Whistle rates of wild bottlenose dolphins (Tursiops truncatus): Influences of group size and behavior.

2008 ◽  
Vol 122 (3) ◽  
pp. 305-311 ◽  
Author(s):  
Nicola J. Quick ◽  
Vincent M. Janik
Keyword(s):  
Group Size ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
And Behavior

Influence of artisanal fisheries on the behaviour and social structure of Tursiops truncatus in the South-western Gulf of Mexico

2019 ◽  
Vol 99 (8) ◽  
pp. 1841-1849
Author(s):  
Nataly Morales-Rincon ◽  
Eduardo Morteo ◽  
Christian Alejandro Delfín-Alfonso
Keyword(s):  
Gulf Of Mexico ◽  
Group Size ◽  
Age Structure ◽  
Human Activities ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Vantage Point ◽  
Competitive Interactions ◽  
Artisanal Fisheries ◽  
Behavioural Plasticity

AbstractBehavioural plasticity in animals is tested whenever competitive interactions for space and/or food resources occur between wildlife and human activities. This study uses the concepts of operational and non-operational interactions between bottlenose dolphins (Tursiops truncatus) and artisanal fisheries in Alvarado, to search for differences in behaviour, age structure and group size. We conducted 20 surveys between 2015 and 2016, and recorded 64 groups by means of scan sampling from either a research boat or a fixed vantage point. Average dolphin group size was small (${\bar{\rm x}}$ = 3.2, SD = 2.2 individuals) and fewer individuals were commonly present when interaction with fisheries occurred. Operational interactions were defined within the first 30 m and occurred mainly with lone individuals (54% recorded from the lighthouse and 82% during surveys); this benchmark also accounted for higher frequencies in locomotion and feeding (χ2 = 83.10; df = 7; P < 0.001). We found a higher rate of new behavioural events for dolphin groups furthest from human activities, as well as a decrease in behaviours that imply greater body exposure as dolphins approach the fishing spots. Age structure and dolphin group size were not different during and in the absence of interaction with fisheries, but most interactions involved male dolphins. Behavioural variations in the dolphins' repertoire are likely a strategy to reduce the risk of injuries or death when interacting with human activities; these dolphins seem to have habituated to or at least tolerate fishing activities within the study area, possibly constituting a sex-biased pressure.

scholarly journals The diving physiology of bottlenose dolphins (Tursiops truncatus). II. Biomechanics and changes in buoyancy at depth

1999 ◽  
Vol 202 (20) ◽  
pp. 2749-2761 ◽  
Author(s):  
R.C. Skrovan ◽  
T.M. Williams ◽  
P.S. Berry ◽  
P.W. Moore ◽  
R.W. Davis
Keyword(s):  
Tursiops Truncatus ◽  
Marine Mammals ◽  
Bottlenose Dolphins ◽  
Neutral Buoyancy ◽  
Swimming Mode ◽  
Locomotor Patterns ◽  
The Cost ◽  
Physical Changes ◽  
And Behavior ◽  
Limited Oxygen

During diving, marine mammals must balance the conservation of limited oxygen reserves with the metabolic costs of swimming exercise. As a result, energetically efficient modes of locomotion provide an advantage during periods of submergence and will presumably increase in importance as the animals perform progressively longer dives. To determine the effect of a limited oxygen supply on locomotor performance, we compared the kinematics and behavior of swimming and diving bottlenose dolphins. Adult bottlenose dolphins (Tursiops truncatus) were trained to swim horizontally near the water surface or submerged at 5 m and to dive to depths ranging from 12 to 112 m. Swimming kinematics (preferred swimming mode, stroke frequency and duration of glides) were monitored using submersible video cameras (Sony Hi-8) held by SCUBA divers or attached to a pack on the dorsal fin of the animal. Drag and buoyant forces were calculated from patterns of deceleration for horizontally swimming and vertically diving animals. The results showed that dolphins used a variety of swimming gaits that correlated with acceleration. The percentage of time spent gliding during the descent phase of dives increased with depth. Glide distances ranged from 7.1+/−1.9 m for 16 m dives to 43.6+/−7.0 m (means +/− s.e.m.) for 100 m dives. These gliding patterns were attributed to changes in buoyancy associated with lung compression at depth. By incorporating prolonged glide periods, the bottlenose dolphin realized a theoretical 10–21 % energetic savings in the cost of a 100 m dive in comparison with dives based on neutral buoyancy models. Thus, modifying locomotor patterns to account for physical changes with depth appears to be one mechanism that enables diving mammals with limited oxygen stores to extend the duration of a dive.

scholarly journals Investigation of Environmentally Dependent Movement of Bottlenose Dolphins (Tursiops truncatus)

2021 ◽  
Vol 2 (3) ◽  
pp. 335-348
Author(s):  
Zining Zhang ◽  
Ding Zhang ◽  
Joaquin Gabaldon ◽  
Kari Goodbar ◽  
Nicole West ◽  
...  
Keyword(s):  
Animal Behavior ◽  
Network Architecture ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Video Frame ◽  
Neural Network Architecture ◽  
Environmental Stimuli ◽  
And Behavior ◽  
Lagoon Environment ◽  
Persistent Monitoring

How environmental features (e.g., people, enrichment, or other animals) affect movement is an important element for the study of animal behavior, biomechanics, and welfare. Here we present a stationary overhead camera-based persistent monitoring framework for the investigation of bottlenose dolphin (Tursiops truncatus) response to environmental stimuli. Mask R-CNN, a convolutional neural network architecture, was trained to automatically detect 3 object types in the environment: dolphins, people, and enrichment floats that were introduced to stimulate and engage the animals. Detected objects within each video frame were linked together to create track segments across frames. The animals’ tracks were used to parameterize their response to the presence of environmental stimuli. We collected and analyzed data from 24 sessions from bottlenose dolphins in a managed lagoon environment. The seasons had an average duration of 1 h and around half of them had enrichment (42%) while the rest (58%) did not. People were visible in the environment for 18.8% of the total time (∼4.5 h), more often when enrichment was present (∼3 h) than without (∼1.5 h). When neither enrichment nor people were present, the animals swam at an average speed of 1.2 m/s. When enrichment was added to the lagoon, average swimming speed decreased to 1.0 m/s and the animals spent more time moving at slow speeds around the enrichment. Animals’ engagement with the enrichment also decreased over time. These results indicate that the presence of enrichment and people in, or around, the environment attracts the animals, influencing habitat use and movement patterns as a result. This work demonstrates the ability of the proposed framework for the quantification and persistent monitoring of bottlenose dolphins’ movement, and will enable new studies to investigate individual and group animal locomotion and behavior.

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.

scholarly journals Interactions between Mediterranean bottlenose dolphins (Tursiops truncatus) and gillnets off Sardinia, Italy

2006 ◽  
Vol 63 (5) ◽  
pp. 946-951 ◽  
Author(s):  
Bruno Díaz López
Keyword(s):  
Group Size ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Size Analysis ◽  
Encounter Rate ◽  
New Approach ◽  
Annual Loss ◽  
Direct Observations ◽  
Annual Estimate ◽  
Northeastern Coast

Abstract A first attempt at analysing interactions between bottlenose dolphins and gillnets along the northeastern coast of Sardinia (Italy) was conducted between October 1999 and December 2004. A new approach was used: combining interviews with fishers with boat-based direct observations and behavioural and group size analysis. Fishers on monitored boats noted 2556 days on which gillnet damage was caused by bottlenose dolphins, 68.7% of the total fishing days, with no difference between seasons. An annual estimate of the number of bottlenose dolphins caught in the gillnets was 1.47 (0.98 immatures and 0.49 adults). In all, 317 days were spent making observations at sea, of which 330.6 h were spent directly observing the dolphins. There were no changes in the distribution of daily encounter rate among seasons, group size, or number of immatures, in the presence or the absence of gillnets. However, bottlenose dolphins spent more time both in the study area and feeding when gillnets were present. The extent of the estimated bycatch is worrisome in terms of the ability of bottlenose dolphins off Sardinia to sustain such an annual loss.

Seasonal Abundance and Site Fidelity of Bottlenose Dolphins (Tursiops truncatus) in Mississippi Sound

2004 ◽  
Vol 30 (2) ◽  
pp. 299-310 ◽  
Author(s):  
Carrie W. Hubard ◽  
Kathy Maze-Foley ◽  
Keith D. Mullin ◽  
William W. Schroeder
Keyword(s):  
Tursiops Truncatus ◽  
Site Fidelity ◽  
Bottlenose Dolphins ◽  
Seasonal Abundance ◽  
Mississippi Sound

Whale Poaching Detection Based on Microscopic Characteristics of Bottlenose Dolphins’ (Tursiops truncatus) Bone Fragments

2018 ◽  
Vol 43 (5) ◽  
pp. 519-528
Author(s):  
Manuela Zadravec ◽  
Zvonimir Kozarić ◽  
Snježana Kužir ◽  
Mario Mitak ◽  
Tomislav Gomerčić ◽  
...  
Keyword(s):  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Bone Fragments
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