Immune challenge induces terminal investment at an early breeding stage in female zebra finches

The ‘terminal investment’ hypothesis proposes that individuals with low future survival prospects will gain from increasing investment in the current reproductive event even though it will reduce the chances of future reproduction even further. Such investments have previously been found to occur mainly during the late stages of the breeding event, i.e., encompassing a short period of elevated parental care close to offspring independence. Our aim was to study if a simulated mild bacterial infection can induce a terminal investment already at egg laying (i.e., at an early breeding stage). Therefore, we challenged female zebra finches (Taeniopygia guttata) prior to egg laying with a tetanus-toxoid vaccine mimicking a bacterial infection. Immune-challenged females increased the total clutch mass by 20 %, primarily through laying clutches that were 17 % larger than control females. Although the immune-challenged females produced more eggs, they kept the same investment strategy in relation...“终端投资（terminal investment）”假说提出，未来生存前景不佳的个体，即便会进一步降低未来繁殖的概率，仍可通过提升当前繁殖事件中的投入来获益。此前的研究发现，这类投资行为主要发生在繁殖事件的后期阶段，即子代接近独立、亲本抚育强度短暂升高的时期。本研究旨在探究模拟轻度细菌感染是否能在产卵阶段（即繁殖早期）诱发终端投资行为。为此，我们在产卵前使用模拟细菌感染的破伤风类毒素疫苗，对雌性斑胸草雀（Taeniopygia guttata）进行免疫刺激。经免疫刺激的雌性个体的总窝卵质量提升了20%，这主要源于其产下的窝卵数量较对照组雌性高出17%。尽管经免疫刺激的雌性个体产下的卵更多，但它们在相关方面仍保持了一致的投资策略……