Last summer Lincoln Park Zoo cautiously introduced two young and inexperienced Siberian tigers, Sheba and Sikhote, hoping that they would mate and conceive to carry on a new bloodline of the extremely endangered species.
The two quite publicly had a roaringly good romance, mating 18 times the first day they were together.
It turned out that Sheba did conceive. Last Nov. 15, late on a Saturday night, she astonished and delighted keepers by giving birth to four cubs. Most first-time tiger mothers have only one or two cubs in their first pregnancy.
One of the newborn cubs, however, a male, refused to nurse and died two days later.
Since then, Sheba and the three still unnamed cubs, two males and a female, had been isolated in a quiet, off-viewing cubbing den in the zoo’s lion house to get used to one another before putting them in a public habitat.
Tuesday morning, zoo officials decided it was time to introduce the new mother and cubs to the public, placing the romping, rollicking crew in a public indoor habitat in the lion house.
Now roly-poly 20-pound kittens, they figure to be major attractions at the zoo for the next few years. Their appeal was evident Tuesday, as they poked their noses around their new home and playfully rolled on the floor, wrestling with each other when not nursing and otherwise pestering their patient, protective mother.
Eventually, however, they will be highly sought after by other zoos as potential mating partners. That is because Sheba, their mother, born in 1992 in Brookfield Zoo, was sired by Zhivago, a Siberian male sent there from a German zoo. Species survival experts imported Zhivago to the U.S. to bring a new strain of genes into the captive North American Siberian tiger population.
There are only 250 to 400 Siberian tigers left in the wild, a population that continues to decrease. Zoos and captive breeding facilities around the world have another 700 captive animals, more than half of them in North America. Breeding specialists already are planning for the day they will try to repopulate wilderness areas with captive bred animals.
“These births will enable Lincoln Park Zoo to make a significant contribution to preserving the Siberian tiger,” Kevin Bell, the zoo’s director, said at the public introduction of the cubs Tuesday.
The care of tigers presents challenges that don’t go along with more placid animals. Initially, zookeepers had no good way to determine if Sheba was pregnant other than shooting her with an anesthetizing dart to take a blood test–something they didn’t want to do. Then tending to the cubs has required some delicate negotiations with the mother.
As a measure of how highly valued the Lincoln Park cubs are, zookeepers, who knew the fourth cub was in trouble, decided not to rescue it. They feared they would endanger the other three by separating them from their mother.
“Sheba was very, very unhappy with us when we did go in to look at the cubs for the first time when they were six weeks old,” said Robyn Barbiers, Lincoln Park’s chief veterinarian.
“We needed 15 minutes with them to give them their first cat distemper shots, so we lured Sheba to another cage where she could watch everything we were doing.
“While we were at it, we weighed them for the first time and implanted microchips in their shoulders. We didn’t want to leave a human scent on them, because tiger moms have been known to kill their cubs after such handling, so we wore surgical gloves and then rubbed them in straw and feces afterwards.”
Sheba growled through the entire 15 minutes, she said, but afterward resumed her motherly care.
The microchips are a relatively new wrinkle in zoo husbandry. About the size of a slender grain of rice, they are implanted in zoo animals as a sort of high-tech fingerprint carried by the animals for the rest of their lives. They are used to identify the animals and their genetic history when “read” by a scanning device, much like a supermarket bar code.
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Member zoos belong to a North American species survival plan for Siberian tigers that matches up animals for ideal genetic mating matches, assuring the broadest possible genetic diversity within the captive population.
Zhivago, Sheba’s father, sadly demonstrated the fragility of bloodlines in captive Siberian populations when he died about a month ago from a rapidly spreading cancer in his jaw area.
Mated at Brookfield with Adrienne, a Siberian female, Zhivago produced only three American offspring, Sheba and her sister, born in 1992; and Anastasia, a female cub born last October. Anastasia will be put on public view for the first time early next month.
At Lincoln Park, keepers are ecstatic with the three grandchildren they have from Zhivago.
“They seem extremely healthy and are doing exceptionally well developmentally,” said Alan Varsick, mammals collection manager. “We expect they’ll start weaning from their mother in another month or so.”
They will start becoming mating candidates for other zoos as they begin to approach sexual maturity around age 4, Varsik said. Until then, they will stay exclusively with Sheba. Male tigers have no part in nurturing their young.
Once they leave, Sheba and Sikhote probably will be reunited, Varsik said, though Sheba probably will be put on birth control until species survival experts decide whether they want more offspring from the pair or not.
“We hope Sheba can breed again,” he said. “She’s doing such a great job of mothering, she’s a joy to watch.”