William Conway, Who Reimagined America’s Zoos, Is Dead at 91

William G. Conway, an animal conservationist who redefined (but failed to rename) the Bronx Zoo, and who helped recast America’s urban wildlife parks into crowd-pleasing natural habitats designed to generate support for endangered species worldwide, died on Oct. 21 in New Rochelle, N.Y. He was 91.

His death, in a hospital, was announced by the Wildlife Conservation Society, where he had spent virtually his entire career. He joined the society in 1956 as an assistant bird curator and retired in 1999 as president and general director.

Dr. Conway single-mindedly transformed the society’s signature attraction in the Bronx from a famous but fusty cloister for neurotic caged specimens into a collection of lush natural environments where the animals presumably felt more at home, and where visitors benefited from a more authentic educational experience.

On his watch, the Bronx Zoo opened the Children’s Zoo and exhibits including World of Birds, JungleWorld, the Baboon Reserve and the 6.5-acre Congo Gorilla Forest.

“Today the Bronx Zoo/Wildlife Conservation Park contains more examples of progressive zoo exhibit design than any other, almost all of them based on concepts by William Conway,” David Hancocks, an architect and designer of zoos and nature centers, wrote in “A Different Nature: The Paradoxical World of Zoos and Their Uncertain Future” (2002).

Dr. Conway’s tweedy attire, and his use of Britishisms like “cheerio,” suggested that he hailed from the Midlands rather than the Midwest (he was born in St. Louis).

But New York officials discovered that there was a flinty negotiator behind that facade in the 1980s, when the conservation society assumed responsibility from the city government for managing and renovating the impoverished municipal zoos in Central Park, Prospect Park in Brooklyn and Flushing Meadows Corona Park in Queens, as well as the New York Aquarium in Coney Island.

By the time Dr. Conway retired after 43 years, the society was involved in more than 300 conservation projects in 52 countries. In the preceding decade, attendance at the city’s zoos and aquarium had grown to 4.4 million from 3.1 million; the society’s budget had more than doubled, to $78 million; membership had tripled, to nearly 95,000; and private fund-raising had doubled, to $21 million.

Dr. Conway tactfully named animals after rich benefactors: Astor the elephant for the society matron Brooke Astor; 11 giraffes for James Walter Carter, a coal mogul. Asked in 1999 whether only oligarchs get naming rights, he told The New York Times, “I confess there are a pair of gibbons at JungleWorld named for my wife and myself.”

Dr. Conway “redefined what zoos and aquariums should be and how they should operate,” Jim Breheny, the director of the Bronx Zoo, said in a statement after Dr. Conway’s death, adding that at the society, and as president of the American Zoological Association, Dr. Conway focused on “care, ethics, integrity and conservation,” including swapping animals between zoos to improve the likelihood for breeding and genetic diversity.

One metric that has not increased at New York’s zoos is the number of elephants, now down to two in the Bronx. (When one gave birth in 1981 to a 180-pound bull calf, Dr. Conway proudly declared, “It’s the first elephant born in the New York area in about 9,500 years, although I guess that was a mammoth.”)

In 2006, after several elephants at the zoo had died of disease or injuries, Mr. Breheny announced that no more would be acquired. (Dr. Conway said flamingoes and penguins were his favorite animals, anyway.) Instead, the society would devote its resources to conserving them in the wild.

“The justification for removing an animal from the wild for exhibition,” Dr. Conway said in an early report, “must be judged by the value of that exhibition in terms of human education and appreciation, and the suitability and effectiveness of the exhibition in terms of each wild creature’s contentment and continued welfare.”

In recent years, the Nonhuman Rights Project, an animal-rights organization, has been pursuing a habeas corpus case to liberate one of the two elephants still in the Bronx, a female named Happy, on the grounds that she isn’t.

While Dr. Conway was acclaimed by his colleagues as a conservationist, he exasperated the public when he stepped into another field: semantics.

In 1993, he replaced the word “zoo” (too evocative of confusion and disorder, he said) and rebranded the renowned institution in the Bronx as the International Wildlife Conservation Park (it was formally the New York Zoological Park).

The name change prompted Daniel Berger to write in The Baltimore Sun, “Endangered species cry out for preservation, as does the language.” In his On Language column in The New York Times Magazine, William Safire responded more succinctly by delivering a proverbial “Bronx cheer.”

Eventually, demonstrating that language and reasoning distinguish humans from other animals, officials retained the name “Bronx Zoo” atop a smaller sign that read, “Bronx Wildlife Conservation Park.”

“One in 10 voters in the United States lives within 50 miles of this zoo, and most will never see any wildlife but starlings, pigeons, roaches and rats,” Dr. Conway told The Times in 1972. “We want to convince city people that wildlife is worth preserving.”

Dr. Conway was not celebrated for his sense of humor, but neither was he routinely unsmiling. In 1968, he wrote a paper titled “How to Exhibit a Bullfrog: A Bed-Time Story for Zoo Men.” He once described architects as the most dangerous animals in captivity.

In 1962, he gamely appeared on the CBS-TV show “To Tell the Truth,” alongside two impostors also claiming to be the youngest director of any zoo in the United States. The actress and journalist Betty Furness was the sole panelist who guessed that he was the real William Conway.

In 1982, he published a plaintive letter, supposedly written by a chimpanzee, that concluded: “I have been made aware of the fact that not all human beings are insensitive to the need to find substitutes for monkeys and apes as experimental animals. A colleague called to my attention a recent address by the dean of a prominent Eastern medical school which states in part, ‘Those who would enter the field of medical science should prepare themselves for self -sacrifice.’”

William Gaylord Conway was born on Nov. 20, 1929, in St. Louis to Frederick and Alice (Gaylord) Conway. His father was an artist.

When Bill was 4, he began assembling a personal menagerie by collecting butterflies, which he presented to his elementary school upon graduating. As a teenager he volunteered at the St. Louis Zoo.

After earning a degree in zoology from Washington University in St. Louis in 1951, he worked at the St. Louis Zoo and helped establish the Cheyenne Mountain Zoo in Colorado Springs before moving to the grounds of the Bronx Zoo with his wife, Christa Berthoud, a wildlife photographer. They lived there for a time with a parrot named Jimmy, who, Dr. Conway said, possessed “an absolutely marvelous disreputable vocabulary.” They later moved to New Rochelle.

His wife is his only immediate survivor.

In 1961, when Mr. Conway was 32, he was named director of the Bronx Zoo. Five years later, he became general director of the New York Zoological Society, as the Wildlife Conservation Society was known at the time. He was appointed the society’s president in 1992.

In 1999, he said he was leaving because he had told the society’s chairman that 70 seemed like a proper retirement age. “I made a terrible mistake,” he told The Times. “I should have said 95.”

Alex Traub contributed reporting.