Breeding biology, respiration, and larval development of two introduced frogs ( Litoria raniformis and L. ewingi )

Aspects of breeding biology, larval development rates and temperature tolerance, and adult respiratory physiology of the hylid frogs Litoria raniformis and L. ewingi are compared. In Canterbury, the green frog L. raniformis breeds in spring and summer and disappears in winter. Its larvae survived well in the laboratory at 23 ± 2°C but mortality was high at 15 ± 3°C. In contrast, the whistling frog L. ewingi breeds throughout the year in the South Island, and tadpoles had excellent survival at both temperatures. L. raniformis had a larval life‐span of greater than 70 days at 23 ± 2°C, whereas most L. ewingi completed metamorphosis 50–64 days after hatching, at this temperature. During metamorphic climax of L. raniformis , head‐plus‐body length remained nearly constant whilst the tail was resorbed, contrary to a previous report. At 23°C in the laboratory, adult L. ewingi and juvenile L. raniformis of the same size remained alert and had similar rates of oxygen consumption. However, at 7°C L. raniformis became torpid and the mean rate of oxygen consumption was significantly lower than that of L. ewingi. These differences appear at least partially attributable to a relative independence of the effects of cold temperature on pulmonary and buccopharyngeal ventilation frequencies in L. ewingi . It is concluded that a greater tolerance by larvae of cool temperatures and higher oxygen consumption by adults at cold temperatures are adaptations enabling L. ewingi to have a longer breeding period than L. raniformis . In addition, the relatively short life‐span of L. ewingi larvae at warm temperatures may assist the species to breed in both permanent and temporary waters.