A newborn gorilla has died at the Calgary Zoo, despite the attention of her young mother and close monitoring by zoo keepers.

The baby gorilla, who was born 12 days ago at the zoo, died Thursday only an hour after being observed vocalizing and attempting to nurse.

An examination revealed no obvious injuries and zoo officials hope that a post-mortem examination will reveal the cause of death. Results will be available in a few weeks.

Keepers said that when they arrived Thursday morning, the gorilla troop was sitting in a circle around the baby.

The troop is aware of the loss. After the baby died around 5:20 p.m., the troop was given the opportunity to view her post-mortem. Keepers expect the troop to accept the death and return to their normal routine within a few days.

"I found the entire troop sitting around Zuri, and it was very touching actually to see them so comforted and quiet," said keeper Les Stengenga at a press conference.

It was the first baby for the young mother, Zuri. But keepers said they were encouraged by the progress of her mothering skills in the days after her baby was born.

"For the first eight days everything was very good," said Stengenga. "We saw good nursing behaviour; Zuri was well-bonded to the baby."

Officials said on the zoo's website that the infant had experienced considerable stress over several days prior to her death and may have used up the small amount of reserve energy newborns call upon to respond to such stress.

Zuri had gotten into the habit of putting the baby down while she looked for food.

On two of those occasions another gorilla in the troop, a dominant female named Tabitha, picked her up and would not give her back to her mother.

Although the other female allowed the baby to attempt to nurse, she was not lactating so the baby was unable to feed during the hours she was kept from her mother.

That is not uncommon behaviour when a baby is born in a gorilla troop, said zoo keepers.

"The first time Tabitha took the baby on the day of the birth it was actually a somewhat encouraging sign because one of our contingency plans had a surrogate program built in," said Stengenga. "That wasn't our intent and it didn't materialize that way, but it was a good sign."

Keepers had to immobilize the other female to retrieve the baby, however.

The baby was given supplemental feedings in the wake of the incidents, and appeared still strong and vigorous afterward, zoo officials said on the website.

The baby was not observed nursing the day before her death, however, so an additional supplemental feeding was planned for Thursday. But the baby began to exhibit signs of shock shortly before the feeding was scheduled.

Keepers believe the separations and the immobilization of the dominant female may have shaken Zuri's confidence as a new mother and her mothering became erratic.

Before the birth of her baby she was given stuffed animals to hold as baby surrogates, and encouraged to practice maternal instincts. She had even been observed picking up mice and kissing them and patting them and letting them run around on her shoulders.

Although the gorilla exhibit will remain open, visitors over the next few days are being asked to be quiet and stay away from the glass inside the exhibit to give the troop time to adjust to its loss.

"We live and breathe gorillas and it's very difficult. It's a huge hole in our heart," said Stengenga.

Zoo should stop breeding: group

Meanwhile, an animal rights group says the Calgary Zoo should stop some of its breeding programs in light of the gorilla's death.

"I think that they should stop any breeding programs that they're doing where animals are not being returned to the wild," Zoocheck Canada Campaigns Director Julie Woodyer told CTV Calgary. "And specifically, I think they need to re-look at which species they have that they are unable to meet those animals needs."

But the Calgary Zoo says its conservation programs are important to maintain the species.

"(Gorilla) populations in Africa are being decimated, literally cut in half in 20 years . . . in our generation. And in our children's generation, there may be no wild gorillas left," said Stengenga.

According to the Calgary Zoo, the mortality rate for gorillas born in captivity is about 30 per cent, particularly for newborns of first-time mothers. In the wild, the rate is even higher, at around 42 per cent.

With a report by CTV Calgary's Shelley Makrugin