ST. LOUIS (The New York Times) -- With fluorescent yellow eyes and tufts of hair sticking straight up behind their ears, Bonner and Etienne look like slightly crazed old men. 

 

Zoos are on the verge of giving up on lion-tailed macaques, which once flourished in the tops of rain forests in India. 

 

These riotous and chatty lemurs — known for elaborate rituals that include grooming and braying — once ranged across eastern Madagascar. 

 

Now scores of these black-and-white ruffed lemurs are being bred here at the St. Louis Zoo and at other zoos across the United States as part of a broader effort to prevent their extinction. 

 

But Ozzie, a lion-tailed macaque, will never father children. Lion-tails once flourished in the tops of rain forests in India, using their naturally dark coloring to disappear into the height of the jungle. 

 

Though there are only about 4,000 remaining in the wild, not one among Ozzie’s group here in St. Louis will be bred. American zoos are on the verge of giving up on trying to save them. 

 

As the number of species at risk of extinction soars, zoos are increasingly being called upon to rescue and sustain animals, and not just for marquee breeds like pandas and rhinos but also for all manner of mammals, frogs, birds and insects whose populations are suddenly crashing. 

 

To  conserve animals effectively

 

To conserve animals effectively, however, zoo officials have concluded that they must winnow species in their care and devote more resources to a chosen few. 

 

The result is that zookeepers, usually animal lovers to the core, are increasingly being pressed into making cold calculations about which animals are the most crucial to save. Some days, the burden feels less like Noah building an ark and more like Schindler making a list. 

 

The lemurs at this zoo are being saved in part because of a well-financed program to rescue rare fauna of the island nation of Madagascar. By contrast, although St. Louis has kept lion-tailed macaques since 1958, other zoos started getting rid of them in the 1990s because they can carry a form of herpes deadly to people. 

 

With only an aging population left in captivity in the United States, a species advisory group to North American zoos is expected to put the animals on a phaseout list soon. 

 

If there are criticisms, they are that zoos are not transforming their mission quickly enough from entertainment to conservation. 

 

“We as a society have to decide if it is going to be ethically and morally appropriate to simply display animals for entertainment purposes,” said Dr. Steven L. Monfort, the director of the Smithsonian Conservation Biology Institute, part of the National Zoo in Washington. “In my opinion, that model is broken. There needs to be an explicit role for zoos to champion species.” 

 

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.