Changes in whistle structure of resident bottlenose dolphins in relation to underwater noise and boat traffic

2016 ◽  
Vol 105 (1) ◽  
pp. 193-198 ◽  
Author(s):  
Nikolina Rako Gospić ◽  
Marta Picciulin
Keyword(s):  
Bottlenose Dolphins ◽  
Underwater Noise ◽  
Boat Traffic

scholarly journals Dolphin-Watching Boats Affect Whistle Frequency Modulation in Bottlenose Dolphins

2021 ◽  
Vol 8 ◽  
Author(s):  
Betzi Perez-Ortega ◽  
Rebecca Daw ◽  
Brennan Paradee ◽  
Emma Gimbrere ◽  
Laura J. May-Collado
Keyword(s):  
Bottlenose Dolphins ◽  
Emotional States ◽  
National Guidelines ◽  
Bocas Del Toro ◽  
System A ◽  
Potential Association ◽  
Boat Traffic ◽  
A Site ◽  
Signature Whistle ◽  
Dolphin Watching

Bottlenose dolphins’ whistles are key in social communication, conveying information about conspecifics and the environment. Therefore, their study can help to infer habitat use and identify areas of concern due to human activities. Here we studied the whistles of bottlenose dolphins (Tursiops truncatus) in two sites of the archipelago of Bocas del Toro, Panama, that contrast in boat traffic. Almirante Bay is a site dominated by taxi-boats and Dolphin Bay is a major location for boat-based dolphin watching. Recordings were made using bottom-mounted hydrophones and from the research boat using an over-the-side hydrophone and a broadband recording system. A total recording effort time of 1,726 h was analyzed. Our results show significant differences in boat detection between sites, and a higher number of whistles detected per minute in the site with tour-boat traffic. Furthermore, whistle modulation accounted for most of the differences between sites, boat presence, and whistle types. Dolphin whistle modulation is thought to be a potential indicator of emotional states including danger, alertness, and stress. In this study, dolphin signature whistle modulation increased significantly with boat presence in both sites but changes in modulation were greater in Dolphin Bay where tour-boats directly and sometimes aggressively interact with the animals. These results support a potential association between whistle modulation and stress (or alertness). These findings indicate that if tour-boat captains behave more like taxi-boat captains by e.g., reducing the distance of approach and contact time during dolphin interactions, dolphin communication, and emotional state would be less disrupted. These measures are implemented in the national guidelines for whale-watching and are known to tour-boat operators. The key to protecting these dolphins is in finding ways to effectively enforce these operator guidelines.

Monitoring important coastal sites for bottlenose dolphin in Cardigan Bay, UK

2009 ◽  
Vol 89 (5) ◽  
pp. 1033-1043 ◽  
Author(s):  
Chris Pierpoint ◽  
Liz Allan ◽  
Holly Arnold ◽  
Peter Evans ◽  
Sarah Perry ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Bottlenose Dolphins ◽  
Coastal Zone Management ◽  
Site Occupancy ◽  
Cost Effective ◽  
County Council ◽  
Monitoring Site ◽  
Positive Trend ◽  
Site Use ◽  
Boat Traffic

From 1994–2007 Ceredigion County Council and a network of shore-based, volunteer observers monitored levels of boat traffic and the occurrence of bottlenose dolphins Tursiops truncatus at seven sites on the coast of Cardigan Bay, Wales. We report high rates of site use and site occupancy by this species during the summer: at Mwnt for example, dolphins were recorded in >80% of 2 hours' observation periods; and at New Quay Harbour dolphins were present in >30% of all 15-minute intervals. At Mwnt and Aberporth there was a significant annual trend for increasing sighting rates; at Ynys Lochtyn a positive trend was only marginally non-significant; at New Quay Bird's Rock the trend was ambiguous but appeared stable over the seven most recent years. Although trends in site use may not reflect population trends in the wider region, these data were consistent with recent abundance estimates that indicate that the number of bottlenose dolphins using Cardigan Bay is stable or slightly increasing. Average group size at our study sites was small (<3 animals), which contrasts with observations of larger schools of the same population elsewhere in their range. The predominant behaviour in coastal Cardigan Bay is demersal foraging, often by solitary animals in shallow near-shore habitats. There was evidence that boat traffic suppressed site use by dolphins at New Quay Harbour, the busiest monitoring site: sighting rates fell when high numbers of boats were present and sighting rates were higher in 2007 than in previous years, when boat use was reduced due to poor weather during the main tourist season. This study demonstrates that networks of volunteer observers can provide a cost-effective, non-invasive means of gathering data on marine mammals for the purposes of coastal zone management.

Bottlenose dolphins around Aberdeen harbour, north-east Scotland: a short study of habitat utilization and the potential effects of boat traffic

2005 ◽  
Vol 85 (6) ◽  
pp. 1547-1554 ◽  
Author(s):  
M.I. Sini ◽  
S.J. Canning ◽  
K.A. Stockin ◽  
G.J. Pierce
Keyword(s):  
East Coast ◽  
Bottlenose Dolphins ◽  
High Tide ◽  
Habitat Utilization ◽  
Late Afternoon ◽  
North East ◽  
The North ◽  
Early Afternoon ◽  
Boat Traffic

The aim of this study was to investigate the factors that affect the patterns of occurrence and habitat utilization of bottlenose dolphins around Aberdeen harbour, on the north-east coast of Scotland (UK), and their responses to boat traffic. Land-based surveys were conducted over a period of nine weeks, between early May and late July, 2002. During this time 83 sightings of bottlenose dolphins were recorded. Dolphins occurred more frequently around midday and early afternoon, while their abundance was greater around high tide and late afternoon. Foraging was the most commonly observed activity.Dolphins were usually concentrated around the entrance of Aberdeen harbour. Their responses to boats varied considerably according to boat size, activity and speed, but there is evidence of habituation to boat traffic.

scholarly journals Distribución espacial, estructura social y amenazas de conservación de una pequeña comunidad de delfines nariz de botella, Tursiops trunca (Odontoceti: Delphinidae) en Ecuador

2019 ◽  
Vol 67 (4) ◽  
Author(s):  
Fernando Félix ◽  
Melanie Zavala ◽  
Ruby Centeno
Keyword(s):  
Group Size ◽  
Tursiops Truncatus ◽  
Marine Protected Area ◽  
Bottlenose Dolphins ◽  
Northwestern Part ◽  
Small Community ◽  
Population Unit ◽  
Fishing Boat ◽  
Boat Traffic ◽  
Santa Elena

Socio-ecological and conservation aspects of a small community of bottlenose dolphins Tursiops truncatus (Odontoceti: Delphinidae) in Santa Elena, Ecuador. A resident community of bottlenose dolphins (Tursiops truncatus) has been studied irregularly between 2005 and 2018 around the tip of the Santa Elena Peninsula, Ecuador (2°11'S, 81°0.7'W). Opportunistic sightings and systematic surveys from the beach and at sea from a boat were carried out along 40 km of coast, accounting for 917.2 km of tracking by car from land and 707.4 km of boat tracking by sea. Average group size was 5.31 dolphins/group (SD= 1.97, range 1-10), with no significant changes throughout the study period. From land, however, the group size was underestimated 32% on the average. This small dolphin community currently has only nine individuals, including six adults, one immature and two calves. The relative abundance ranged between 0.03 dolphins/km in the northwestern part and 0.32 dolphins/km in the south, where dolphins concentrate their activities, possibly because human activities are less intense. Dolphins were generally distributed in the first 200 m from the shore, reaching up to 1,200 in the northern shallower part and where port and tourist activities concentrate. The dolphins’ speed was significantly higher when they were followed from a boat at close range (5.87 km/h) than when they were monitored from the beach (2.9 km/h) (P < 0.01), which suggests that boat tracking had an effect on dolphin´s movements. Pairwise cluster analysis showed that animals from this community show high rates of association among each other (average 0.67, range 0.01-1.0), indicating this is highly cohesive population unit. Dolphins also showed high level of residence (average occurrence index = 0.62). During the study, two main threats were identified, a gillnet fishery in the southwestern part and an intense fishing boat traffic in the northwestern. This coastal bottlenose dolphin community is the smallest of this species ever reported in the Gulf of Guayaquil, probably is a remnant of a larger population that would be in process of extinction. Most of the study area is currently part of a coastal-marine protected area created in 2008, which offers an opportunity for the recovery and conservation of this dolphin community. Given the fragility of this population unit, we recommend to environment authorities addressing potential threats by eliminating gillnets, implementing an exclusion zone for fishing gear and fishing boat traffic of 1 km width from the shore and limit the speed of any type of vessel to 10 knots within the reserve.

Theoretical approach to estimating the induction of hearing impairment in bottlenose dolphins by radiated leisure boat noise

2011 ◽  
Vol 92 (8) ◽  
pp. 1887-1892 ◽  
Author(s):  
Jonathan A. David
Keyword(s):  
Hearing Impairment ◽  
Coastal Waters ◽  
Sound Pressure ◽  
Bottlenose Dolphins ◽  
Pressure Level ◽  
Threshold Shift ◽  
Temporary Threshold Shift ◽  
Underwater Noise ◽  
Noise Levels ◽  
Close Range

Coastal waters are being subjected to underwater noise generated by increasing numbers of leisure and tour boats. Such noise has the potential to impair the hearing of neighbouring bottlenose dolphins, particularly as the noise from several distributed boats could summate at the point of reception. This potential has been assessed by comparing small boat noise, recorded over a range of 8–532 m, with noise that is known to induce hearing impairment in the form of a temporary threshold shift (TTS) or permanent threshold shift (PTS). Extrapolation of broadband boat noise levels yielded a minimum source sound pressure level of 156 dB re 1μPa at 1 m. An equal-energy model for TTS-onset predicted that boat noise could induce a TTS after 1 hour's exposure at 1.3 m and after 8 hours' exposure at 2.3 m. These distances increased with additional adjacent boats. Leisure boats are unlikely to induce a PTS, even at close range.

scholarly journals Predicting the effects of human developments on individual dolphins to understand potential long-term population consequences

2015 ◽  
Vol 282 (1818) ◽  
pp. 20152109 ◽  
Author(s):  
Enrico Pirotta ◽  
John Harwood ◽  
Paul M. Thompson ◽  
Leslie New ◽  
Barbara Cheney ◽  
...  
Keyword(s):  
Sublethal Effects ◽  
Bottlenose Dolphins ◽  
Vital Rates ◽  
Motivational States ◽  
Multi Stage ◽  
Population Consequences ◽  
Calf Survival ◽  
Boat Traffic ◽  
Analytical Tools

Human activities that impact wildlife do not necessarily remove individuals from populations. They may also change individual behaviour in ways that have sublethal effects. This has driven interest in developing analytical tools that predict the population consequences of short-term behavioural responses. In this study, we incorporate empirical information on the ecology of a population of bottlenose dolphins into an individual-based model that predicts how individuals' behavioural dynamics arise from their underlying motivational states, as well as their interaction with boat traffic and dredging activities. We simulate the potential effects of proposed coastal developments on this population and predict that the operational phase may affect animals' motivational states. For such results to be relevant for management, the effects on individuals' vital rates also need to be quantified. We investigate whether the relationship between an individual's exposure and the survival of its calves can be directly estimated using a Bayesian multi-stage model for calf survival. The results suggest that any effect on calf survival is probably small and that a significant relationship could only be detected in large, closely studied populations. Our work can be used to guide management decisions, accelerate the consenting process for coastal and offshore developments and design targeted monitoring.

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