Why Beavers Survived In The 19th Century

Russian scientists give an explanation for the wonder of beaver survival throughout the 19th century, when these animals were badly endangered and lived in conditions that would be fatal for another mammalian species.

A population of beavers can survive, if it includes only three animals living together. Such a small size of viable population is explained by the genetic adaptation of beavers to inbreeding. Beaver genome and behaviour account for an outstanding viability of this species, as is established by A.N. Milishnikov and his colleagues from the Severtsov Institute of Ecology and Evolution in Moscow.

Beavers have a rather puritan character: as distinct from other mammalian species, they don’t give way to promiscuity, but live as couples and even families. Several families make up a settlement (colony) that is a larger society of beavers. However, families maintain their genetic isolation and do not interbreed. Each family resides within a certain area of a river and bank, where the others cannot enter (trespassers are severely punished).

In every family, only one couple breeds, and their offspring stay with them for a long while and don’t breed. Young beavers can make up a couple once they find a suitable place on the river for their own family lodge. Obviously, beavers possess a huge reserve of genetic diversity in order to avoid the negative consequences of inbreeding.

Russian scientists have revealed that genetic differences between beavers within the same colony are stronger than those between representatives of different colonies. A beaver chooses a mate not haphazardly. This was for the first time discovered in the course of captive breeding, which was rather unsuccessful: most animals refused to mate and behaved aggressively to each other.

Only very few couples were happy and lived together for many years. The scientists do not yet know how beavers choose their mates. Apparently, it is somehow connected with the need to avoid genetic similarity.