Marked peculiarities in the biology of a species that may be observed, possibly regardless of genetic changes, on the periphery of the species habitat may provide for species survival under extreme conditions. The same may be relevant to populations that are isolated, marginal, or remote from the main distribution range of a species. With this in mind, several biological features of the edible dormouse were studied. This rodent species features a vast distribution range in Europe and partly in Asia. Differentiation into subspecies is mostly not observed within the range. This allows comparing the biology of a single species over significantly distant areas. The range of biotope preferences of the dormice on the periphery of their distribution is wider than in the central areas. In the former cases, these rodents were found in forests featuring a significant proportion of birch and aspen in the forest stand. These observations are similar to those on the northern boundary of the dormouse distribution range in Poland and Lithuania. Some specific features of the diet of the species are associated with these habitats. In the Zhiguli Mts. (Russia) and Lithuania, the main diet includes birch seeds. At the same time, fruits and berries, which are of major importance in the other parts of dormice distribution range, are completely absent among the juicy forages. These differences probably underlie the development of a unique mechanism of reproduction control, which is not observed in other mammalian species. On the periphery of the distribution range, the number of sources of the basic forages for the highly specialized species under study is increased compared to the rest of the distribution area, and the reproductive activity of dormice is annual. However, upon the absence of a sufficient amount of the high-calorie food, mass embryonic resorption in most of females occurs. In addition, in the easternmost population, a higher territoriality is featured by females rearing offspring, and the phenomenon of communal nesting by related females is not observed. To confirm whether the genetic or environmental factors are at the base of the biological features described, large-scale population genetic studies are warranted. At the present stage, field studies allow tracing analogous features in other parts of the species habitat and thus help illustrating the ecological plasticity of the oligophagous species under suboptimal conditions.