Dr. Monfort wants zoos to raise more money for the conservation of animals in the wild and to make that effort as important as erecting fancier accommodations for their captive collections. Zoos, he said, should build facilities — not necessarily open to the public — that are large enough to handle whole herds of animals so that more natural reproductive behavior can occur. And less emphasis should be placed on animals that are popular attractions but are doing fine in the wild, like African elephants and California sea lions, Dr. Monfort said, adding that they should be replaced with animals in desperate need of rescuing.

Many zoo directors say that such a radical reordering is not called for and that each zoo does valuable work even if conserving just a few species.

But Dr. Monfort is not satisfied. He wants all zoos within the Association of Zoos & Aquariums to aim higher on conservation efforts. “I am comfortable with raising the standards for zoos so that eventually it will be harder and harder to be accredited unless you are doing that,” he said in an interview. “If you can’t keep up, then you probably need to be dropped off the bottom.”

Established in 1910 and built on 90 acres, the St. Louis Zoo is in many ways archetypal of institutions struggling to adapt from a late-19th-century concept to a 21st-century crisis management center.

In their first century, American zoos plucked exotic animals from the wild and exploited them mainly for entertainment value, throwing in some wildlife education and a touch of preservation. When wilderness began disappearing, causing animals to fail at an accelerating pace, zoo officials became rescuers and protectors. Since the 1980s, zoos have developed coordinated breeding programs that have brought dozens of animals, like the golden lion tamarin of Brazil, back from the brink.