Collaborative Research: Causes of Variation in Parid Call Complexity

人类语言是已知的最复杂的交流系统。然而，许多非人类的动物物种也有相当复杂的交流系统，包括非人类灵长类动物、鲸鱼和海豚，甚至许多鸟类。然而，对于人类语言和非人类交流系统来说，导致这种复杂性的关键因素在很大程度上仍然未知。发现这些因素对于理解这些复杂行为的起源和进化至关重要，包括我们自己祖先的语言起源。该研究将采用观察和实验的方法来检验解释声音交流复杂性的三个关键因素：社会复杂性和群体规模、捕食风险和栖息地对声音传播的限制。研究人员将在两种常见的北美鸟类中研究这些因素，这两种鸟类拥有复杂的发声行为系统和复杂的社会结构：卡罗莱纳山雀和簇状山雀。研究人员将把他们的研究成果纳入教学，并指导多名学生研究人员使用当前的研究方法，包括大数据管理策略，并通过与伊利诺伊大学超级计算设施相关的极端科学与工程发现环境项目与超级计算人员合作。卢卡斯和弗里伯格将继续为《美国科学家》（American Scientist）等普通读者期刊撰写有关这项工作的文章。2012年，他们在《美国科学家》上共同撰写了一篇文章，该文章在美国和海外被成千上万的读者阅读。是什么因素推动了复杂信号的演变？社会复杂性假说认为，形成复杂社会群体的物种或种群比形成简单群体的物种或种群需要更复杂的信号系统。尽管有越来越多的证据支持社会复杂性假说，但一个关键的限制是，它很少与其他假设进行对比。该研究使用了两种鸟类（卡罗莱纳山雀，Poecile carolinensis，和簇状山雀，Baeolophus bicolor）的鸣叫声来测试社会复杂性假说和两种主要的替代假说来解释交流复杂性：(1)社会复杂性：在更复杂的鸟群中，个体发出的叫声比在更简单的鸟群中发出的叫声更复杂。(2)生境限制：生境越开放的个体发出的叫声比生境越封闭的个体发出的叫声更复杂。(3)捕食压力：与捕食者较少的个体相比，捕食者密度较大或多样性较大的个体发出的叫声更复杂。这些假设将通过田纳西大学和佛罗里达大学的圈养羊群实验、未被操纵的野生羊群收集的数据、野外回放实验以及在田纳西大学和普渡大学计划的部分森林砍伐前后对羊群的观察，以前所未有的分辨率进行测试。这项工作将增加对复杂交际行为的功能和机制的理解，并提供关于个人层面的复杂行为如何从个人生活的社会和物理环境的本质中产生的基本信息。在动物群落中，非亲缘物种通常被用作研究社会信息使用及其适应性后果的模型系统。这项工作为理解鸟类叫声复杂性的本质奠定了坚实的基础，反过来，在快速变化的世界中，许多物种在适应相关决策中使用的精细调整信息的产生。研究人员打算将这些数据存放在田纳西大学的机构存储库Trace （http://trace.tennessee.edu/）中，田纳西大学图书馆的工作人员将在那里为长期保存和管理提供评估。Trace解决了存储研究的访问、安全、保存和版权问题，并确保全球研究人员可以找到数据，并通过数字对象标识符（doi）的分配鼓励适当的引用和重用。

Human language is the most complex communication system known. However, many non-human animal species also have quite complex communication systems, including non-human primates, whales and dolphins, and even many bird species. The key factors driving such complexity, though, remain largely unknown for both human language and for non-human communication systems. Discovering these factors is crucial to understanding the origin and evolution of such complex behavior, including the origin of language in our own ancestors. The proposed research will use observational and experimental methods to test three key factors proposed to explain vocal communication complexity: social complexity and group size, predation risk, and habitat-induced constraints on sound transmission. The investigators will examine these factors in two common North American bird species that possess complex systems of vocal behavior as well as complex social structures: Carolina chickadees and tufted titmice. The researchers will include their results in their teaching and mentor multiple student researchers in current research methods including Big Data management strategies, and collaborting with supercomputing staff through the Extreme Science and Engineering Discovery Environment program associated with the University of Illinois supercomputing facility. Lucas and Freeberg will continue to write about this work for general-audience journals like American Scientist, where they co-authored a 2012 article that has been read by thousands of readers in the U.S. and abroad.What factors drive the evolution of complex signals? The Social Complexity Hypothesis posits that species or populations forming complex social groups require more complex signaling systems than species or populations that form simpler groups. Although there is increasing evidence to support the Social Complexity Hypothesis, a key limitation is that it is rarely tested against alternative hypotheses. The proposed work tests the Social Complexity Hypothesis against two major alternative hypotheses to explain communicative complexity, using chick-a-dee calls of two avian species of the family Paridae (Carolina chickadees, Poecile carolinensis, and tufted titmice, Baeolophus bicolor): (1) Social Complexity: Individuals in more complex flocks produce calls with greater complexity than individuals in simpler flocks. (2) Habitat Constraints: Individuals in habitats that are more open produce calls with greater complexity than individuals in more closed habitats. (3) Predation Pressure: Individuals in habitats with a greater density or diversity of predators produce calls with greater complexity than individuals facing fewer predators. The hypotheses will be tested with unprecedented resolution through captive flock experiments at the University of Tennessee and University of Florida, data collected on un-manipulated wild flocks, field playback experiments, and observations of flocks before and after scheduled partial forest cuts at the University of Tennessee and Purdue University. The work will increase understanding of the function and mechanisms of complex communicative behavior and provide fundamental information about how complex behavior at the level of the individual emerges from the nature of the social and physical environmental setting in which the individual lives. Parid species are now commonly utilized as a model system for the study of social information use and its fitness consequences in animal communities. This work lays a solid foundation for understanding the nature of parid call complexity and, in turn, the generation of finely tuned information used by many species in fitness-related decision-making in a rapidly changing world. The investigators intend to deposit the data in the University of Tennessee institutional repository, Trace (http://trace.tennessee.edu/), where University of Tennessee Libraries staff will provide appraisal for long-term preservation and stewardship. Trace addresses access, security, preservation, and copyright of deposited research, and ensures that global researchers can find the data, with the assignment of Digital Object Identifiers (DOIs) encouraging proper citation and re-use.