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This article discusses a study that compares the whistles emitted by common bottlenose dolphins in three different regions: Revillagigedo Archipelago in Mexico, Saint Peter and Saint Paul Archipelago in Brazil, and the western Coast of Aragua in Venezuela. The study aims to understand the geographic variation in dolphin whistles in these regions. The study collected acoustic recordings from each location and analyzed the data to provide an overview of whistle variation among the studied areas. The results show that there are differences in whistle characteristics between the locations, suggesting that environmental adaptations, social factors, and genetic divergence may influence dolphin communication. Further research is needed to explore these factors in more detail. [Extracted from the article]

This study reports historic capture-mark-recapture survival and abundance estimates of common bottlenose dolphins (Tursiops truncatus) based on photo-identification surveys of coastal Venezuela (along the Aragua coast between Turiamo Bay and Puerto Colombia). We used the most recent data available: dolphins identified by unique dorsal fin marks during wet and dry season surveys conducted from 2004 to 2008. Dolphin encounter histories were analyzed in the Closed Capture Robust Design framework, with the top model including random movement, constant survival, and capture-recapture probabilities that varied by secondary periods. Survival of marked adults was estimated at 0.99 (95% CI = 0.97 to 1.00). Population estimates for all adults (marked and unmarked) averaged 31 animals (SD = 13.8), and for all dolphins (all adults and calves), 41 animals (SD = 17.2). Coastal bottlenose dolphins face numerous threats, including ship strikes, oil spills, conflict with recreational and industrial fisheries, other negative human interactions, biotoxins, chemicals, noise, freshwater discharge, and coastal development. Further, small populations are, in general, at increased risk due to reduced resiliency and recovery potential when exposed to such threats and to expected environmental and demographic stochasticity. These historic estimates of abundance and survival are critical for establishing a reference state and indicate a need for ongoing monitoring of the small dolphin population while the Aragua coast is still, as of yet, relatively little impacted by humans. Should coastal development increase (as is the global trend) and/or environmental catastrophes (e.g., harmful algal blooms, hurricanes, and oil spills) occur, these historic estimates will be essential for assessing impacts and guiding management and conservation interventions. Our results show year-round dolphin presence and highlight the Venezuelan coastal-oceanic landscape as an area of both future research and conservation importance. [ABSTRACT FROM AUTHOR]

The common dolphin (Delphinus sp.) is one of the most common cetaceans in Venezuela. This study aims to describe habitat use in the Mochima National Park, a protected area under high anthropogenic pressure. Opportunistic surveys were conducted following a pre‐defined route from September 2009 to August 2010. Data such as the geographical position, group size, composition, behaviour were recorded at 5min intervals. A focal group‐follow methodology was used. A grid of 500 × 500m was constructed and each cell was characterised by environmental features and a Coefficient of Area Use (CAU) was calculated. A logistic regression model was applied to identify factors that explain use pattern. Seventy opportunistic surveys were conducted during which 86 groups of dolphins were observed. Dolphins occupied an area of 36km², but Tigrillo inlet and to the northeast of the Caracas Islands were the areas most used. The common dolphins exhibited differential use, using shallow inshore waters most intensively and with probability of occurrence decreasing with increasing water depth and distance to the coast. They spent most of their time in feeding (40%) and socialising (24%) activities. Feeding and travelling behaviours were observed throughout the area studied, whereas socialising and resting activities were mainly concentrated in Tigrillo inlet, the Manare peninsula and the Caracas islands. Behaviour was mostly determined by season, depth, distance to the coast, group size and group composition. Throughout the year, the Park provided areas for refuge, feeding, and resting. It is therefore imperative to promote management and conservation policies that prevent any negative impacts from the increasing tourism and fishing activities we observed. [ABSTRACT FROM AUTHOR]