HMM of Maternal Behavior Figure 1. Observed maternal behavior in inbred and reciprocal hybrid mothers. Daily observations of maternal behavior from birth to weaning revealed significantly increased frequency of (A) time in nest, (B) licking/grooming pups, and (C) arched-back nursing by C57BL/6 vs. BALB/c mothers. For reciprocal hybrid mothers, significantly increased (E) licking/grooming pups, but not (D) time in nest, or (F) arched-back nursing was seen in B6xC vs. CxB6 mothers (C57BL/6, N = 26; BALB/c, N = 26; B6xC, N = 36; CxB6, N = 39; * P,0.05, ** P,0.01, *** P,0.001). doi:10.1371/journal.pone.0014753.g001 Table 1. Frequency of observed maternal behaviors in inbred and reciprocal hybrid mothers. BEHAVIOR Arched-back nursing Blanket nursing Licking/grooming pups Self grooming (in nest) Sniffing nest Self grooming (out of nest) Sniffing cage Eating Carrying pup Moving pups Nest Bulding Sniffing pups Drinking Rearing Digging Carrying tail Climbing Arched-back nursing (,half litter) Licking/grooming pups (,half litter) Blanket nursing (,half litter) Sleeping C57BL/6 BALB/c F (1,50) P-value B6xC F(1,75) P-value 0.312±0.025 0.158±0.021 25.049 0.001 0.270±0.028 0.428±0.028 15.763 0.001 0.137±0.007 0.045±0.003 150.853 0.001 0.01460.002 0.01960.003 1.731 n.s. 0.029±0.003 0.012±0.001 31.594 0.001 0.02960.007 0.02660.003 0.128 n.s. 0.05260.004 0.06760.006 3.853 n.s 0.079±0.005 0.119±0.007 21.747 0.001 0.001±0.000 0.000±0.000 6.683 0.013 0.002±0.000 0.006±0.001 17.920 0.001 0.01260.002 0.01060.001 0.506 n.s. 0.01060.001 0.01260.001 0.786 n.s. 0.01560.002 0.02160.002 4.021 n.s. 0.006±0.001 0.012±0.001 9.479 0.003 0.016±0.002 0.039±0.005 15.640 0.001 0.00660.001 0.00860.002 0.778 n.s. 0.00860.002 0.00660.002 0.884 n.s. 0.00060.000 0.00160.000 1.207 n.s. 0.00060.000 0.00160.000 1.859 n.s. 0.00060.000 0.00460.004 1.337 n.s. 0.000 ± 0.000 0.011 ± 0.038 7.989 0.007 0.36360.021 0.20660.024 0.130±0.006 0.02260.002 0.00760.001 0.03160.002 0.07160.004 0.08560.005 0.00060.000 0.00160.000 0.00760.001 0.005±0.001 0.02260.001 0.00660.001 0.01460.002 0.00260.000 0.00660.001 0.00160.000 0.00060.000 0.00160.000 0.01760.003 CxB6 0.41660.020 0.17260.018 0.091±0.004 0.02660.002 0.00960.001 0.03460.003 0.07360.004 0.08360.004 0.00060.000 0.00260.000 0.00660.001 0.010±0.001 0.02060.002 0.00760.001 0.01560.002 0.00360.001 0.00360.001 0.00060.000 0.00060.000 0.00160.001 0.02660.004 3.392 1.357 30.306 2.498 2.672 0.698 0.090 0.088 0.947 0.383 0.187 17.214 0.832 1.193 0.154 1.133 3.092 2.243 0.057 0.095 2.683 n.s. n.s. 0.001 n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. 0.001 n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. Mean frequencies (6 SEM) of an ethogram of twenty-one observed maternal behaviors for C57BL/6 vs. BALB/c (left) and B6xC vs. CxB6 (right) mothers. Behaviors were scored once each minute for two non-contiguous hours each day from postnatal day 1 to 7. Statistical significance was calculated by univariate ANOVA and significant differences (P,0.05) are indicated in bold. doi:10.1371/journal.pone.0014753.t001 PLoS ONE | www.plosone.org 4 March 2011 | Volume 6 | Issue 3 | e14753