Predation and Competition Within an Assemblage of Larval News (Triturus)

The impact of crested newts (Triturus cristatus) on the smaller-bodied palmate and smooth newts (T. helveticus and T. vulgaris) was studied during the larval stages using a combination of field and laboratory experiments. In pond enclosures T. cristatus larvae had no effect on the two smaller species over the first four weeks of development. By eight weeks, however, T. cristatus had achieved a size advantage which enabled it to eliminate T. helveticus and severely reduce T. vulgaris by predation. In laboratory trials under food-limited conditions, T. helveticus and T. vulgaris were slightly smaller when raised with T. cristatus, suggesting that this predatory effect was complemented by interspecific competition during early development. Predation of the smaller species started when T. cristatus reached a threshold size of c. 27 mm. No reciprocal effects on T cristatus growth or survival were observed. Although T. cristatus may be a significant predator of congeneric species in natural ponds, other factors, such as differences in microhabitat selection, higher-order predator-prey interactions, and the occasional desiccation of pond habitats may facilitate coexistence between the species.