Diet composition of the Italian crested newt (Triturus carnifex) in structurally different artificial ponds based on stomach contents and stable isotope analyses

Abstract

In order to evaluate the effects of ecological disturbances, such as climate change, human‐induced habitat modification, or species introduction, and in order to adopt appropriate management policies for their conservation, knowledge of the trophic ecology of protected or threatened species is crucial. The Italian crested newt, Triturus carnifex (Laurenti, 1768), is listed in annexes II and IV of the European Habitats Directive. For this species, changes in water quality and habitat loss represent major threats, potentially impairing its breeding and feeding activities. Artificial aquatic habitats, such as cattle‐drinking pools, represent valuable refuges and suitable breeding sites for T. carnifex. The aim of this study was to determine the food niche of the Italian crested newt in these habitats, evaluating its prey selection strategy in relation to a range of environmental conditions and differing availability of resources. Stomach contents (indicative of short‐term diet) and δ13C and δ15N signatures of tails (indicative of medium‐term diet) of adult newts from three artificial ponds in central Italy, where traditional silvo‐pastoral activities are still important, were determined. Potential prey were also sampled and processed for stable isotope analysis. Triturus carnifex, similar to other newt species, is an opportunistic predator, feeding on a wide variety of prey that includes terrestrial and aquatic macroinvertebrates. In particular, the opportunistic use of temporally available small zooplankton was identified from stomach contents analysis. Conversely, stable isotope analysis highlighted the consumption of larger, soft‐bodied prey that the stomach‐contents‐based approach underestimated. These included terrestrial oligochaetes, which turned out to be the most important and energy‐rich food source in the medium term. These results emphasize the usefulness of combined approaches for studying the trophic ecology of salamanders and also highlight the importance of the integrated management of aquatic breeding habitats and neighbouring terrestrial habitats, as sources of food, for newt conservation.

Truly invasive or simply non‐native? Insights from an artificial crested newt hybrid zone

“…Crested newts may occasionally prey on other amphibians, in particular their eggs and larvae. However, amphibians are not the main prey items for either T. cristatus or T. carnifex (Careddu et al, 2020; Dolmen & Koksvik, 1983; Fasola & Canova, 1992; Iannella et al, 2020; Roşca et al, 2013), meaning that it may make little difference to other amphibians whether the native or the non‐native species, or hybrids co‐occur in the pond. The limited impact of T. carnifex and hybrids on native amphibians may also be evidenced by the rich amphibian fauna at our study sites, with up to seven species per pond, including threatened species such as Bombina variegata and Pelophylax lessonae .…”

Ontogenetic Changes of the Aquatic Food Uptake Mode in the Danube Crested Newt (Triturus dobrogicus Kiritzescu 1903)

“…In case of active movements of the prey after the predator approached it, a new feeding situation could occur and the larvae may lounge a new attack in reaction to the new stimulus. As Triturus adults are known to feed on immobile prey (see Careddu et al, 2020), a topic for further research is the detection of the ontogenetic stage at which the animals switch their mode of reaction concerning the mobility of the prey.…”

Biological Invasions in Fresh Waters: Micropterus salmoides, an American Fish Conquering the World

“…In addition to competing with other fish such as Esox lucius, a native predator of higher commercial value [19,98], the bass has been reported to negatively affect amphibian species of conservation interest [131,207], representing an indirect source of economic loss. Indeed, some of the species affected by bass (e.g., the Italian crested newt Triturus carnifex; [131,141]) are not only important for nature tourism, but are also the subject of funded conservation and research programs, as they are particularly vulnerable to changes in both aquatic and terrestrial habitats [208].…”