily on tourism, with the peak season taking place in warmer months where boat traffic increases dramatically and high-speed loud boats such as jet skis are encountered on a regular basis (personal observations). Increases in boat traffic have been linked to a decrease in foraging and socializing behaviours in bottlenose dolphins in the Mediterranean (Papale et al, 2012;Bas et al, 2017) and elsewhere (Nowacek et al, 2001;Bejder et al, 2006). In fact, socializing and resting are the most sensitive behaviours to human disturbance (Lusseau & Higham, 2004).…”

Section: Discussionmentioning

confidence: 99%

“…Due to the species’ predominantly coastal range, this decline is often attributed to anthropogenic factors (Wilson et al ., 1997). Behavioural changes are associated with a combination of environmental cues and human pressures that can lead to changes in population-level dynamics (Nowacek et al ., 2001; Bas et al ., 2017). It is therefore important that we understand natural patterns of dolphin behaviour so any anthropogenic impacts can be mapped and quantified (Bearzi, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Bathymetry contours show 25 m increases in depth (data from: IOC, IHO & BODC, 1994). Ethogram of T. truncatus behaviour based on previous studies:Lusseau (2003) andBas et al (2017)…”

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confidence: 99%

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

et al. 2018

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Perhaps 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.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…In other words, the lack of Lombard response was an acoustic avoidance response to the presence of the vessel. The physical presence of the vessel has been shown to reduce bottlenose dolphin [37] and humpback whale [38] foraging activity as well as bottlenose dolphin resting and socializing behaviour [37]. Other studies, carried out on this population of humpback whales at this study site, found that humpback whale groups significantly changed their migration speed and direction to avoid a slowly (4 knots) moving vessel towing (silent) air gun arrays [39,40].…”

Section: Discussionmentioning

confidence: 95%

The effects of vessel noise on the communication network of humpback whales

Dunlop

2019

R. Soc. open sci.

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Humpback whales rely on acoustic communication to mediate social interactions. The distance to which these social signals propagate from the signaller defines its communication space, and therefore communication network (number of potential receivers). As humpback whales migrate along populated coastlines, they are likely to encounter noise from vessel traffic which will mask their social signals. Since no empirical data exist on baleen whale hearing, the consequences of this are usually assumed, being the modelled reduction in their communication space. Here, the communication space and network of migrating humpback whales was compared in increasing wind-dominated and vessel-dominated noise. Behavioural data on their social interactions were then used to inform these models. In typical wind noise, a signaller's communication space was estimated to extend to 4 km, which agreed with the maximum separation distance between groups that socially interacted. An increase in vessel noise reduced the modelled communication area, along with a significant reduction in group social interactions, probably due to a reduction in their communication network. However, signal masking did not fully explain this change in social behaviour, implying there was also an additional effect of the physical presence of the vessel on signaller and receiver behaviour. Though these observed changes in communication space and social behaviour were likely to be short term and localized, an increase in vessel activity due to tourism and coastal population growth may cause more sustained changes along the humpback whale migration paths.

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“…Bottlenose dolphins have been the focus of various studies in the Istanbul Strait since the early 1900s (Deveciyan, 1926;Çelikkale et al, 1988;Öztürk, 1996;Öztürk & Öztürk, 1996Öztürk et al, 2009;Baş et al, 2015;Bas et al, 2017aBas et al, , 2017b). Yet only a handful of studies have touched on the topic of habitat use (Dede, 1999;Öztürk et al, 2009;Altuğ et al, 2011;Ryan et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Encounter rate, residency pattern and site fidelity of bottlenose dolphins (Tursiops truncatus) within the Istanbul Strait, Turkey

Bas

Öztürk

2018

J. Mar. Biol. Ass.

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The Istanbul Strait is an important cetacean habitat that is intensely used by humans. Yet little is known about their spatial-temporal distribution. To understand the encounter rates and residency patterns of bottlenose dolphins, photo-identification data were collected between 2011 and 2016 in the Istanbul Strait. The study showed that bottlenose dolphins are a regular, year-round component of the strait. The encounter rate was estimated to be four groups (22 individuals) per 10 km. The adjacent waters of Marmara Sea and Black Sea, that host relatively less marine traffic, had the highest number of encounters in the area. Conversely, the middle sections had the lowest number of encounters but the highest marine vessel density. Further, the encounter rates dropped to zero in the fishing zones, where the number of purse seines reached up to 100 per day. Additionally, dolphins showed varying degrees of residency patterns, with multi-year re-sightings. Maximum re-sighting distance was up to 35 km, which is more than the total length of the strait. This movement pattern should be investigated as it might reveal possible migration between local populations. This study finds that the Istanbul Strait serves as a critical habitat for the regional bottlenose dolphin populations and they are likely to be a part of a resident local population with a home range extending the length of the strait. Dedicated surveys with inter-regional collaborations are needed to evaluate the home range and population status of this endangered species for their effective conservation in one of the busiest waterways of the world.

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Marine vessels alter the behaviour of bottlenose dolphins Tursiops truncatus in the Istanbul Strait, Turkey

Cited by 23 publications

References 42 publications

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

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

The effects of vessel noise on the communication network of humpback whales

Encounter rate, residency pattern and site fidelity of bottlenose dolphins (Tursiops truncatus) within the Istanbul Strait, Turkey

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