Department of Evolution, Ecology, and Behavior, School of Integrative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Biology, East Carolina University, Greenville, NC 27858, USA; International Research Center for Neurointelligence, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Department of Biology, East Carolina University, Greenville, NC 27858, USA.
Curr Biol. 2019 Dec 2;29(23):4045-4051.e3. doi: 10.1016/j.cub.2019.09.046. Epub 2019 Nov 14.
How does a naive, young animal decide from which adults to learn behavior? Obligate brood parasitic birds, including brown-headed cowbirds (Molothrus ater), face a particular challenge in learning species-specific behaviors; they lay their eggs in the nest of another species, and juveniles are raised without exposure to adult conspecifics. Nevertheless, male cowbirds need to learn a conspecific song to attract appropriate mates, and female cowbirds need to learn to identify conspecific males for mating. Traditionally, it was thought that parasitic bird species rely purely on instinctual species recognition [1-4], but an alternative is that a species-specific trait serves as a "password" [5], a non-learned cue for naive animals that guides decisions regarding from whom to learn. Here, we tested the hypothesis that the adult "chatter call" enhances the learning of specific songs in juvenile cowbirds. We exposed acoustically naive juvenile male and female cowbirds to songs paired with chatter calls and found that the chatter call enhanced song production learning in males and induced a neurogenomic profile of song familiarity in females, even for heterospecific songs. Thus, a combination of experience-independent and -dependent mechanisms converges to explain how young cowbirds emerge from another species' nest yet learn behaviors from conspecifics. Identifying whether such password-based mechanisms relate to perceptual and behavioral learning in non-parasitic taxa will contribute to our general understanding of the development of social recognition systems.
年幼而天真的动物是如何决定向哪些成鸟学习行为的呢？包括褐头牛鹂（Molothrus ater）在内的专性巢寄生鸟类在学习特定物种行为方面面临着特殊的挑战；它们将卵产在其他物种的巢中，幼鸟在成长过程中不会接触到成年同种个体。然而，雄性牛鹂需要学习同种鸣叫声来吸引合适的配偶，而雌性牛鹂需要学会识别同种雄性来进行交配。传统上，人们认为寄生鸟类纯粹依赖于本能的物种识别[1-4]，但另一种观点认为，一种特定于物种的特征充当了“密码”[5]，即一种无学习的线索，为天真的动物提供了指导，决定向谁学习。在这里，我们测试了一个假设，即成年的“啁啾叫声”增强了幼年牛鹂对特定歌曲的学习能力。我们让听觉上不成熟的雄性和雌性幼年牛鹂接触与啁啾叫声配对的歌曲，发现啁啾叫声增强了雄性的歌曲产生学习能力，并诱导了雌性对歌曲熟悉的神经基因组特征，即使是异源歌曲也是如此。因此，一系列经验独立和依赖的机制共同解释了幼牛鹂如何从其他物种的巢中孵化出来，但却能从同种个体那里学习行为。确定这种基于密码的机制是否与非寄生类群的感知和行为学习有关，将有助于我们全面了解社会识别系统的发展。
