Huddling is considered as a social strategy to reduce thermal stress and promote growth in newborn altricial mammals. So far the role of huddling on the allocation of the saved energy has not been quantified nor the related impacts on body temperature rhythms. To determine the energy partitioning of rabbit pups either raised alone or in groups of 8, 4 or 2 individuals, when thermoregulatory inefficient (TI) and efficient (TE), we first investigated their total energy expenditure and body composition. We then monitored body temperature and activity rhythms to test whether huddling may impact on these rhythms. Pups in G8 utilized 40% less energy when TI than did pups alone and 32% less energy when TE. Pups in G8 and G4 had significantly lower thermoregulatory costs in the TI period, whereas pups in G2, G4 and G8 had lower costs during the TE period. Huddling pups could therefore channel the energy saved into processes of growth, and accrued more fat mass (on average 4.5±1.4g) than isolated pups, which lost 0.7g of fat. Pups in G4 and G8 had a body temperature significantly higher by 0.8°C than pups in G2 and G1 when TI, whereas no more differences were noted when TE. Moreover, pups alone showed an endogenous circadian body temperature rhythm which differed when compared with that of huddling pups, with no rise before suckling. Huddling enables pups to invest the saved energy into growth, and to regulate their body temperature in order to be more competitive during nursing.