Tigers debut at zoo

For two months, all the three tiny tiger cubs knew of the big, wide world was the inside of their den.

Then, a few weeks ago, a door opened onto a view that was grassy and leafy and green. They approached, then froze.

Gradually, they learned their way around the Philadelphia Zoo's baby-proofed outdoor exhibit, with its drained pool and dry stream.

Eventually, small groups of volunteers and donors came - partly to sneak a peak, partly to acclimate the cubs to people.

This morning, after a 10 a.m. date with the press, they will face another challenge: their debut before a horde of humans.

And the zoo will find out whether the 3-month-old Amur tigers, a highly endangered species, are fierce little guys - or scaredy-cats.

Still in protective custody yesterday, the cubs trotted confidently across the grass, stalking each other, attacking their mother, swatting at weeds, and occasionally tumbling off high rocks.

Every now and then they paused, noses to the exhibit glass, to look quizzically at a handful of humans on the other side.

The cubs - born at the zoo 12 weeks ago today - already have survived a number of potential pathogens and other problems. (In Chicago, two Amur cubs in a recent litter of four died within days of their birth, and their mother ate them.)

"I think this is the point where we finally take a breath," said keeper Kay Buffamonte. She and Tara Brody, the tigers' main keeper, have been tense since their birth, noting every detail, on the alert for problems.

Never mind that today is a big step for the cubs: "This is a big step for us," Buffamonte said.

The size of squirrels when they were born, the cubs now are about twice the size of house cats. Their last weigh-in measured 15 to 18 pounds, but assistant curator of carnivores Chris Waldron is certain they're much heavier, and gaining fast.

They've been gulping down a quarter-pound or more of steak every day - and still nursing.

Lately, they've been most active mornings. What looks like play is actually training for skills they would employ as adult hunters in the wild, said Andy Baker, the zoo's vice president for animal programs.

By early afternoon, they've usually gone inside to nurse and nap by their mother, Kira.

Initially, the staff thought all three cubs were males. But they couldn't get close enough for a thorough examination. Now, they think one is female. She's stayed slightly smaller, and her face is a wee bit rounder.

That would be Terney (pronounced TIER-nee), named for a town in eastern Russia that was the base of operations for a tiger conservation project.

Koosaka (Koo-SAH-kah) means "biter" in Russian, according to the zoo's Ukrainian plumber, who joined in the naming process.

Changbai (Shang-BYE) is named for a tiger reserve in northern China that the cats have started to repopulate.

To human eyes, they are almost identical. Zookeepers tell them apart by the marks over their left eyes: Terney has a sideways v. Koosaka's brow mark looks like a capital K. Changbai's resembles an upper-case L.

Why not easy names, like Frank and Mike?

Wild Amur tigers live along the Russia-China border, and the keepers wanted names to reflect their heritage. Estimates hold that there are 420 Amur tigers left in the wild. Nearly as many live in zoos, including 147 in North America.

In the last year, tiger pairs in the United States and Canada had seven litters of 16 cubs, only nine of which survived. Oddly enough, the overall survival rate in captivity is virtually the same as in the wild - roughly 30 percent.

In a breeding program over the last two decades, North American zoos have produced as many cubs as there are adults in the wild, said Ron Tilson, who monitors the species and is conservation director at the Minnesota Zoo.

"That speaks volumes about how well zoos have done," he said.

Kira, born in a German zoo, once was considered genetically valuable in the captive North American population. Now, after four litters by four different males (the latest father is Dmitri) and 11 offspring, she may not be permitted to breed again.

Other tigers likely will be singled out to increase the genetic diversity of the captive population.

"She's done that," Waldron said. "Kira's done her job."

View a tiger cub slide show at http://go.philly.com/earth

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