Variation of age composition and postmetamorphic growth rates in Pelophylax ridibundus (Ranidae, Anura): Comparison populations from Moscow region and Kamchatka

Using skeletochronology, the age composition and growth rates of Pelophylax ridibundus population from the Eastern European part of the native range (Zvenigorod Biological station (ZBS) of Lomonosov Moscow State University, Moscow region) were compared with introduced populations of Kamchatka, differing in the duration of the activity season (T). Both females and males of the ZBS population (T = 5.5 months) reach maturity after the 3rd wintering. This explains the significantly higher averages of the age and body length of both sexes of the ZBS population, in comparison with all Kamchatka populations. Frogs from Kamchatka populations with the same low T (5 months) become mature after the 2nd wintering, and from populations with higher T (from 6 to 10 months) – after the 1st wintering, in the latter case, males more often than females. In Kamchatka populations with relatively high T values, the growth of males begins to slow down earlier than females, this difference explains the significantly larger sizes of females in these populations. In general, the differences between the ZBS population and Kamchatka populations with relatively low T are not as strong as the differences from Kamchatka populations with higher T.