Variation in age structures in a subdivided population of Triturus cristatus

Changes in age structure of local populations were analyzed to determine the migrations of adult crested newts (Triturus cristatus) in a network of ponds. An individual's age was estimated by applying a skeletochronological method to the phalanges. The local populations studied bred in four neighbouring cattle ponds, the distance between any two of which did not exceed 150 m. These ponds belong to the larger network. Though the size of the whole population doubled from one year to the next, one local population became extinct due to lack of recruitment of young breeders. The larger local population attracted not only young breeders but also older newts, which probably came from other ponds. In ponds inhabited by fish, the newts were mainly young animals (2–3 years old), suggesting that they leave such ponds after their first breeding season. The results are discussed with regard to the model proposed by Gill for metapopulations of Notophthalmus viridescens. In the crested newt, contrary to Gill's predictions, all the sites do not recruit young breeders, and fidelity to the breeding site may be broken. The two species differ in longevity and age at maturity, hence it is suggested that functional models of metapopulations must integrate life-history parameters.