Scholarly record

CASES OF MELANISM IN MAMMALS OF YAKUTIA (EASTERN SIBERIA, RUSSIA)

Gennady Boeskorov, Marina Shchelchkova, V. N. Vinokurov

Abstract

Melanism is found in many animal species. This phenomenon is caused by a large amount of melanin pigment and causes an abnormal black or dark brown colour of the outer covers. Melanistic individuals are usually quite rare in nature. However, there are a number of examples indicating that melanistic colouring in animals can be adaptive under certain conditions and be supported by natural selection. These examples include the phenomenon of industrial melanism, described in the birch moth Biston betularia, as well as an increased number of melanists in tropical felines. In other cases, the increase in the number of melanists is not associated with the adaptive value of dark colour, but may correlate with some physiological features of organisms that help them to survive better under certain conditions. This is noted, for example, in the two-spotted ladybeetle Adalia bipunctata, common brushtail possum Trichosurus vulpecula, common hamster ?ricetus cricetus, water vole Arvicola terrestris, etc. There is a trend in the relative increase in the number of melanists in the southern regions. In the north, in Siberia, apparently, melanists are more rare. We have analyzed data on the melanists finds among mammals of Yakutia collecting the questionnaire information from zoologists and hunters and information from scientific literature. Also we studied stuffed mammals in various museums of Yakutia. Individual specimens of melanists were recorded in the northern pika Ochotona hyperborea, Siberian chipmunk Eutamias sibiricus, Arctic ground squirrel Spermophilus parryii, red fox Vulpes vulpes. Several cases of melanists were found in the Yakutia mountain hare Lepus timidus. In this species, which has a pronounced adaptive seasonal dimorphism in the colouring of fur (in winter, as it well known, L. timidusпїЅs fur is of snow-white colour), it would seems that the melanic forms should not be supported by selection and survive in nature. Nevertheless, there are cases of shooting and trapping mountain hares-melanists in various districts of Yakutia (Nyurbinsky, Verkhnevilyuisky, Suntarskiy, Kobiaysky, Megino-Kangalassky) in different years. The peculiarities of the fur colouring of two hares-melanists from the Suntarsky district are described. The fairly regular occurrence of hares-melanists in the Vilyui river basin is discussed, which may indicate a certain advantage of this phenotype. During the autumn hunting before snowfall the dark hares are harder to see than the white ones, that can promote the melanists survival.

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DOI resolver: doi.org/10.5593/sgem2017h/63/s30.142

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