ABSTRACT: Phenotypic variations occur in several cetacean species, including common bottlenose dolphins Tursiops truncatus, which can also be distinguished as coastal and offshore ecotypes. In the western South Atlantic, these ecotypes have been described based on skeletal morphology and genetics. However, there is still no clear description to recognize them in the field. Here we searched for external diagnostic patterns that may facilitate their visual distinction and investigated their habitat use. We examined dorsal fin shapes and coloration of photo-identified dolphins distributed in a wide geographic range off the coast of southern and southeastern Brazil. A strong differentiation in the dorsal fin shape was observed, with a more falcate shape for offshore dolphins. We also found that offshore individuals have a darker color pattern, while coastal dolphins show 2 wider striped bands at the throat region and a longer rostrum, revealing that the ecotypes can be well distinguished in the field. We also detected differential habitat use. The coastal ecotype inhabits shallow waters (up to 18 m deep) close to the shore (up to 3 km). The offshore ecotype has a wider distribution and more flexible habitat use. It was usually found in coastal and deeper waters (maximum depth of 758 m and >200 km from the coast). Although we observed a small area of overlap in the distribution of the 2 ecotypes, both forms were not seen together. Therefore, our results reinforce the presence of a parapatric distribution and distinct morphology between the ecotypes, supporting their prior description as different subspecies.

中文翻译：

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南大西洋西部的宽吻海豚生态型：栖息地，着色图案和背鳍形状的难题

摘要：在几种鲸类物种中发生表型变异，包括常见的宽吻海豚Tursiops truncatus，也可以区分为沿海和近海生态型。在南大西洋西部，已经根据骨骼形态和遗传学描述了这些生态型。但是，仍然没有明确的描述来识别它们。在这里，我们搜索了可能有助于其视觉区别的外部诊断模式，并调查了它们的栖息地使用情况。我们研究了巴西南部和东南部沿海地区广泛分布的光识别海豚的背鳍形状和颜色。观察到背鳍形状有很强的区分性，近海海豚的形状则更为坚决。我们还发现，近海个体的颜色较暗，而沿海海豚的喉咙区域则有2条较宽的条纹，而讲台则较长，揭示了在该领域可以很好地区分生态型。我们还发现了不同的栖息地用途。沿海生态型栖息在靠近海岸（长达3公里）的浅水区（深达18 m）。离岸生态型分布更广，栖息地使用更灵活。通常在沿海和更深的水域发现（最大深度为758 m，距海岸> 200 km）。尽管我们在两种生态型的分布中观察到了很小的重叠区域，但是两种形式并没有一起出现。因此，我们的结果加强了生态型之间的父系分布和独特的形态，支持了它们先前作为不同亚种的描述。离岸生态型分布更广，栖息地使用更灵活。通常在沿海和更深的水域发现（最大深度为758 m，距海岸> 200 km）。尽管我们在两种生态型的分布中观察到了很小的重叠区域，但是两种形式并没有一起出现。因此，我们的结果加强了生态型之间的父系分布和独特的形态，支持了它们先前作为不同亚种的描述。离岸生态型分布更广，栖息地使用更灵活。通常在沿海和更深的水域发现（最大深度为758 m，距海岸> 200 km）。尽管我们在两种生态型的分布中观察到了很小的重叠区域，但是两种形式并没有一起出现。因此，我们的结果加强了生态型之间的父系分布和独特的形态，支持了它们先前作为不同亚种的描述。