Growth and Development of Pseudomys gracilicaudatus (Rodentia: Muridae) in the Laboratory

Abstract

Information on development (to 40 days) and growth (to adult size) was obtained from 26 litters of Pseudomys gracilicaudatus (Gould, 1845). Animals were laboratory-raised, the breeding stock originating from Myall Lakes, N.S.W. Young are precocial at birth and early development is rapid. Lower incisors have erupted at birth and upper incisors at 1(0-4) day. Head and shoulders are furred at birth and a full pelage is present by 6 days. Ears and eyes open at 9 (7-11) and 11 (9-12) days, respectively. Weaning occurs during the fourth week and the first moult begins at about 30 days. Adults show significant sexual dimorphism (males, 90 g; females; 69 g; P<0.05), which becomes apparent after an age of 1 month. Head length, hind foot length and head + body length do not show significant differences until after an age of 2 months. Growth in the first 40 days is multiphasic, changes in growth rate being related to developmental events. Inverse index of growth (20-90% of adult weight) is 110 days in females and 125 days in males. The rapid early development, which may be related to increasing juvenile survival, contrasts markedly with the slow growth rate.