The normally ferocious Russian winter, the bane of invaders from Napoleon to Hitler, has been unusually mild this year with temperatures hitting record seasonal highs.
"For a second day we are organising extra observation of a female black bear, which has woken up because of the warmth," a spokesman for the zoo in Russia’s second- largest city of St Petersburg told the agency.
"The zoo’s brown bear hasn’t gone to sleep this year."
Temperatures in European Russia are forecast to fall by the end of this week, and return from a current balmy 6 degrees Celsius (43 degrees Fahrenheit) to below freezing.