Marine apex predators, such as coastal dolphins, are key components of ecosystem function and dynamics; understanding their spatial use therefore is important for conservation planning. Here, we describe spatial use of the threatened Guiana dolphin, Sotalia guianensis, within a mosaic of protected areas at their southern range in the Paranaguá estuarine complex (PEC), Brazil. Based on environmental characteristics and S. guianensis population densities, individual photo-identification surveys were focused on two sectors of the northern mouth of the PEC between 2013 and 2015. We photo-identified 107 individuals and recorded 351 groups of Guiana dolphins; nearly 50% of which contained calves. Group sizes were small (mean ± SD: Sector 1 = 3.4 ± 2.7; Sector 2 = 3.6 ± 2.0) and ranged from 1 to 30 individuals. Clustering algorithms were applied to resighted, photo-identified Guiana dolphins to classify individuals as “residents” (sighted in 87% of surveys, n = 11) and “transients” (two clusters; 62%, n = 22; 95%, n = 72). All individuals predominantly were observed foraging (90% in Sector 1 and 76% in Sector 2), but spatial use by transient individuals differed from the residents in terms of environmental (slope, water depth, and rainfall) and behavioral factors (presence of calves and foraging behavior). Compared to transients, resident dolphins ranged over smaller areas, typically more suitable for feeding, calf caring, and more protected from predators and vessels. Because resident Guiana dolphins exhibit small home ranges, they are particularly vulnerable to local anthropogenic activities and habitat loss. These characteristics imply a strong need for regionalized management plans to reduce negative impacts and to maintain the ecological functionality of the species.

中文翻译：

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影响圭亚那海豚（Sotalia guianensis）空间利用个体差异的环境和行为因素

海洋顶级捕食者，如沿海海豚，是生态系统功能和动态的关键组成部分；因此，了解它们的空间用途对于保护规划很重要。在这里，我们描述了受威胁的圭亚那海豚 Sotalia guianensis 在巴西巴拉那瓜河口复合体 (PEC) 南部范围的保护区内的空间使用。根据环境特征和圭亚那海豚种群密度，2013年至2015年期间，对PEC北部口的两个区域进行了个体照片识别调查。我们对107名个体进行了照片识别，并记录了351组圭亚那海豚；其中近 50% 含有小牛。小组规模较小（平均值 ± SD：第 1 区 = 3.4 ± 2.7；第 2 区 = 3.6 ± 2.0），范围从 1 到 30 个人。聚类算法被应用于重新观察、照片识别的圭亚那海豚，将个体分类为“居民”（在 87% 的调查中发现，n = 11）和“瞬态”（两个集群；62%，n = 22；95%，n = 72)。主要观察到所有个体觅食（第 1 区为 90%，第 2 区为 76%），但在环境（坡度、水深和降雨量）和行为因素（小牛的存在）方面，短暂个体的空间使用与居民不同和觅食行为）。与瞬态海豚相比，常驻海豚分布在更小的区域，通常更适合喂养、照顾小牛，并且更能免受捕食者和船只的伤害。由于居民圭亚那海豚的栖息地范围很小，它们特别容易受到当地人为活动和栖息地丧失的影响。