They were born weighing less than a bag of sugar and not expected to survive. But now, on their 100th-day birthday these twin polar bears are thriving and finding time to play a ball game or two. They were born on March 5 and, to give them the best chance of survival, keepers at Tianjin Haichang Ocean World in northern China placed them into incubators.They were born weighing less than a bag of sugar and not expected to survive. But now, on their 100th-day birthday these twin polar bears are thriving and finding time to play a ball game or two. They were born on March 5 and, to give them the best chance of survival, keepers at Tianjin Haichang Ocean World in northern China placed them into incubators.