Growth of Nestling and Juvenile Platypuses (Ornithorhynchus anatinus).
Body lengths and bill dimensions were recorded from 26 nestling platypuses from various museum collections and from published records. In nestling platypuses less than 3 months old bill width was greater than length, but this was reversed in older nestlings and in juveniles of both sexes. Nestlings grew from a body length of approximately 5 cm (~ 1 week of age) to 34 cm (14-17 weeks). Comparative data on growth of captive nestlings while sparse, supported the general trends seen in nestlings collected for this study. Body lengths and weights were also recorded from 219 (113 female; 106 male) platypuses which had been captured initially as juveniles in the upper Shoalhaven River. New South Wales. Recaptures resulted in 358 separate (215 female; 143 male) records from these animals. At emergence from the breeding burrow in January/February, juvenile males were significantly larger than females. Juvenile males had a mean body length of 41.2 (S.D.± 2.8) and females 37.5 (S.D.± 2.0) cm respectively (p<O.OOI) and mean body weights of recently emerged juvenile males and females were 779 (S.D.± 127) and 588 (S.D.± 88) g (p<O.OOI). Mean lengths and weights of the emerged juveniles were significantly smaller (p<O.OOI) than those sampled as adults (weight 65-70%; length 83-87%). The wide variation in weights and lengths of juvenile individuals of both sexes at first capture may be due to different times of emergence and/or the effects of different litter sizes.