Maternal investment and maternal care provided by mammalian females can change during their ontogeny. Differences may be related to the age and/or experience (parity) of the female. Several hypotheses have been postulated to explain changes in the rate of maternal care of females during their lifetime. The residual reproductive value hypothesis supposes a higher rate of maternal care in older and more experienced females, in contrast the targeted reproductive effort hypothesis predicts lower levels of maternal care in older and/or more experienced females. To test these hypotheses we investigated nursing bout frequency and time devoted to nursing as predictors of the rate of maternal care, and rate of successful nursing bouts as a predictor of maternal investment, in captive giraffe (22 females, 47 calves in four zoos). We also considered the high rate of allonursing (nursing of non-filial calves) which appeared in all herds. The nursing and allonursing bout frequency as well as the total time devoted to nursing and allonursing increased with increasing parity and age of the female, thus supporting the residual reproductive value hypothesis. In addition, maternal experience of individual females in terms of parity rather than age was responsible for variation in maternal behaviour. This suggests that variation depends on individual experiences.

中文翻译：

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有经验的长颈鹿母亲的产妇保健和耐受性更高

雌性哺乳动物提供的产妇投资和产妇护理在其个体发育过程中可能会发生变化。差异可能与女性的年龄和/或经验（同等）有关。已经提出了几种假设来解释女性一生中产妇护理率的变化。剩余生殖价值假说假设年龄较大和经验丰富的女性的产妇护理率较高，相反，有针对性的生殖努力假说预测年龄较大和/或经验更多的女性的产妇护理水平较低。为了检验这些假设，我们调查了圈养长颈鹿（22头雌性，四个动物园的47头犊牛）中作为产妇护理率预测指标的护理周期和护理时间，以及作为产妇投资预测指标的成功护理周期的比率。我们还认为在所有牛群中都出现了很高的变态反应率（非孝犊的护理）。哺乳和异象抚育的频率以及用于哺乳和异象抚育的总时间随着女性同等年龄和年龄的增加而增加，从而支持了剩余的生殖价值假说。此外，个别女性的孕产经验（按性别而不是年龄）是孕产妇行为变化的原因。这表明差异取决于个人经验。个体女性的产前经验而不是年龄，是造成产妇行为差异的原因。这表明差异取决于个人经验。个体女性的产前经验而不是年龄，是造成产妇行为差异的原因。这表明差异取决于个人经验。