de la Colina M A, Pompilio L, Hauber M E, Reboreda J C, Mahler B
Departamento de Ecología, Genética y Evolución and IEGEBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Department of Animal Biology, School of Integrative Biology, University of Illinois, Urbana-Champaign, IL, 61801, USA.
Anim Cogn. 2018 Mar;21(2):301-305. doi: 10.1007/s10071-018-1161-7. Epub 2018 Jan 25.
Obligate avian brood parasites lay their eggs in nests of other host species, which assume all the costs of parental care for the foreign eggs and chicks. The most common defensive response to parasitism is the rejection of foreign eggs by hosts. Different cognitive mechanisms and decision-making rules may guide both egg recognition and rejection behaviors. Classical optimization models generally assume that decisions are based on the absolute properties of the options (i.e., absolute valuation). Increasing evidence shows instead that hosts' rejection decisions also depend on the context in which options are presented (i.e., context-dependent valuation). Here we study whether the chalk-browed mockingbird's (Mimus saturninus) rejection of parasitic shiny cowbird (Molothrus bonariensis) eggs is a fixed behavior or varies with the context of the clutch. We tested three possible context-dependent mechanisms: (1) range effect, (2) habituation to variation, and (3) sensitization to variation. We found that mockingbird rejection of parasitic eggs does not change according to the characteristics of the other eggs in the nest. Thus, rejection decisions may exclusively depend on the objective characteristics of the eggs, meaning that the threshold of acceptance or rejection of a foreign egg is context-independent in this system.
专性鸟类巢寄生者将卵产在其他宿主物种的巢中，而这些宿主承担了孵化外来卵和养育雏鸟的所有成本。宿主对巢寄生最常见的防御反应是拒绝外来卵。不同的认知机制和决策规则可能指导着卵的识别和拒绝行为。经典的优化模型通常假设决策是基于选项的绝对属性（即绝对估值）。然而，越来越多的证据表明，宿主的拒绝决策还取决于选项呈现的背景（即依赖背景的估值）。在这里，我们研究白眉嘲鸫（Mimus saturninus）拒绝寄生的辉亮牛鹂（Molothrus bonariensis）卵是一种固定行为还是会随窝卵的背景而变化。我们测试了三种可能的依赖背景的机制：（1）范围效应，（2）对变异的习惯化，以及（3）对变异的敏感化。我们发现，嘲鸫对寄生卵的拒绝不会根据巢中其他卵的特征而改变。因此，拒绝决策可能仅取决于卵的客观特征，这意味着在这个系统中，接受或拒绝外来卵的阈值与背景无关。
