English to Russian Art/Literary Zoology

Как наиболее точно и лаконично перевести данную фразу в следующем контексте?

Competition for mates is intense. It takes almost three years for polar bear mothers to wean their cubs, so each spring only around a third of them will be free of child-rearing responsibilities and open to breeding. It seems that those who are available are rather free with their favours. Polar bear litters average two or three cubs, and recent research suggests that they can have different fathers because of a delay between impregnation and the implantation of the embryo.

To read more, go to:
http://www.dailymail.co.uk/news/article-2052677/How-polar-be...

If interested, you can watch this documentary at:
http://www.bbc.co.uk/iplayer/episode/b00zj1q5/Frozen_Planet_...