page_title: Muhalnitsa
section_title: History of the migration
hierarchical_section_title: Muhalnitsa / History of the migration
caption_attribution_description: English: In the height of the breeding season almost all of the water surface is covered with eggs. Български: В разгара на размножителния период почти цялата водна площ е покрита с яйца. Български: Тази снимка е качена по време на създаването на първия уикиград в България WikiBotevgrad. English: This photo was uploaded during the creation of the first wiktown in Bulgaria WikiBotevgrad.
context_page_description: ”Muhalnitsa” is a protected area in western Bulgaria, located at one kilometre south of the town of Botevgrad and at 63 km north-east of the capital Sofia. It is situated in the Botevgrad valley in the western section of the Balkan Mountains. ”Muhalnitsa” was established in 1992 to protect a unique breeding migration of the common frog.
context_section_description: The mass arrival of thousands of frogs in the swamp in the area of “Muhalnitsa” has probably began in the end of the last glacial period, i.e. around 8000 years ago. During this annual breeding migration from their hibernation habitats (rivers and streams in the high parts of the mountain) to the “Muhalnitsa” swamp, the common frogs cover distances of up to 6 km, and some of them probably over 10 km. The breeding season lasts only about two weeks, usually in the end of February or the beginning of March, depending on ambient temperature. Pairs of breeding frogs and deposited eggs among the still melting ice is a common sight. The frogs move down the Zelin River and instinctively know when to leave it in order to reach the swamp. After the end of the breeding season, adult frogs return to the high parts of the mountain by land, covering approximately the same distances. Tadpoles hatch from the fertilized eggs, metamorphose into froglets and leave the swamp by the end of May and the beginning of June. This breeding migration is unique for the species and is among the longest known migrations in the world of amphibians.
caption: In the height of the breeding season almost all of the water surface is covered with eggs.
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