In the past, zoo acquisitions often involved collecting animals from the wild.

Historically, that's how zoos started: bringing exotic animals from far-away lands so locals could be amazed. Zoos still are popular locations for visitors to be amazed by the beauty and variety of wildlife, but they also have evolved into institutions of education and conservation.

When zoos need replacement animals, for many species it no longer is possible or advisable to look to the wild as a source. That's not to say that it doesn't still happen, but when it does, it often is to rescue animals in dire straits, such as animals about to be culled (African elephants, Tammar wallabies), ones that are endangered by an introduced species (Marianas fruit doves, Guam rails) or the last of a species that won't survive without intense intervention (California condors, black-footed ferrets).

As conservation organizations, zoos have acknowledged this change and are striving toward self-sustaining captive populations.

If zoos want to continue to have diverse collections, they need to be able to work with the populations they have in a manner that will provide zoos with animals for the future. If we can successfully breed what we need or wish to display, there no longer would be a need to consider taking animals from the wild. If the situation presents itself, we may even be able to send some back to the wild.

Managing multiple sustainable populations isn't something one zoo can do on its own.

To have a long-term, healthy and productive population, there has to be numbers large enough to keep the population genetically and demographically healthy.

One zoo simply can't hold that many of one species, let alone a varied collection of them. Plus, it would be like putting all your eggs in one basket where a hurricane or other disaster could wipe out the entire population in moments.

With a focus on sustainability, each zoo must consider which species they can manage well and what role they will play (breeding facility, holding facility).

These decisions are based on facility, habitat, expertise and budget. If you don't have the capability to offer 100 pounds of bamboo to a giant panda each day, then you don't have giant pandas in your collection. Red pandas eat a much smaller amount of bamboo and need supporters also. If you can't keep polar bears cool enough, you consider a more temperate or even tropical species.

Does your facility offer the perfect environment for breeding guira cuckoos (which would include having room to hold offspring if they can't be placed elsewhere), and does the staff know how to encourage and assist with such endeavors? Or would your efforts be more effective as a holding facility for offspring that won't be needed as breeders for awhile?

The animals involved don't have to be endangered for the work to be valuable. Many practices learned and perfected by working with common species can help with rarer ones.

Sustainability is a multi-faceted issue that may sound foreign to you, except as it applies to your local zoo.

However, if you think about it, if we focused on sustainability in the wild a long time ago, some of our endangered or threatened species may not be in the situation they are now. We can't go back in time and correct those missteps, but we can work to ensure the sustainability of our wildlife now in your backyard and around the world.

From butterflies to pronghorn, hummingbirds to black-footed ferrets, Mississippi kites to Mississippi gopher frogs and Louisiana pine snakes, they all have certain needs that must be met if they are to survive.

Species have done their best to adapt: nesting on the window ledges of skyscrapers in large cities when natural nest sites are gone, foraging at garbage dumps when natural food resources are depleted. The choices they've been forced to make to survive don't always work out well for us or them.

But, we can make the choice to help. Landscape your yard with plants that are friendly to native butterflies, bees and birds. Recycle it makes our natural resources last longer. Don't litter it hurts the environment and can be dangerous for wildlife. Hang bird nest boxes and bat boxes outside in appropriate areas.

For zoos, answering the challenge of sustainable captive populations means critically evaluating collections and adopting possible changes that may follow.

It also means a long-term view of the future with planned breeding to fill spaces already lined up at other zoos. In the past, zoos often were subjected to the boom-and-bust cycle.

A species was desired by other zoos so the breeding was ramped up. Eventually, the time came when there was no more room for offspring so the breeding was scaled down. Then it would come to the point where there were no animals available to fill open spots.

Hopefully, there still were animals capable of breeding, or in some cases, animals were available from the wild to rejuvenate the population, and the boom-and-bust cycle would start again. This cycle is one of the things zoos are trying to avoid with new management practices.

For Lee Richardson Zoo, the commitment to a focus on sustainable populations can best be illustrated by the noticeable changes in the bird collection.

Our Waldrapp ibis and most of our Taveta golden weavers were sent to other zoos that had the proper facilities for breeding groups.

We've brought in a female roadrunner to pair with the male we have here. Our boat-billed heron soon will be traveling to another zoo where there are females waiting for him.

Red-billed blue magpies, collared finch-billed bulbuls and more also have arrived at Lee Richardson Zoo as part of our effort to help develop sustainable populations.

By the way, our tropical birds will be moving to warmer quarters off exhibit in a month or so, so be sure to visit soon.

Visit our award-winning Web site at www.garden-city.org/zoo.