Article

Why do heavy littermates grow better than lighter ones? A study in wild and domestic European rabbits.

Department of Animal Physiology, University of Bayreuth, D-95440 Bayreuth, Germany.
Physiology & Behavior (impact factor: 2.87). 08/2008; 95(3):441-448. DOI:10.1016/j.physbeh.2008.07.011
Source: PubMed

ABSTRACT Birth mass can vary considerably among mammalian littermates. Heavier pups often show higher growth rates than their lighter siblings, which might positively affect fitness-relevant parameters during later life. Such a correlation between birth mass and pre-weaning growth within litters was confirmed by our study of wild-type and domestic European rabbits (Oryctolagus cuniculus) living in a semi-natural environment and under laboratory housing conditions, respectively. Our study indicates that at least two main mechanisms account for this relationship in our study species: heavier pups had a higher milk intake and also showed a more efficient conversion of milk into body mass. Furthermore, our study suggests that the better milk conversion by heavy pups was driven by three synergistic mechanisms: heavier pups had comparatively more huddling partners in the nest, they did not need to perform large amounts of proactive behavior in order to reach and remain in a central position within the litter huddle, and they could maintain a comparatively higher body temperature most probably due to their more favorable surface area to volume ratio. In conclusion, our study of European rabbits provides strong evidence that both under natural conditions and in the laboratory, within-litter differences in birth mass are maintained and may even increase during pups' early postnatal development.

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Keywords

Birth mass
 
body mass
 
efficient conversion
 
favorable surface area
 
fitness-relevant parameters
 
heavier pups
 
heavy pups
 
higher body temperature
 
higher growth rates
 
higher milk intake
 
laboratory housing conditions
 
large amounts
 
litter huddle
 
milk conversion
 
Oryctolagus cuniculus
 
pre-weaning growth
 
pups'
 
strong evidence
 
synergistic mechanisms
 
two main mechanisms account