No matter how hard the Minnesota Zoo's Ron Tilson plotted and toiled to halt the rapid decline of the world's wild tiger population, the majestic beast's numbers continued to plummet.

Futility aside, Minnesota Zoo Director Lee Ehmke is convinced that the wild tiger population "would be in worse shape if not for the work of Ron and the other tiger experts."

Tilson, the zoo's director of conservation until his retirement in 2011 and a world leader in preserving tigers, died unexpectedly Saturday in his sleep at his Apple Valley home. His family said he had been battling kidney cancer of late and was feeling ill in recent days. Tilson was 69.

Tilson joined the Minnesota Zoo staff in 1984, holding leadership positions in research, biological programs and conservation.

"His reputation within the zoo and the large cat conservation community was enormous," Ehmke said.

Among his most significant achievements include creating the zoo's "Adopt-A-Park" program in Indonesia, initiating the Sumatran Tiger Conservation Program, and coordinating the Association of Zoos and Aquariums' Tiger Species Survival Plan.

He spent years under field conditions in Asia, primarily Indonesia, as well as Africa and Central America, giving hundreds of lectures, writing or contributing to more than 220 scientific and general-audience books and articles.

"The overall news is not good" for the fate of tigers in the wild, Ehmke said, noting there were about 100,000 in the first part of the 20th century but now "about 4,000 left in the wild."

What tigers remain, other than in captivity, "live in Asia, and a lot of people live in Asia," said Ehmke, whose zoo has had up to 25 tigers and now houses five.

In a 2009 interview with the Star Tribune, Tilson explained what's to blame for the species' rapid decline, saying, "The only three things that can kill a tiger are loss of habitat, loss of prey and poaching."

Tilson, who grew up in Billings, Mont., and earned undergraduate and graduate degrees from the University of California-Davis, began his wildlife preservation work a decade before joining the Minnesota Zoo. In 1974, he helped create the Teitei Batti Wildlife Reserve in Indonesia.

His other global efforts included advising the Chinese government in 2000 to develop wilderness-based recovery options for South China tigers and creating the Tiger Information Center, a website that has had millions of visitors from 120 countries.

Tilson also was relied upon for expert court testimony in the prosecution of animal traffickers. He also put his name behind legislation seeking the responsible care of large, dangerous animals in the private sector.

"There are probably more private tigers in the state of Texas than in all of Asia," Ehmke said. "That was one of [Tilson's] interests, looking at people who want to have a tiger in his back yard and wanting to do something about it."

Tilson's son, Lincoln, said there wasn't anything particularly special about having a world expert on tigers as a father, but he did think it was kind of neat to be able to go behind the scenes at the zoo on occasion and "have birthday parties and be able to … feed the animals back in the day, when I was much younger."

Tilson, who served as a Marine Corps reserve and in the Peace Corps in Malaysia, is survived by his wife, Janet, and son Lincoln. A gathering of family and friends will be held from 3 to 6 p.m. Thursday at Henry W. Anderson Mortuary, 14850 Garrett Av., Apple Valley.

Paul Walsh • 612-673-4482