Impact of Vessel Transit on Vocalizations of the Taiwanese Humpback Dolphin

Hu, Wei-Chun; Siddagangaiah, Shashidhar; Chen, Chi‐Fang; Pieretti, Nadia

doi:10.3390/d14060426

Cited by 4 publications

(6 citation statements)

References 53 publications

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“…Our results show that different to previous works 9 – 11 , 13 , 14 that observed differences in the whistle rate when vessels are present, we did not observe such a linear relation in our dataset, and that there is overlap in distributions for the ’with’ and ’without’ vessel cases for each of the whistle features. While one possible explanation is that our results are specific for the four explored dolphins, the differences could also be explained by the high number of whistles and vessels explored, which may capture more complexities within the dataset.…”

Section: Discussioncontrasting

confidence: 99%

“…Here, we review the main methodologies. One recent work analysed the differences in the dolphins’ whistles emission rate and signal duration in the presence of vessel transit routes 9 . Roughly 1800 whistles were compared before, during, and after transit occurrences, and average differences were observed during and immediately after the passing of nearby vessels.…”

Section: Introductionmentioning

confidence: 99%

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Observational study on the non-linear response of dolphins to the presence of vessels

Diamant,

Testolin,

Shachar

et al. 2024

Sci Rep

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With the large increase in human marine activity, our seas have become populated with vessels that can be overheard from distances of even 20 km. Prior investigations showed that such a dense presence of vessels impacts the behaviour of marine animals, and in particular dolphins. While previous explorations were based on a linear observation for changes in the features of dolphin whistles, in this work we examine non-linear responses of bottlenose dolphins (Tursiops Truncatus) to the presence of vessels. We explored the response of dolphins to vessels by continuously recording acoustic data using two long-term acoustic recorders deployed near a shipping lane and a dolphin habitat in Eilat, Israel. Using deep learning methods we detected a large number of 50,000 whistles, which were clustered to associate whistle traces and to characterize their features to discriminate vocalizations of dolphins: both structure and quantities. Using a non-linear classifier, the whistles were categorized into two classes representing the presence or absence of a nearby vessel. Although our database does not show linear observable change in the features of the whistles, we obtained true positive and true negative rates exceeding 90% accuracy on separate, left-out test sets. We argue that this success in classification serves as a statistical proof for a non-linear response of dolphins to the presence of vessels.

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Section: Discussioncontrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Observational study on the non-linear response of dolphins to the presence of vessels

Diamant,

Testolin,

Shachar

et al. 2024

Sci Rep

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“…The busy vessel traffic in the Lingding waterway may further result in potential impacts on marine mammals including hearing masking and physiological damage to the auditory system (temporary threshold shift: TTS; permanent threshold shift: PTS), thereby shortening the communication distance of marine mammals (Merchant et al, 2014;Liu et al, 2017;Marley et al, 2017). When ships were presented, dolphins reduced vocalization behavior and emitted shorter calls in shorter frequency patterns, including whistles and echolocation signals (Hu et al, 2022). Hectic vessel traffic in the waters west of Hong Kong also interfered with the behavior and hearing of humpback dolphins (Sims et al, 2012).…”

Section: Underwater Noisementioning

confidence: 99%

Biosonar activity of the Indo-Pacific humpback dolphin (Sousa chinensis) near the tunnel section of the world’s longest cross-sea bridge—the Hong Kong-Zhuhai-Macao Bridge—is negatively correlated with underwater noise

Duan

et al. 2023

Front. Mar. Sci.

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Underwater noise pollution from the world’s longest cross-sea bridge—the Hong Kong-Zhuhai-Macao Bridge (HZMB)—which stretches across the Chinese White Dolphin National Nature Reserve (of the People’s Republic of China, PRC) in the Pearl River Estuary may affect the distribution of local humpback dolphins. In this study, static passive acoustic monitoring was applied to monitor biosonar activity of humpback dolphins and underwater noise adjacent to the tunnel section of the HZMB for more than one year. During the monitoring period, dolphin biosonar signals were detected on 88.5% of days. A significant temporal pattern occurred in dolphin biosonar activity and in anthropogenic noise. Biosonar activity was significantly higher at night than during the day, whereas underwater noise occurred more in the day than at night. Significantly more echolocation signals were detected in winter-spring than in summer-autumn, and highest acoustic activity occurred significantly more during high tide than at other tidal periods. In addition, the negative correlation between elevated underwater noise and dolphin sonar activity in winter suggests that dolphins may avoid noisy waters for short periods, perhaps due to auditory stress, but fish prey movement cannot be ruled out. These findings facilitate understanding activity patterns of humpback dolphins in the Pearl River Estuary and may contribute to conservation efforts.

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“…Because of this dolphin population's high site fidelity, the bay has become a hotspot for dolphin-watching activities occurring throughout the year, with boats arriving every day primarily between 9 a.m. to 12 p.m. (noon), but also in the afternoons depending on the season (Perez-Ortega et al, 2021). The boats used for this purpose are small (typically 10 m in length) and are fitted with one or two engines that can range between 50 and 110 hp (Hu et al, 2022).…”

Section: Study Sitementioning

confidence: 99%

“…Both baleen and toothed whales respond acoustically to boat noise exposure by adjusting signal emission rate (Guerra et al, 2014). Bottlenose dolphins (Luis et al, 2014), humpback dolphins (Hu et al, 2022), and right whales (Parks et al, 2007a) are reported to decrease mean call rates in the presence of vessels. Changes in signal amplitude and frequency are also reported in various cetacean species.…”

Section: Introductionmentioning

confidence: 99%

Dolphin communication during widespread systematic noise reduction-a natural experiment amid COVID-19 lockdowns

Gagne

Perez-Ortega

Hendry

et al. 2022

Front. Remote Sens.

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Underwater noise from human activities is recognized as a world-wide problem, with important repercussions on the acoustic communication of aquatic mammals. During the COVID-19 pandemic, the government of Panama went into a nationwide lockdown to limit the spread of the virus. This lockdown resulted in the closing of tourism infrastructure and limited mobility in both land and coastal areas. We used this “natural experiment” as an opportunity to study the impact of tour-boat activities on dolphin communication by using passive acoustic monitoring data collected before and during the lockdown at Dolphin Bay, Bocas del Toro, Panama. During the lockdown, tour-boat activity was absent, but boats transporting people and supplies were allowed to circulate. The shift in type of boat activity within the lockdown resulted in lower ambient noise levels and more frequent detections of dolphin sounds. We also detected a more diverse whistle repertoire during the lockdown than in the pre-lockdown period, even when accounting for variation in sample coverage. A Random Forest Analysis classified whistles between the two periods with high accuracy (92.4% accuracy, κ = 0.85) based primarily on whistle modulation and duration. During the lockdown, whistles were longer in duration and less modulated than pre-lockdown. Our study shows that a shift in boat traffic activity can generate significant changes in dolphin habitat, and in their communicative signals, an important consideration given ongoing unregulated ecotourism in the region.

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Impact of Vessel Transit on Vocalizations of the Taiwanese Humpback Dolphin

Cited by 4 publications

References 53 publications

Observational study on the non-linear response of dolphins to the presence of vessels

Observational study on the non-linear response of dolphins to the presence of vessels

Biosonar activity of the Indo-Pacific humpback dolphin (Sousa chinensis) near the tunnel section of the world’s longest cross-sea bridge—the Hong Kong-Zhuhai-Macao Bridge—is negatively correlated with underwater noise

Dolphin communication during widespread systematic noise reduction-a natural experiment amid COVID-19 lockdowns

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