Juvenile socio-ecological environment shapes material technology in nest-building birds

Variation in animal material technology, such as tool use and nest construction, is thought to be caused, in part, by differences in the early-life socio-ecological environment—that is, who and what is around—but this developmental hypothesis remains unconfirmed. We used a tightly controlled developmental paradigm to determine whether adult and/or raw-material access in early life shape first-time nest construction in captive zebra finches Taeniopygia guttata at sexual maturity. We found that juvenile access to both an unrelated adult and raw material of one color led to a majority preference (75%) by novice builders for this color of material over that for either natal-nest or novel colored material, whereas a lack of juvenile access to both an unrelated adult and raw material led to a four- and nearly three-fold reduction in the speed at which novice builders initiated and completed nest construction, respectively. Contrary to expectation, neither the amount of time juveniles nor their adult group-mate spent handling the raw material appear to drive these early-life effects on zebra finches’ first-time nest construction, suggesting that adult presence might be sufficient to drive the development of animal material technology. Together these data show that the juvenile socio-ecological environment can trigger variation in at least two critical aspects of animal material technology (material preference and construction speed), revealing a potentially powerful developmental window for technological advancement. Thus, to understand selection on animal material technology, the early-life environment must be considered.

动物物质技术（animal material technology）的变异，诸如工具使用与巢筑行为，目前被认为部分源自个体早期社会生态环境的差异——即个体周遭的同伴与环境因子，但这一发育假说迄今尚未得到证实。我们采用严格受控的发育范式，旨在明确：性成熟圈养斑胸草雀（Taeniopygia guttata）的首次筑巢行为，是否会受其幼年时期接触成年个体和/或原材料的经历影响。研究结果显示，幼年阶段同时接触非亲代成年个体与单一颜色原材料的实验组，新手筑巢者对该颜色原材料的偏好率达75%，显著高于其对亲代巢材或新颜色原材料的偏好；而幼年阶段未接触非亲代成年个体与原材料的对照组，新手筑巢者启动筑巢与完成筑巢的速度分别下降了四倍与近三倍。与预期相悖的是，幼年个体接触原材料的时长，以及成年同伴处理原材料的时长，似乎均未介导这些对斑胸草雀首次筑巢的早期发育效应，这提示成年个体的存在或许足以推动动物物质技术的发育进程。综上，本研究数据表明，幼年社会生态环境能够触发动物物质技术至少两个关键维度的变异——原材料偏好与筑巢速度，揭示了技术进化中一个潜在的强影响力发育关键期。因此，若要解析动物物质技术所受的选择压力，必须将早期生活环境纳入考量范畴。