Blasi Monica F, Boitani Luigi
Filicudi WildLife Conservation, Località Stimpagnato Filicudi, 98055, Lipari (ME), Italy.
Department of Biology and Biotechnologies, University 'La Sapienza', Viale dell' Università 32, 00185, Rome, Italy.
PLoS One. 2014 Dec 10;9(12):e114849. doi: 10.1371/journal.pone.0114849. eCollection 2014.
We investigated social structure and association patterns for a small population of Mediterranean bottlenose dolphins, Tursiops truncatus, inhabiting the Aeolian Archipelago (southern Italy). Specifically we evaluate the role of sex and age composition, residency patterns and interaction with trammel nets on this social organization. Association data for 23 regularly sighted individuals were obtained from summer photoidentification surveys collected from 2005-2012. Using a combined cluster and social network analysis approach, we found associations between dolphins were hierarchically structured, where two mixed-sex social units were subdivided into smaller temporarily dynamic groups. We found non-random and long-term preferred associations in the population; however, the degree of social cohesion, residence pattern and interaction with trammel nets differed considerably between the two social units. Six of eight females occurred in the more resident social unit-1; in addition, social unit-1 individuals had significantly stronger associations, higher preferred associates, lived in larger groups and occurred less frequently with trammel nets. Nine of eleven males were clustered in social unit-2 and five of these males, interacting with trammel nets, formed small groups and preferred associations. We propose that female and male groups associate in the study area during the breeding season and that some males choose to interact with reproductive females forming a distinct but interrelated social unit. Other males may be associating in a larger fission-fusion network, which consists of dolphins that appear to temporarily join the network from the coastal population. We cannot exclude that some males specialized in trammel net foraging, suggesting that this foraging technique may favor a solitary lifestyle. Large group sizes and high degree of social cohesion for females could be an indication of greater protection and more efficiency in detecting, deterring or repelling anthropogenic pressures. Most likely dolphins' social organization depends on a combination of socio-ecological, demographic and anthropogenic factors.
我们调查了居住在伊奥利亚群岛（意大利南部）的一小群地中海宽吻海豚（Tursiops truncatus）的社会结构和关联模式。具体而言，我们评估了性别和年龄组成、居留模式以及与刺网的相互作用在这种社会组织中的作用。从2005年至2012年夏季的照片识别调查中获得了23只经常被目击个体的关联数据。使用聚类分析和社会网络分析相结合的方法，我们发现海豚之间的关联具有层次结构，其中两个混合性别的社会单位被细分为较小的临时动态群体。我们发现种群中存在非随机且长期的偏好关联；然而，两个社会单位之间的社会凝聚力程度、居留模式以及与刺网的相互作用存在很大差异。八只雌性中有六只出现在居留性更强的社会单位1中；此外，社会单位1的个体之间关联显著更强，有更高比例的偏好同伴，生活在更大的群体中，并且与刺网相遇的频率更低。十一只雄性中有九只聚集在社会单位2中，其中五只雄性与刺网相互作用，形成了小群体并存在偏好关联。我们提出，在繁殖季节，雌性和雄性群体在研究区域内聚集，并且一些雄性选择与繁殖期雌性互动，形成一个独特但相互关联的社会单位。其他雄性可能在一个更大的裂变 - 融合网络中聚集，该网络由似乎从沿海种群临时加入网络的海豚组成。我们不能排除一些雄性专门进行刺网觅食的可能性，这表明这种觅食技术可能有利于独居生活方式。雌性的大群体规模和高度的社会凝聚力可能表明在检测、威慑或抵御人为压力方面有更好的保护和更高的效率。很可能海豚的社会组织取决于社会生态、人口统计学和人为因素的综合作用。
