Postnatal Development in Peromyscus Maniculatus-Polionotus Hybrids. I, Developmental Landmarks and Litter Mortality

Abstract

Newborn laboratory hybrids of Peromyscus maniculatus and P. polionotus were observed daily from birth to weaning and compared with offspring of each of the parent types. The Fi hybrids were intermediate between the parent types in mean age at which pinnae unfolded, hair appeared, and eyes opened. Of the parent types, the pinnae of P. polionotus opened one day later than P. maniculatus. Hybrid offspring were less viable than the parent types, with a mortality peak noted during the second postnatal week.