a–d, Maternal behaviour in TH-overexpression (TH-OE) and control virgin females (nOE = 9, ncontrol = 10). e, Pup retrieval in TH-OE and control postpartum females (nOE = 8, ncontrol = 7). f–h, Pup-directed behaviours in TH-OE and control virgin (g, h) and paternal (f) males. i, j, Inter-male aggression in TH-OE and control males (nOE = 10, ncontrol = 10). Data are mean + s.e.m. *P < 0.05; **P < 0.01, Mann–Whitney U-test.