Portland's zoo has had a long and troubled history with polar bears, going back more than a century.

Zero and Zerex died tragically within months of each other in the early 1960s. Esco-Mo and Ice-Ter had difficulty reproducing in the 1970s and early '80s, and died of complications from food poisoning.

Siblings Conrad and Tasul lived at the zoo from the mid-1980s and were crowd favorites. But even though they lived long past their life expectancy, they were euthanized within months of each other last year.

And then there's the cub Nora, who was relocated to a zoo in Salt Lake City in September and faces an uncertain future.

Over the years, about two dozen polar bears have lived or been born at Portland's zoo (though six were cubs who were stillborn, or died within a few days of their birth). Some of these bears stayed at the zoo for a few years before moving to other zoos. Others would call Oregon home for a long time.

The stories of these bears are sometimes tinged with sadness, with a few tragic endings. But they illustrate just how much zoos and animal care have changed, from places of pure spectacle at the expense of the animals, to places where research could play a crucial role in the survival of the species.

***

If you know where to look, you can find the exact spot in Washington Park where the Oregon Zoo's polar bear story began in 1905.

It's a secluded grove of rhododendrons and ferns, just steps from the Coming of the White Man statue and an easy walk from the Oregon Holocaust Memorial that draws thousands of visitors every year. Perched near the crest of a steep hillside above West Burnside Street, it's a quiet place except for the dull roar of city traffic and the occasional birdsong.

A 1908 souvenir postcard shows the polar bear exhibit at City Park Zoo (now the Oregon Zoo) in Washington Park. The iron-barred and cement block structure was home to the polar bear Polar from 1905 to 1915. (City of Portland, OR, Archives, A2004-002.3645)

Across a dirt footpath sit the ruins of a stone wall. From this viewing area for a decade, Portlanders watched a polar bear pace back and forth inside a pen that was about as big as a typical family room. The pen was made of cement blocks and iron bars, and included a small wading pool that was 5 feet deep. A fence of chicken wire and two-by-fours was the only thing keeping spectators from getting too close.

The bear, named "Polar," came to what was called City Park Zoo after being part of the Lewis and Clark Centennial Exposition. The bear was fed a daily diet of a gallon of milk and 5 pounds of cod liver oil, and exhibited repetitive behavior that convinced zoo visitors he was suffering. Polar bears in the wild are carnivores that mostly feed on fat-rich seals.

At the time, The Oregonian speculated on the bear's disposition: "In his iron-barred cage, he stood peering into the open fields beyond. Swinging his head to and fro, to and fro unceasingly, it seemed he was longing for liberty."

In 1909, after hearing complaints, Portland Mayor Harry Lane visited City Park Zoo. He was so disturbed by what he saw of the polar bear enclosure and by the way the other animals were treated that he called for the zoo to be abolished.

"I am of the opinion that there is nothing more cruel in the world than holding wild animals in captivity as is being done at the City Park," Lane told The Oregonian. "It is the most cruel, inhumane thing I ever saw. It makes me sick to think of it. It is shameful."

"Polar," the polar bear that was displayed at the City Park Zoo (now the Oregon Zoo) in Washington Park from 1905 to 1915, as seen in an undated photo. (Oregon Historical Society, #bb016219)

The mayor's outrage set off a city-wide debate, with most of the attention focused on the tight confines of the zoo's polar bear. The head of the Oregon Humane Society called for the polar bear to be euthanized with chloroform to end its suffering. People wrote letters to the editor begging for the bear to be moved to a more hospitable place.

Lane is primarily remembered as the person who inspired Portland's Rose Festival. He also supported women's suffrage and appointed one of the first female police officers in the country. He spoke out against racism, especially violence against Native Americans. And he hated Portland's zoo, vowing that he would never approve funding for the purchase of any more animals from climates significantly different from Oregon's.

It proved a hollow promise. Lane got pushback from city commissioners and the board of the city's park system. He was in the final year of his second two-year term as mayor, and his political ambitions extended beyond Portland. In 1912, he was elected to the United States Senate, where he continued fighting for suffrage and better relations with Native Americans, but he appeared to lose interest in the plight of Portland's zoo animals.

City Park Zoo would go on, and Polar remained there until he died in 1915 from an undiagnosed illness. His pelt was mounted and displayed at City Hall, a final indignity for a polar bear that had endured so much.

The original exhibits at City Park Zoo were either torn down or abandoned, and most of the zoo grounds now are a grassy field where people sunbathe, throw Frisbees, and play fetch with off-leash dogs.

***

In 1943, another polar bear arrived at Portland's zoo almost by accident.

Mishka was a 50-pound cub acquired by the captain of a Soviet freighter in the Arctic and was kept on board as a pet. When the ship docked in Portland, word of the bear got to zoo director Arthur Greenhall, who talked the captain into giving the polar bear to the zoo. When the bear was taken from the ship, its fur was matted with grease and oil from playing with the ship's gears and winches.

The old polar bear pen that Polar had used decades earlier had been replaced by a main cage building, which housed a menagerie of cougars, lions, snakes and monkeys. Over the years, it would prove an unsuitable environment for Mishka, who would grow to 800 pounds, and once bit the index finger of a visitor who tried to feed it a candy bar, causing minor lacerations.

Then in 1948, Mishka escaped from his cage. It was near closing time on a Saturday night when visitors discovered the polar bear outside the zoo's cage building. The bear chased a zookeeper into a basement, charged a car that was trying to herd it back into the building, and forced new zoo director Jack Marks to climb a ladder and seek safety atop a 12-foot-high cage.

A news clipping from The Oregonian from Jan. 4, 1948, chronicling the escape of the polar bear Mishka.

Firemen tried to use chemical fire extinguishers and water hoses to force Mishka back into his cage, without success. Eventually, he was lured back with a bit of horse meat. Zookeepers slammed the cage's door shut and replaced the padlock the bear had broken off.

In 1955, Mishka was sold to the Dallas Zoo in exchange for a half-dozen prairie dogs, a black leopard and a ring-tailed cat. He was later transferred to the Fort Worth Zoo, where he died in 1966.

***

In 1959, the zoo, now called the Portland Zoological Gardens, moved to its current location off U.S. 26. It opened with a significantly improved polar bear exhibit.

The polar bear grotto, a large open-air area, featured concrete platforms and pools for sunbathing and swimming, along with dens where the bears could escape the public eye. The grotto was surrounded by a deep moat and high walls, from which visitors could observe the bears.

Zero and Zerex were about 3 years old when the new zoo opened. They each weighed about 500 pounds. The bears were born in the wild, where they had been captured by Eskimos near Kotzebue, Alaska, and raised by the tribe's children. They arrived in Portland a couple of years before the zoo moved.

Dr. Mathew Maberry attempted to rope a polar bear on Aug. 28, 1959, so workmen could get into cage to fix steel doors. Paul Pratt, zoo attendant, stood by with a rifle for protection. (Carl Vermilya, The Oregonian)

Zero and Zerex were playful, and their strength took a toll on the grotto. Within a couple of months, they had torn four 100-pound steel sliding doors off their tracks, making it impossible for zookeepers to safely clean the exhibit.

To make repairs, zoo veterinarian Mathew Maberry sedated the bears with a cocktail of tranquilizers and sleeping tablets tucked into morsels of fish. Before the bears finally dozed off, Maberry said they each had taken enough tranquilizers to knock out 10 male buffalo, and enough sleeping pills to give 75 people a good night's sleep.

While workmen secured the doors with larger bolts, a zoo attendant stood by with a loaded rifle — just in case.

The bears remained among the zoo's top attractions until 1966, when they died in separate tragedies. Zero swallowed a rubber ball thrown into the pen by a visitor. A postmortem revealed that the ball had lodged in his stomach, blocking his intestines.

Zerex died a few months later when she was shot after mauling a temporary zoo employee who had fallen into the bear's grotto while trimming shrubbery. The man suffered serious bites to his legs, hips and arms while he was dragged around for 15 harrowing minutes. Zookeepers first tried to get the bear to back off using a firehose. When that didn't work, she was shot.

Because the bears were so popular, a public campaign to replace them began almost immediately.

***

Portland's polar bear fans didn't have to wait long for new residents. In July 1967, 6-month-old cubs Esco-Mo and Ice-Ter arrived. The bears were gifts from the employees of ESCO Corp. and Hyster Co., the basis for the bears' unusual names. They were purchased by a Dutch animal dealer for $2,200 — about the price of an economy car at the time.

Both cubs had been wild-born in Russia but had been abandoned by their mothers. Because they were unrelated, zookeepers hoped that one day they would become a breeding pair.

Over the years, the zoo had limited success on that front. In 1973, Ice-Ter gave birth to a pair of cubs, but one was stillborn and the second died a week later from pneumonia. The following year, she gave birth to another pair, and all appeared well, as the mother and cubs stayed in seclusion in the grotto's maternity den, with zookeepers monitoring the sounds of the newborns through a speaker system. After about a month, zookeepers stopped hearing the cubs, and entered the den a week later to discover that Ice-Ter had eaten them, as sometimes happens in the wild. It's not known if the cubs were dead before they were eaten.

Ice-ter and her cub Cheechako at Washington Park Zoo on April 19, 1977. (Wes Guderian, The Oregonian)

In 1976, Ice-Ter gave birth to a male cub, who would be named Cheechako (Chinook jargon for "tenderfoot"). After a few months, Cheechako emerged to swim and play in the sunshine. There's always excitement about new babies at the zoo, but there was particular interest in Cheechako, since he was the first of the zoo's cub cubs to survive.

Cheechako stayed at the zoo until 1978, when he was sold to Utah's Hogle Zoo in Salt Lake City (the zoo that would eventually become Nora's home). During his time in Oregon, he grew from one pound at birth to more than 300 pounds. But the mother and cub had to be kept separated from Esco-Mo, and selling the cub would allow the two adult bears to be reunited for further mating.

Ice-Ter had two more cubs in 1978 and a single cub in 1981. They would eventually move to zoos in Sacramento, California, and Seoul, South Korea.

The zoo lost both Esco-Mo and Ice-Ter in 1982, when the 16-year-old bears died from fish parasite poisoning after eating tainted salmon. The bad fish made 13 other bears at the zoo sick, though they all recovered. Ice-Ter was pregnant at the time of her death, compounding the tragedy.

***

The polar bears that many Oregon Zoo visitors remember most are Conrad and Tasul, siblings who arrived in Portland in 1986 as 15-month-old cubs from a zoo in Columbia, South Carolina. The zoo unveiled a new $2.6 million polar bear exhibit, which included summer and winter settings, along with an underwater viewing area where people could see them swim.

Conrad and Tasul were joined by other bears (most notably Yugyan, a female who arrived at about the same time, and lived until 2008, and Shivers, a male who stayed at the zoo until being transferred to a Mexican zoo in 1998), but because they lived at the zoo so long, zookeepers learned a lot from them about bear physiology, particularly as they needed treatment for arthritis and other age-related ailments.

And there were a number of scientific breakthroughs.

In 2011, Tasul became the first polar bear in captivity to have blood drawn without being anesthetized. Conrad would do the same the following year.

Polar bears Conrad (left) and Tasul try out their new toy, a bowling ball, on March 27, 1986. (Dale Swanson, The Oregonian)

Tasul also became the first captive polar bear to wear a collar that tracked her movements, which helped biologists learn more about how to track polar bears in the wild, part of crucial research as climate change threatens the species.

The median life expectancy for polar bears is 20.7 years for males and 24.1 years for females, according to the Oregon Zoo. When Conrad was euthanized last year at age 31, he was the oldest male bear in North America. And when Tasul was euthanized a few months later, she was the third-oldest bear in any North American zoo or aquarium.

With Conrad and Tasul gone, and Nora now in Salt Lake City, the Oregon Zoo is about to embark on its next chapter with polar bears. Construction will soon begin on a new exhibit, Polar Passage, scheduled to open in 2020. It will give polar bears more space and a tundra-like setting in which they can roam as they would in the wild.

It's a long way from the iron-barred polar bear cage of Portland's original zoo that firebrand Mayor Harry Lane hated so much.

Polar bears at the zoo

These are the bears that have called the Oregon Zoo and its predecessors home. The dates indicated the years the bears were at the zoo.

Polar

– 1905-1915

Mishka

– 1943-1955

Zero

– 1956-1966

Zerex

– 1956-1966

Esco-Mo

– 1967-1982

Ice-Ter

– 1967-1982

Tundra

– 1970-1976 (male, wild orphan from Baffin Bay, sold to a dealer for shipment to a South Korean zoo)

Crystal

– 1970-1976 (female, wild orphan from Baffin Bay, sold to a dealer for shipment to a South Korean zoo)

Huff-n-Puff

– 1972-1978 (female, from Seattle’s Woodland Park Zoo, transferred back to Seattle)

Unnamed

– 1973 (Ice-Ter’s cub, gender unknown, stillborn)

Unnamed

– 1973 (Ice-Ter’s male cub, died of pneumonia after 1 week)

Unnamed

– 1974 (Ice-Ter’s cub, gender unknown, died in den after about 1 month)

Unnamed

– 1974 (Ice-Ter’s cub, gender unknown, died in den after about 1 month)

Cheechako

– 1976-1978 (Ice-Ter’s male cub, transferred to Hogle Zoo in Salt Lake City)

Adak

– 1978-1979 (Ice-Ter’s male cub, transferred to the Sacramento Zoo)

Mukluk

– 1978-1979 (Ice-Ter’s female cub, transferred to the Sacramento Zoo)

Unnamed

– 1981-1982 (Ice-Ter’s male cub, sold to a dealer for shipment to a South Korean zoo)

Conrad

– 1986-2016

Tasul

– 1986-2016

Kdax

– 1986 (female cub, from Cleveland, died from intestinal infection after a month at zoo)

Yugyan

– 1986-2008 (female, from Cleveland, died from kidney failure)

Shivers

– 1986-1998 (male, from Columbus, transferred to Leon, Mexico)

Unnamed

– 1991 (Tasul’s cub, gender unknown, died after 2 days)

Unnamed

– 1991 (Yugyan’s cub, gender unknown, died after 4 days)

Nora

– 2016-2017

-- Grant Butler

503-221-8566; @grantbutler