Uhl Florian, Ringler Max, Miller Rachael, Deventer Sarah A, Bugnyar Thomas, Schwab Christine
Department of Cognitive Biology, University of Vienna, Vienna, Austria.
Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, CA, USA.
Behav Ecol. 2019 Jan-Feb;30(1):57-67. doi: 10.1093/beheco/ary157. Epub 2018 Dec 8.
Social complexity arises from the formation of social relationships like social bonds and dominance hierarchies. In turn, these aspects may be affected by the degree of fission-fusion dynamics, i.e., changes in group size and composition over time. Whilst fission-fusion dynamics has been studied in mammals, birds have received comparably little attention, despite some species having equally complex social lives. Here, we investigated the influence of environmental factors on aspects of fission-fusion dynamics in a free-ranging population of carrion and hooded crows (.) in the urban zoo of Vienna, Austria over a 1-year period. We investigated 1) the size and 2) spatio-temporal structure of the local flock, and 3) environmental influences on local flock and subgroup size. The local flock size varied considerably over the year, with fewest birds being present during the breeding season. The spatio-temporal structure of the local flock showed 4 distinct presence categories, of which the proportions changed significantly throughout the year. Environmental effects on both local flock and subgroup size were time of day, season, temperature, and weather, with additional pronounced effects of the structure of the surroundings and age class on subgroup size. Our findings show environmental influences on party size at the local flock and subgroup level, as well as indications of structured party composition in respect to the 4 presence categories. These results suggest that environmental factors have significant effects on fission-fusion dynamics in free-ranging crows, thereby influencing social complexity.
社会复杂性源于社会关系的形成，如社会纽带和优势等级制度。反过来，这些方面可能会受到裂变-融合动态程度的影响，即群体规模和组成随时间的变化。虽然哺乳动物中的裂变-融合动态已得到研究，但鸟类受到的关注相对较少，尽管有些鸟类也有着同样复杂的社会生活。在此，我们在奥地利维也纳城市动物园对自由放养的食腐鸦和秃鼻乌鸦种群进行了为期一年的研究，调查环境因素对裂变-融合动态各方面的影响。我们研究了：1）当地鸟群的规模；2）当地鸟群的时空结构；3）环境对当地鸟群和亚群规模的影响。当地鸟群规模在一年中变化很大，繁殖季节鸟的数量最少。当地鸟群的时空结构呈现出4种不同的出现类别，其比例在一年中发生了显著变化。对当地鸟群和亚群规模产生环境影响的因素包括一天中的时间、季节、温度和天气，此外，周围环境结构和年龄类别对亚群规模有更显著的影响。我们的研究结果表明环境对当地鸟群和亚群层面的群体规模有影响，以及在4种出现类别方面有结构化群体组成的迹象。这些结果表明，环境因素对自由放养乌鸦的裂变-融合动态有显著影响，从而影响社会复杂性。
