A polar bear receives it's Christmas treat at Toronto Zoo on Sunday December 26, 2010. Toronto Zoo announced Wednesdaythat one of their two, 10 year old female polar bears, Aurora, gave birth to three cubs overnight.Chris Young/The Canadian Press
A second newborn polar bear cub has died from wounds inflicted by its mother at Toronto Zoo, while a third remains in intensive care.
The triplets, two males and a female, were born prematurely Tuesday night to 10-year-old Aurora. Shortly after the birth, Aurora attacked her cubs, killing one and leaving a second injured. The other male was unharmed.
The second hurt cub died Thursday. The survivng male is still being surveyed around the clock and will be hand-raised.
Aurora is still on display, along with the zoo's two other polar bears, a male and female.
Polar bear cubs are typically born between November and January, making the Oct. 11 birth the earliest recorded in captivity, the zoo says.
The cubs' birth is significant because polar bears have slow reproductive rates for terrestrial mammals, with females typically producing five litters in their lifetime, often with no more than two cubs a litter.
Polar bear cubs are usually born between November to January. The Toronto cubs' Oct. 11 births make them the earliest recorded birth of polar bears in captivity, the zoo said.
One of the most famous polar bear born in captivity was Knut, who died this spring at the Berlin zoo, where he had spent all four years of his life.
Knut and his twin brother had also been rejected by their mother at birth. The brother died after a few days but Knut survived, thanks to constant feeding from his zoo caregivers.
Animal-rights activists say that his death last March stemmed from the trauma of living in confinement. The Berlin zoo said he would have survived his encephalitis but for the fact that the brain swelling made him fall into his enclosure's pool, where he drowned.