Figure 1.
Preparatory nesting is a plastic behavior enabled by the elongation of nesting bouts in wake-to-sleep sequences
(A) Nests are scored from 0 to 4 based on their height: 0 to 2 for open nests and 3 and 4 for closed “brooding” nests. Then, 95% of mid-gestational females build brooding nests over 2/3rd of days.
(B) Daily proportions of nest scores in a cohort of C57BL/6NRj mice. After mating, the proportion of preparatory nests increases in both pregnant and pseudopregnant mice. Nest quality returns to baseline in pseudopregnant mice 13 days after mating. ∗Indicates days for which the mean nest scores are significantly different from those in the previous day (p < 0.05, Wilcoxon signed rank test).
(C) Rolling average curve of the mean daily nest score of virgin, pseudopregnant, and pregnant mice, and the mean score calculated for each mice in the first and second weeks of pregnancy is shown.
(D) Event plots of nesting, grooming, and sleep behaviors recorded after the addition of nestlets in virgin and pregnant mice at E15 (each row is a mouse, the first hour after the initiation of nesting is shown). Nesting bouts are longer and occupy most of the active time in pregnant females.
(E) Detail of a wake-to-sleep behavioral sequence in a virgin and an E15 pregnant mice. While the grooming bouts are comparable in both mice, nesting bouts are extended in pregnant females.
(F) Cumulative curve of nest time based on (D). E15 pregnant females initiate nesting sooner and spend more time nesting than virgin females.
(G) Comparisons of the overall uninterrupted nesting time (bouts of 1 min or more) of virgin and pregnant females. E15 pregnant females maintain long uninterrupted nesting bouts. ∗∗ P < 0.01 and ∗∗∗∗ P < 0.0001. Unpaired Mann-Whitney ranked U test (A, F, and G) and one-way ANOVA Kruskal-Wallis test (C). All data are presented as mean ± SEM. See also Figure S1 and Video S1.