CALGARY - Staff at Edmonton and Calgary zoos are in mourning after both had baby animals die this week.

Officials at the Calgary Zoo are "devastated" after a tiny Siberian tiger cub that was fighting for its life died Thursday night, while at the Valley Zoo in Edmonton, a nine-week-old red panda cub perished the same day.

Calgary staff believe the female tiger cub succumbed to complications from severe head trauma, similar injuries to those suffered by its sibling who died shortly after birth.

The veterinary team at the Calgary Zoo had been working hard to save the cub, whose birth earlier this week came as a surprise. But the cub's odds of survival were rated 50 per cent or less.

"What we've experienced this week is the harsh reality of nature. The fact that one in three cubs dies soon after birth, both in the wild and in captivity, is of little consolation right now," said Dr. Sandie Black, Head of Veterinary Services.

Black said the cub, which was born on Tuesday, had received round-the-clock care but didn't make it through her third night of life.

"From birth, her clinical signs were consistent with head trauma and that is how our veterinary team had been treating her while trying to remain hopeful she would recover," Black said.

Earlier this week Black said it appeared the death of the first cub was the result of an inexperienced mother.

"We believe she picked up and moved the cub inappropriately. This wasn't an aggressive act at all -- just an inexperienced mom. If you think about that image of a cat carrying a kitten around the shoulders -- well, she just hasn't got it quite right yet."

Siberian tigers are considered endangered and the population continues to decline. Census estimates indicate there are fewer than 400 adult/sub-adult Siberian tigers left in the wild.

Zoo officials had been unaware that the mother, named Katja was pregnant until she gave birth.

Black had indicated it was not unheard of for tigers to get pregnant without their handlers knowing.

She said numerous attempts to breed Katja were made last January with a nine-year-old male tiger named Baikal from New York's Bronx Zoo.

"If you think about the relative sizes, our female tiger weighs over 300 pounds -- the cubs weigh less than two pounds each. So they are a very small entity in a very large body. Additionally these are Siberian tigers, (they have) a very thick fur coat," Black said.

"She's a little bit pendulous in the belly and actually there's at least another half-dozen occasions where this has happened in zoos where they haven't been aware of a pregnancy."

Black said it has been a difficult week for zoo staff, especially veterinary and animal care teams who cared for the tiny cub for every minute of her short life and were so excited about her arrival.

Also Thursday, a nine-week old red panda died after it stopped breathing, say officials at the Edmonton Valley Zoo.

"This is a sad and unusual situation," said veterinarian Milton Ness. "I had completed a physical exam on the cub the day prior and she appeared to be thriving."

Ness is waiting for the lab results of the post mortem to determine the underlying medical condition that caused the blood clot.

The red panda cub and her twin brother were born at the zoo on July 5 and both were being hand-raised by the zoo's animal health technologist because the mother tends to overgroom her litters and handle them aggressively, Ness said.

The Edmonton Valley Zoo is home to six red pandas which are part of the international Species Survival Plan. The male panda cub will continue to be hand-raised until the age of four months and fully vaccinated.

There are 800 at zoos around the world but the mortality rate is 50 per cent.

There are only about 8,000 red pandas left in the wild, mostly in the Himalayas in Nepal, Burma and China.

They are an endangered species due to poaching and habitat destruction. They look more like raccoons than the classic chubby black and white pandas.