The zoo carefully planned her courtship with its new male, Zenda. Keepers took Isis off birth control. The community was excited.
But nothing happened.
And it wasn't just at Brookfield. The lioness Asali, at
At the same time, scientists at the
The implants, meant to last six months to a year, were still working three, four even five years later.
Now researchers here and across the country are trying to figure out the extent of the problem, the impact on zoo breeding programs -- and whether some of these animals will ever bear offspring again.
The Wildlife Contraception Center, an arm of the
But it has documented only 88 animals that have "reversed" -- gotten pregnant or produced sperm -- in nearly a decade of treatments.
Of the 200-plus species treated, the center has seen reversals in just 50. Not one of the six or seven polar bears given Suprelorin, species experts said, has had cubs.
It is far too early to draw conclusions, researchers say. Many of the zoos caring for those animals have not yet tried to breed them. Still, the zoo community is unsettled.
"I think we all should be worried," said Budhan Pukazhenthi, a reproductive physiologist at the
The issue is key to the future of North American zoos. Still transitioning from the years of cages and pits, zoos now often say they exist for two primary reasons: to educate the public on wildlife conservation, and to provide a backup plan should species die out.
To accomplish the first goal, leaders prefer to exhibit animals in wild settings -- herds of elephants, bands of gorillas, prides of lions. But to achieve the second, and for the ongoing health of their animals, they need to carefully watch those family groups, and allow breeding only between individuals of the right genetics, at the right time.
The alternative, zoo leaders note, is to kill unwanted animals, as do some European zoos. Last week, the
At last fall's
To fix the problem, they explained, they first need to understand how serious it is.
Lions were the poster children at the meeting. Keepers had already begun sharing data with the
And they had some numbers: 118 lionesses had been treated with Suprelorin, said
Only nine had documented reversals.
TEETH, CLAWS AND BLOOD
Like most U.S. zoos, Brookfield has long had lions. They are popular animals and draw crowds.
They also weren't really a priority 30 years ago, said
Then they started dying in the wild by the thousands. Some were killed by diseases such as canine distemper, a virus that ravaged jackals, foxes and dogs. But far more died by spear, trap and poison as their territory collided with human expansion, and African farmers and herders protected their land and livestock, according to
Suddenly zoos were more interested in telling the story of lions, Zeigler said.
Brookfield, however, didn't have a female. And the zoo couldn't decide on its own to find and breed lions. Zoo leaders, through the
Finally, in 2008, the association's lion team sent the zoo Isis, age 2, from the
Sex between wild animals isn't a sterile event. "Lion mating involves teeth and claws and a little bit of blood," said
Baby animals are nearly always a big deal, said
But lion cubs are especially endearing, he said. They wrestle each other. They jump on their mothers.
Moreover, they're a big part of the conservation experience, he said. Female lions in a wild pride are the hunters. When they leave to hunt, one stays behind to care for the cubs. "That's the kindergarten," Peachey said, borrowing a term from field biologists. "We want to exhibit that social setting.
"Breeding is a big part of our mission," he said. "And super fun for staff."
The zoo association, however, didn't immediately give Brookfield the green light to breed.
Lions are assigned a number that designates their genetic worth. Isis and Zenda weren't the most genetically valuable at that moment, so the association team didn't move them to the front of the line. Besides, Isis was still a little young.
So, in 2009, Brookfield put Isis on one dose of Suprelorin.
'BAD SIDE EFFECTS'
Suprelorin was a godsend at first. From 1975 until the early 2000s, keepers used the drug Melengestrol acetate, or MGA. But as the years of treatment mounted, zoos were discovering lionesses with diseased reproductive tracts. Sometimes the cats died.
In 2002, a group of scientists published a paper after studying preserved tissue from more than 200 wild cats. MGA, they found, was tied to uterine overgrowth, lesions, sterility and, sometimes, cancer.
At that point, zoos basically stopped using MGA.
And for a few years, leaders didn't know what to do. Most simply didn't implant their lions with any contraceptives.
But Asa helped swing a deal with the
But the zoo community embraced it. Early studies -- some by PepTech itself -- indicated Suprelorin was safe, effective and promised to be reversible. For several years, all went well.
"We were focused on health," Asa said. "And it hadn't occurred to me that it wouldn't be reversible."
Keepers were perhaps the first to realize something was wrong.
In 2009, Zoo Atlanta had seven lions: four adults and three new cubs. "We had a lot of lions to manage," said
A year later, however,
In 2012, the zoo association's Population Management Center analyzed the status of zoo lions. In general, the study found, things were fine. Still, it warned, "if the females on contraceptive do not breed again, the population will experience a much more severe decline..."
No matter how this ends, some zoo staffers say they'll be more cautious going forward.
"I think it was sort of recommended across the board without really knowing what the long-term consequences were going to be," said Zoo Atlanta's Snyder. "I think we all learned a lesson from that."
The call for data from other zoos, Asa hopes, will help flesh out the issues. Still, Asa and her team have already learned some things. The implant breaks up under the animal's skin. If veterinarians can remove it first, animals reverse more quickly.
And some animals, for no particular reason, seem to be recovering on their own. Neka, in
Others are still waiting.
It's now been three or four years since the
And Brookfield's still hopeful. Isis showed signs of going into heat last fall, Zeigler said. Zenda seemed interested. But, still, no success.
"This is why we brought this pair in," Zeigler said.
"And it's sort of been a waiting game ever since."
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