Maternal behavior in New Zealand white rabbits: quantification of somatic events, motor patterns, and steroid plasma levels.

Several parameters associated with maternal behavior were quantified under laboratory conditions in New Zealand white rabbits. Digging behavior appeared earliest (8-6 days prepartum), its decline preceding the onset of straw carrying (3-1 days prepartum). Hair pulling consummated the construction of the maternal nest. Food intake significantly decreased on days 2 and 1 prepartum. On parturition day, all females spent 300-500 s with the litter while, for the rest of lactation, nursing bouts lasted 199 +/- 7 s. Milk yield increased linearly up to lactation day 19, declining thereafter. Pup weight increased linearly throughout lactation despite the decline in milk yield. Plasma estradiol (E) levels did not significantly vary across pregnancy: 60 +/- 2 pg/ml (days 10-25) and 75 +/- 6 pg/ml (day 30). The testosterone (T) levels at these times were: 200 +/- 10 and 308 +/- 0.03 pg/ml, respectively. Testosterone significantly declined from pregnancy day 30 to lactation day 1 (202 +/- 0.02 pg/ml). Progesterone (P) levels significantly declined from pregnancy day 20 (9 +/- 1 ng/ml) onwards. Progesterone levels were negligible across lactation. Thus, mother rabbits display a sequence of motor patterns and somatic events correlated with changes in plasma levels of T and P against a background of E.