A comparative assessment of growth curves as estimators of male and femaleontogeny in Oryzomys albigularis

We analyzed growth of the sigmodontine rodent Oryzomys albigularis under la boratory conditions, fitting data to growth models, to test the null hypoth esis that no differences exist between sexes. We propose a biologic criteri on for growth-model selection, under the assumption that the curve should s how critical stages of the organism's postnatal development and growth. Fol lowing this approach, growth of O. albigularis best fits a logistic curve. Our results show that, although males and females grow at the same rate, th e final size is significantly different, being slightly dimorphic. These re sults, together with behavioral observations of the animals in the laborato ry, support the hypothesis of a monogamic mating system for this species.