Dr. Fűköh Levente szerk.: Malakológiai Tájékoztató 13. (Eger, 1994.)

MIENIS, H. K.: Prédation on landsnails by the green toad Bufo viridis near The Nesher-ramla Sewage Reservoir, Israel

Prédation on landsnails by the green toad Bufo viridis near The Nesher-ramla Sewage Reservoir, Israel H.-K. Mienis Abstract: On 14 occasions landsnails were encountered in faecal pellets of Green toads Bufo viridis caught near the Nesher-Ramla sewage reservoir in Israel. Remains of the ground-dwelling Hygromiid snail Monacha obstructa were present in each pellet containing snails. Three juveniles were even still alive when extracted from the faeces. A single adult specimen of Euchondrus septemdentatus was also encountered. The Green toad is now known to feed on at least 8 species of landsnails in Israel. Key words: Amphibia, Bufo viridis, prédation, Mollusca, Gastropoda piilinonata, Israel. Introduction Green toads Bufo Viridis Laurenti, 1768 are considered common predators of landsnails and slugs in Israel (Amitai, R 1980). However, the only information concerning more specific cases of landsnails eaten by Green toads was published by Mienis (1987 & 1993). He reported respectively on the extraction of the remains of six species of snails from faecal pellets of these toads in Kibbutz Netzer Sereni and on the find of a living juvenile specimen of Monacha obstructa (Pfeiffer, 1842) in toad-faeces collected near the sewage reservoir of Nesher-Ramla. It was assumed that Bufo viridis, as an opportunistic snail eater, would predate on additional species in other areas of its distribution. The discovery of a relatively large toad population in a restricted swampy area near the Nesher-Ramla sewage reservoir gave a possibility to carry out additional observations concerning this subject. Material and Methods Green toads were cought regularly from February 1993 until February 1994 near an artificial pool cq swampy area caused by a leaking waterpipe just behind the barns of the fieldcrop division of Kibbutz Netzer Sereni near the Nesher-Ramla sewage reservoir. Each animal was kept in a large glass jar until it produced a faecal pellet. This occurred usually within 12-24 hours. No animal was kept for more than 48 hours. All the toads were released afterwards in the same area where they had been caught. Each faecal pellet was placed in a sieve with a mesh size of 0.5 mm and thoroughly rinsed with tapwater. The particles left behind in the sieve were screened for remains of shells under a binocular. The shell fragments were identified by comparing them with a selection of adult and juvenile snails found in the same area where the toads had been caught. Results In 14 faecal pellets the remains of a total of 30 landsnails were encountered. They are enumerated in table 1. Discussion and Conclusion The study of faecal pellets of Green toads caught near the sewage reservoir of Nesher-Ramla confirmed the results obtained previously during a similar study carried out in Kibbutz Netzer Sereni (Mienis, H. K. 1987). Snails were only encountered in pellets during the months that the prey was crawling actively around on the ground i.e. during the rainy period in winter and early spring. Juvenile specimens of Monacha obstructa were eaten without breaking the shell, however, in half-grown specimens the shells were crushed with the mandibles prior to being swallowed.