Patterns and predictors of inter-litter differences in rabbit pup locomotor activity, based on an automatized quantification method

• Published in: Physiology & behavior Vol. 261; p. 114089
• Main Authors: Zepeda, José Alfredo, Bautista, Amando, Féron, Christophe, Martínez-Gómez, Margarita, Robles-Guerrero, Franco, Reyes Meza, Verónica, Hudson, Robyn, Rödel, Heiko G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.03.2023
• Subjects: Animals; Animals, Newborn; Behavior, Animal; Body Weight; Early development; Energy allocation; Energy Intake; Female; Litter huddle; Litter Size; Locomotion; Milk intake; Oryctolagus cuniculus; Pregnancy; Rabbits; Siblings; Oryctolagus cuniculus; Energy allocation; Litter huddle; Early development; Milk intake; Siblings
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2023.114089

•We studied inter-litter variation in rabbit pup activity, including its drivers.•Using an automatized method, we confirmed a U-shaped activity pattern along the day.•Locomotor activity was highest in litters with heavy pups with high milk intake.•We suggest that energetic constraints shape locomotor activity in 2–3-day-old pups.•Results may have implications for individual differences in activity within litters. 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.