Diurnal nursing pattern of wild-type European rabbits under natural breeding conditions

The European rabbit Oryctolagus cuniculus is an important model system in the study of mammalian maternal behavior. This is at least partly due to the rabbit's unusually limited pattern of maternal care, characterized by the mother briefly visiting the young to nurse just once approximately every 24 h. In studies of domestic breeds under laboratory conditions it has been found that females show a rather predictable interval between these once-daily visits. However, as there are reports of considerable inter-individual variation, the aim of our study was to identify factors with the potential to modify the rabbit's diurnal pattern of nursing, such as characteristics of the mother, litter size and also potential changes in the nursing interval length during the early postnatal period. We studied the time course of nursing visits in wild-type rabbits in the natural setting of a large field enclosure in order to obtain results unbiased by laboratory artifacts. Using an automatic portable gas analyzer, we monitored the timing of nursing events by recording the change in oxygen concentration within natural breeding burrows occurring when mothers entered to nurse and calculated the interval length between successive nursing events. During the first nine postpartum days, when our study was conducted, rabbit mothers on average showed a nursing interval of about 24 h. Return intervals remained rather constant in mothers of larger litters but decreased in mothers with smaller litters, resulting in them visiting their young to nurse a little earlier each night. Mothers’ age, day length and season did not affect nursing intervals. In conclusion, our study confirms that under natural conditions rabbits nurse their young only once approximately every 24 h, but that this pattern is not completely fixed and can be modulated by litter size, possibly via the strength of sucking stimulation received by the mother during nursing.