At Philadelphia Zoo, rare tigers meet and mate
By Sandy Bauers
The Philadelphia Inquirer
Posted on Tue, Jan. 16, 2007
PHILADELPHIA - She paced in front of the mesh, flopped to her back and writhed seductively. She was the experienced one.
He hid behind a tree, staring at her, then drew closer. He was middle-aged and still a virgin.
For about an hour Tuesday morning, Kira and Dmitri, two Amur tigers, sniffed and growled as they got aquainted across the divide of two separate exhibits at the Philadelphia Zoo.
The plan - a dangerous one - was to get them to mate.
But it was worth the risk. Both carry valuable genes that can assure the viability of North America's 144 captive Amur tigers, only 400 of which remain in the wild.
The staff was nervous. Putting two tigers together can be fatal.
"Tigers are claws and teeth," said Jim Ronemus, assistant curator of carnivores. "The whole animal is a machine to make those two things work."
If their meeting turned ugly, it would be difficult for humans to separate two animals that were so large, so fast and so deadly.
Timing was everything. Unlike lions, which are social, tigers are solitary. They meet only to breed. So the zoo couldn't put them together ahead of time to see if they got along. Kira had to be in heat.
Later that day, keepers Tara Brody and Kay Buffamonte would take the two animals into an inside enclosure and allow them to interact through a single layer of mesh.
If all went well, they would raise a door and let the animals into the same space.
The staff figured Kira would know what to do. But Dmitri?
If he didn't catch on fast, he might become frustrated, then aggressive.
At 380 pounds to Kira's 250, Dmitri could kill her in under two minutes.
Not long ago, the planet was home to eight tiger subspecies.
Three have gone extinct.
Three more, including the Amur tiger, are highly endangered. The biggest of the cats has been heavily poached, both for its skin and for the Asian medicine market, and its habitat has dwindled.
In fact, it used to be called the Siberian tiger until it was renamed to reflect the one place on earth it remains - the Amur River basin along the Russia-China border.
The world's captive tigers are seen as both educational ambassadors for their wild brethren and a kind of genetic lifeboat, although no one is sure how that would work.
It is unlikely a captive tiger could survive in the wild and breed. And artificial insemination has proven unsuccessful, "despite dozens and dozens of attempts by some of the most talented reproductive biologists," said Ron Tilson, director of conservation at the Minnesota Zoo.
Every year, about 20 captive Amur tigers die. So zoos try to replace their number through breeding. Since 1981, 423 cubs have been born in zoos across North America.
Deciding whom to breed and when is a genetics math and matchmaking game taken on by a committee that monitors a "species survival plan" for the 144 tigers in North American zoos.
Dmitri once was a low priority for breeding, but then some of his close relatives died. Now, Dmitri and Kira are more distantly related from the rest of the captive tigers than most.
"So they get the magic ring," said Tilson, who coordinates the species survival plan.
If the stakes for the animals are high, so are those for the zoo.
Zoo president Vikram Dewan sees tiger cubs as an added experience for visitors and a new way to tell their conservation story. And there's no denying what cubs could do for the $25 million operating budget.
In 1994, when a pair of white lions had three cubs, they were credited with helping turn the zoo's $1.5 million deficit that year into a $125,000 surplus.
Kira and Dmitri had never met, but when she arrived in September he sensed her immediately, said Buffamonte, lead keeper for all the big cats.
"Even though the zoo has bred tigers before - 32 cubs since 1901 - each pairing is different.
Slowly, the staff began to aquaint the two animals.
Kira was let into an outdoor exhibit, where she scraped the ground, rubbed her face and urinated, leaving her scent.
Then she came in and Dmitri went out. "His head didn't come off the ground for two hours," Buffamonte said. "He was hoovering everything."
They repeated the process indoors, in the tigers' "bedrooms."
Then came visual contact. Again, the signs were good. Instead of snarling and spitting and roaring, the two tigers growled in low "chuffs," their ears perked forward.
Unlike humans, female tigers do not ovulate on their own. It is intercourse that stimulates their ovaries to release eggs.
By Tuesday morning, the tigers were separated only by two mesh walls a mere 12 feet apart.
Until this week, the zoo staff thought the pair had more time to get to know each other. But a tiger's reproductive cycle is hard to predict. After the winter solstice, the female's hormones are triggered, and she begins to go into periods of heat.
By Monday, Kira was showing clear signs of it - chuffing vigorously and rolling on the ground.
Tuesday, Brody and Buffamonte watched closely for about an hour, deciding by midmorning that it was time to introduce the tigers indoors, where they'd have more of a chance to intervene if something went wrong.
They alerted the veterinary staff, which gathered a dart gun and emergency supplies. They brought water hoses and a fire extinguisher loaded with carbon dioxide - no chemicals - to provide a distracting burst of air and a loud noise.
They pulled two levers and the animals were together.
Kira lay down and moved her tail to the side. Dmitri mounted from behind, held her neck in his jaws and thrust.
In moments, it was over.
Throughout the next hour, they bred repeatedly, said Ronemus, one of only three people allowed to watch, for fear of agitating the animals and inciting aggression.
But then, Kira began to roar and slapped at Dmitri, backing him into a corner. The staff yelled to distract her.
Finally, after seven attempts at mating, four of them successful, the two tigers lay in separate areas, panting, exhausted.
The keepers shut the doors between them.
If Kira becomes pregnant, they'll soon notice a weight gain.
There could be cubs by May.