Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 3. (Budapest 1953)

Éhik, Gy.: The occurrence of the Root-vole (Microtus oeconomus Pall.) at the Kisbalaton

The Occurrence of the Root-vole (Microtus oeconomus Pall.) at the Kisbalaton By G y. É h i k, Budapest M. Vasvári (4), during a lecture held in the Hungarian Zoological Society, mentioned that he found the remains of Microtus oeconomus in the crops of the Rough-legged Buzzard and the Marsh Harrier shot around Keszthely. Vasvári did everything he could to get the living animal in the city's vicinity, till the autum of 1944. His researches were cut short by his death. During the first afterwar years we had a thousand other troubles than to continue investigation on this animal. It happened in the spring of 1950, when the Museum of Natural History of Hungary planned to make a faunistic survey of the Kisbalaton, that A. K eve, of the Ornithological Institute, called my attention to Vasvár i's interrupted researches. 1 was glad to get new data on oeconomus. The question of its occurrence in our country had since long occupied my thoughts but incognizant of its habitats I have not been able to capture it with my own hands even around Rajka. Undoubtedly, this was the reason why the investigations of our ornithologists were in vain, though led during many years, around Keszthely. V a s v á r i's data referred to the Kisbalaton and its environments, so I took up the task with the greatest expectations. My first excursion to the Kisbalaton was on the 31 May, 1950. The first probings into the territory were unsuccessful but I went forward step by step to look up always new biotops. Nothing else but the core of the dense reed jugle remained on the seventh day. Extreme dryness, however, made it possible to go deep into its middle. There was no water in the many hundreds meters deep reed, though ground water seeped up under our steps. Undergrowth flourished in unbelievable masses everywhere. We had to cut through in sometimes 2—3 meters high nettle.bushes. But here, in this waterless though densely undergrown humid reed jungle our Root-vole (Microtus oeconomus Pall.) lived. I succeeded to trap the first three specimens, 6 June, 1950. During my other excursions my main duty was to try and establish the animal's distribution. I trapped in the Kisbalaton reservation everywhere and succeeded to put beyond dispute the fact that the animal may be found everywhere in the waterless but densely undergrown humid reeds of the reservation, f have never found it in absolutely dry and isolated smaller reeds nor in the neighbouring dry grassy meadows or in the cultured fields which border on the high reeds in some places. This at least was the situation in 1950, a very dry year. But 1951 was the year of a great inundation on the Kisbalaton. Water stood so high that the small isle Diás could only be reached on foot in the autumn. Into the inundated territory, lacking suitable equipment, I had not been able to enter and so could trap only around the edges of the water. This was the time when Í observed that oeconomus, out of sheer need, invaded also the humid though waterless parts touching on the flooded areas, settling on higher and densely grown places or shrubby hillocks emerging from the wet localities. Our experiences gained during two years seem to prove that the animal closely follows the moving of water and has its habitat with the greatest preference near it in dense and wet reeds rich in undergrowth. 1950 was the proliferous year of oeconomus on the Kisbalaton ; many could be had by trapping. A big part of the animals became scabby in the autumn, a consequence of too dense populations. The rather weak trapping results of 1951 cannot be compared with the outstanding ones of 1950, because I was not able to