The impact of recent logging and pond isolation on pond colonization by the frog Crinia signifera

Abstract

A colonization experiment was used to investigate landscape use of a commercially managed wet forest in southern Tasmania by the ground-dwelling frog, Crinia signifera. Replicated artificial ponds were placed at increasing distances (20, 100, 250 and 500 m) from nine permanent breeding sites to investigate the effect of pond isolation on colonization. Four of these permanent breeding sites were surrounded by coupes that had been logged within the previous five years and five permanent breeding sites were surrounded by unlogged forest to investigate the effect of recent logging on colonization. The rate of colonization, the frequency of colonization, male size and female size (inferred from clutch size) were monitored over two breeding seasons. No pond isolation effects were found, indicating that G. signifera is randomly distributed throughout the forest landscape for up to 500 m around each permanent breeding site. Such patterns of forest habitat use indicate that management prescriptions should not only take into account the habitat characteristics of breeding sites but should also consider the surrounding terrestrial landscape. Ponds surrounded by unlogged forest were colonized almost two times faster than ponds surrounded by logged forest indicatlng that landscape modtfication can significantly alter amphibian mobility. These findings have consequences for total reproductive output especially in landscapes where breeding sites are highly variable and for species that are slow to colonize new breeding sites.