Discriminant analysis of sexual dimorphism in morphological traits of African Muscovy ducks

Sexual dimorphism was examined in 221 randomly selected adult African Muscovy ducks extensively reared in north central Nigeria using univariate and multivariate measures of body size and skeletal proportions. The body parameters investigated included body weight, 8 primary linear body measurements [breast circumference (BTC), thigh circumference (THC), body length (BDL), bill length (BLL), neck length (NKL),foot length (FTL), total leg length (TLL) and wing length (WNL)] and 4 morphological indices (massiveness, stockiness, long-leggedness and condition index). The univariate analysis showed male dominance (p<0.05) in all the morphometric measurements, with the exception of stockiness and longleggedness where significantly higher mean values were recorded for females. Low, moderate and high positive and negative correlations among the body size and shape characters of the ducks were recorded. The canonical discriminant analysis on body weight and primary linear body measurements revealed that wing length was the most discriminating variable between the sexes, followed by body weight, neck circumference, total leg length, body length and foot length respectively. Three other variables not qualified to enter the model were expunged. The single discriminant function obtained (D= -3.116 + 0.280WNL+ 0.921BWT + 0.191NKL - 0.196TLL 0.063BDL - 0.283FTL) correctly classified 91.4% of individuals of known-sex ducks. This might aid in ecological studies, conservation and improvement of the indigenous ducks.