ИСТИНА

We investigated the pond searching behaviour of the Marsh frog (Rana ridibunda Pall.) in the population of the west part of Moscow region near Zvenigorod Biological station of Lomonosov Moscow State University. During our experiments we displaced frogs at different distances from their ponds and tracked their movements with the use of mechanical tracking device. The device consisted of a “rucksack” and a sewing machine bobbin with 60 m of thread, which was mounted on the frog’s back. We found that during the breeding period the marsh frogs from Moscow region population (200 ind.) after displacement up to 630 m from their breeding ponds oriented exactly towards their pond, though there was Moscow-river as an alternative water body located at a much shorter distance from the release point. We propose that their good orientation abilities could be explained by the fact that these amphibians are always faced by a problem of searching a breeding pond during spring migrations from hibernation site that are located about a hundred meters away from the pond. To test this hypothesis we investigated pond searching abilities of the marsh frog in the southern population of Utrish (Krasnadar region, Russia). Frogs from this population live in the large mountain lake (210m x 170m) without any other water body within 5 km. These frogs live, breed and hibernate in one water body and do not have any migration activities, that could “train” their orientation abilities. As we propose that frogs from Utrish orient worse than frogs from Moscow population. They didn’t orient towards their lake from the distance of 450 m. However frogs from this population demonstrated interesting sex differences. At the large distance from the lake, where frogs could not orient to the lake, female used strategy of random search and moved very tortuous in all directions. But the males moved straightly in one general direction. Near the lake the differences in the behaviour between males and femaleswere less pronounced: males slightly faster oriented to the water body. The frogs from Moscow population didn’t demonstrate such sex differences: at the large distance from their pond (more than a kilometer) males and females moved tortuously in random directions from the point of release