Abstract
Though newts are exclusively carnivorous predators, non-prey items (silt, plants, skin sloughs) also have been found in their stomachs. There are no previous studies on this topic apart from casual reports.
We conducted a dietary study of Alpine newts (Mesotriton alpestris) at two localities in the Czech Republic, focusing on the influence of sex, locality, month, and weight of digested prey on consumption of non-prey items. Localities were two fishless ponds (surface area < 40 m(2), depth < 1 m) at an elevation of about 450 m.
Both ponds were isolated from other water bodies and inhabited also by Smooth newts (Lissotriton vulgaris L.) and Common frogs (Rana temporaria L.). Newts were captured by net from the shores and stomach contents were extracted using a stomach flushing technique.
We sampled 190 individuals. At least one non-prey item (i.e. silt, plants, skin sloughs) was found in 44% of newts' stomachs.
The most numerous items were plant fragments. The weight of consumed prey did not affect the presence of non-prey items in stomachs of newts.
Locality (probably relating to prey availability) affected frequency of newts with plants and silt in their digestive tracts, but skin sloughs were consumed at both localities with the same frequencies. All non-prey items were consumed mainly at the beginning of the breeding season (year 1997) and with no difference in frequencies between males and females