LINCOLN PARK — Lincoln Park Zoo's new polar bears Kobe and Siku are sleeping together — and that's no euphemism.
"Everything is progressing really, really well," Dave Bernier, the zoo's general curator, said Friday, two days after the bears were introduced.
Bringing a pair of apex predators together can be dicey, but the zoo's newly renovated Arctic Tundra exhibit was designed to accommodate the entire process in the Polar Bear Species Survival Plan, beginning with keeping the bears apart and slowly getting them used to each other.
"We call them 'howdies,'" Bernier said, increasingly close encounters across various dividers leading up to a meeting four days before their formal introduction in which they had nothing but a wire mesh screen between them.
"They wanted to be together," Bernier said. "They were ready for the introduction."
Even so, when that face-to-face meeting finally came Wednesday, the 565-pound, 17-year-old female Kobe immediately "established that she was in charge," Bernier said, over the 1,000-pound, 7-year-old Siku, who was actually the first to take up residence in the Arctic Tundra exhibit in the fall, followed by Kobe a month ago.
That was the behavior zookeepers wanted to see.
"She is a very confident bear and made sure she was laying down the rules about how they were going to interact with each other," Bernier said. "He figured it out very quickly."
At first, he added, Kobe didn't want Siku in the same enclosure when she was resting. He got the message and bunked down in the next enclosure. But as of midday Friday, Bernier said, "They're both napping just now in the same enclosure."
Can the pitter patter of little polar bear cub paws be far behind?
According to Bernier, they got a late start on the breeding season with Kobe's arrival in March. "We're about midseason right now," he said.
But that still leaves plenty of time for the bears to consummate things this year. Zookeepers will be testing Kobe's fecal matter for hormone levels, Bernier said, "but we probably won't be able to tell if there's any change in her reproductive hormones until some time in the later summer."
At that point, they might again be separated for "cubbing season," which could lead to a birth sometime between late November and early January.
"They're pretty much helpless when they're born," Bernier said. It would be months of nursing until the cubs' eyes open and they became mobile, and they'd remain with the mother through the breeding season of the following year, up to two years before they'd have to be farmed out to other zoos, although female cubs can remain with the mother somewhat longer.
Bernier said there was no theory behind picking an older female to breed with a younger male. It could have gone the other way. But they were selected for genetic compatibility and "to maximize the genetic strengths of the population" by the national Polar Bear Species Survival Plan, which even keeps a "stud book" on the breeding bears available.
"The goal is to move animals around, mate new pairs, because maybe there's an issue with that pair," Bernier said. Kobe, for instance, was bred with a bear in the Pittsburgh Zoo, but it produced no offspring. This, meanwhile, is Siku's first time being put out to stud, after he arrived from the Louisville Zoo in the fall.
Bernier said there's no competition between Lincoln Park and the Brookfield Zoo to see who can produce polar bear cubs first, even though Brookfield too welcomed a new female this winter with the intent to breed.
"We're all working toward the same goal," he added. "We're trying to make the population stronger."
He did grant, however, that cubs could create a potential marketing bonanza for the zoos — not to minimize the impact of just having a pair of adult polar bears together.
"Polar bears have kind of a special place in people's hearts," Bernier said. "This is a great time to come out and see them. We'll have two polar bears roaming around the entire exhibit at least until late summer. We may separate the male out once we get into the denning season if she is pregnant.
"You'll be able to see them both together," he added, "having quality time outside."