Zepeda José Alfredo, Bautista Amando, Féron Christophe, Martínez-Gómez Margarita, Robles-Guerrero Franco, Reyes Meza Verónica, Hudson Robyn, Rödel Heiko G
Doctorado en Ciencias Biológicas, Universidad Autónoma de Tlaxcala, Mexico; Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Mexico; Preparatoria Alfonso Calderon Moreno, Benemérita Universidad Autónoma de Puebla, Mexico.
Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Mexico.
Physiol Behav. 2023 Mar 15;261:114089. doi: 10.1016/j.physbeh.2023.114089. Epub 2023 Jan 16.
Individual-level sibling interactions in the litter huddle have been studied extensively, especially in the domestic rabbit (Oryctolagus cuniculus). However, little is known about inter-litter differences in pup activity patterns during early postnatal life, in particular regarding the drivers of such variation. In our study on 2-3-day-old rabbit pups, we predicted lower locomotor activity in litters with lower mean body masses on the day of birth (starting body mass) and with lower daily milk intake per pup, possibly constituting a behavioral strategy of pups to cope with associated energetic constraints. For an automatized assessment of pup locomotor activity in the litter huddle, we successfully developed and validated a method based on the quantification of dissimilarities between consecutive frames of video footage. Using this method, we could confirm a U-shaped time course of litter-level locomotor activity, with maximum values shortly before and after the once-daily nursing typical for the rabbit. As predicted, between-litter variation in mean starting body mass and in daily milk intake affected the degree of locomotor activity in the litter huddle, in an interactive way. That is, in litters with heavier starting body masses, pup locomotor activity was greater in pups with an initially higher milk intake, suggesting that only pups with better body condition and a higher energy intake could afford higher levels of activity. This interaction was exclusively apparent during the middle phase of the 24 h inter-nursing interval, when litter activity was low. Shortly before nursing, when pups show higher levels of locomotor behavior in anticipation of the mother's arrival, and shortly after nursing when the pups were more active possibly due to adjustments of their positions in the huddle, activity levels were decoupled from pups' starting body mass and previous milk intake. Our findings highlight the importance of pup body mass and daily energy intake, two parameters known to be related to maternal characteristics, in shaping inter-litter differences in pup locomotor activity.
在同窝幼崽聚堆中的个体水平的同胞互动已得到广泛研究，尤其是在家兔（穴兔）中。然而，对于出生后早期幼崽活动模式的窝间差异知之甚少，特别是关于这种差异的驱动因素。在我们对2至3日龄兔幼崽的研究中，我们预测，在出生当天平均体重较低（起始体重）且每只幼崽每日奶摄入量较低的窝中，幼崽的运动活动会较少，这可能构成幼崽应对相关能量限制的一种行为策略。为了自动评估同窝幼崽聚堆中的运动活动，我们成功开发并验证了一种基于视频片段连续帧之间差异量化的方法。使用这种方法，我们可以确认窝水平运动活动的U形时间进程，在兔典型的每日一次哺乳前后不久出现最大值。如预期的那样，起始体重平均值和每日奶摄入量的窝间差异以交互方式影响同窝幼崽聚堆中的运动活动程度。也就是说，在起始体重较重的窝中，最初奶摄入量较高的幼崽的运动活动更大，这表明只有身体状况较好且能量摄入量较高的幼崽才能承受更高水平的活动。这种相互作用仅在24小时哺乳间隔的中间阶段明显，此时窝内活动较低。在哺乳前不久，幼崽因预期母亲到来而表现出较高水平的运动行为，而在哺乳后不久，幼崽可能因在聚堆中调整位置而更加活跃，此时活动水平与幼崽的起始体重和先前的奶摄入量脱钩。我们的研究结果强调了幼崽体重和每日能量摄入这两个已知与母体特征相关的参数在塑造幼崽运动活动的窝间差异方面的重要性。
