Polar Bear, St. Louis Zoo

You often hear people comparing zoos to modern-day arks.

I guess in the case of many species — those that are extinct in the wild or those that are found in tiny numbers — zoos are pretty much their last hope. The problem, though, is the numbers part.

If you start with a small number of animals in any given species, the odds of them dying off completely are high. Makes sense, right?

If you start with a large number of animals, the odds are much better.

So, here’s the problem.

Our Zoo has a lot of different species, but in many very important cases, we don’t have as many animals as we need to feel sure that we’ll have that species at our Zoo 15 or 20 or 50 years from now. That’s bad.

What can we do about it?

Well, the first thing is that we could cooperate with other zoos. We keep a few animals of a certain species, others keep a few, and when you add it all up, there’s enough to ensure that we’ll have them in zoos for the long-term future. And that’s exactly what we do.

Many species found in zoos here in the United States and also in zoos around the world are in what we call Species Survival Plans (or SSPs). For an SSP, we basically run a giant computerized dating service designed to encourage genetic diversity, keep inbreeding to a minimum and keep the number of animals to the maximum for a very, very long time.

I say a “very, very long time” because theoretically that 100-year clock resets every single day. Long story short, we want to keep them safe in zoos forever.

OK, we know that in order to be successful at keeping inbreeding to a minimum (and have plenty of animals), you must have quite a few animals to start with. How many is quite a few?

The number depends on how long the animals live, how often they reproduce, how many young they have and other variables.

Sadly, with some animals, their numbers are so small that we just allow them to breed without any concern for the genetic mix. That happened here with the addra gazelles many years ago. They had almost died out in American zoos and we, here in St. Louis, had the largest remaining herd.

Thanks to our Zoo, that species has rebounded in zoos across the country.

That’s critically important because addra, and other gazelles of the sub-Saharan reaches, are dangerously close to extinction. But, thanks to our Zoo, we should have enough animals to do a reintroduction back to the wild when the time is right. (By the way, it looks as though things turned out all right from a genetic point of view. We think we got lucky there.)

We had enough addra gazelles to bring the population size back up to a stable number, but that’s not always going to be the case. Let me give you an example using one of the most popular animals at the Zoo — Kali the polar bear.

In the late 1920s, American zoos began to exhibit and breed polar bears in earnest. Their numbers grew steadily because they bred well in zoos, but by the late 1980s, their numbers began to decline.

Zoos like ours decided polar bears needed better exhibits, so they stopped breeding polar bears and allowed existing ones to live out their lives. Long story short, on April 1 of this year, there were only 54 polar bears distributed among 29 American zoos.

However, only 39 of those were still young enough to reproduce. The natural mortality rate is about 4 percent per year. Put all that together and it’s predicted that we will have 29 bears left in 15 years.

Ideally, we’ll pair those bears up; however, with 29 bears for 29 institutions, that means that half of the zoos won’t have a bear.

Put another way, there’s a 50/50 chance that the Saint Louis Zoo won’t have a polar bear in 15 years.

What I’m driving at is this: Even if we cooperate with all the other zoos, all the zoos in the nation (or even the world) may not have enough animals right now in their respective zoos to ensure that we will have any given species around in zoos a long time from now.

Here’s the sad truth.

We have 579 different species in SSPs in North American zoos. Of those 579 species, 131 species are in the same category as Kali. For all practical intents and purposes, they will almost certainly disappear from zoos within the lifetime of a young child.

Only 47 species are species that we are pretty sure we will still have in zoos 100 years from now. The rest of those species, 320 of them are on the bubble.

If we did something about it now, we could ensure that we’ll still have them 100 years from now. If we don’t do something about it? Well, they’ll disappear. And that would be a tragedy.

So, what exactly would we do? The answer is pretty simple. We can take some of those 320 species that we’re not already too late to save and find enough space to breed them in places other than here at the Zoo.

For hoof-stock (think zebras, takin, wild asses and so forth), such a place would look a lot like a cattle ranch. For amphibians, we would take a totally different approach.

You know those cargo containers that are used on oceangoing ships? For $50,000, one can be converted into a home for frogs. It turns out that they’re just the right size to keep one species of a frog in large enough numbers that they’ll be around 100 years from now. We just add a little insulation, HVAC, plumbing and electrical, and a whole bunch of aquariums on racks. Efficient, bio-secure and a whole lot cheaper than a building.

Birds? Giant, but inexpensive aviaries. Cheetah? Simple enclosures with chain-link fence.

That’s what we would do.

If there’s not enough room in the ark — that is, if we have too many different species in the Zoo and not enough of any one species to ensure their survival in the Zoo — then we just build a bigger, more efficient ark.

We’ve already begun to figure out what it would cost to build a bigger ark, where we would build it, what species we’d put in it and what it would cost to run.

Of course the big questions are “Where would we get the money to build it?” and “Where will we get enough money to run it?”

We don’t have the answers to those two questions yet, but we’re pretty sure that we will need more support from our community to pull this off. One thing is certain though:

If we don’t figure out a way to do it, our children’s children may not ever forgive us. I hate the idea that my grandchild may never see a live polar bear at our Zoo. Or, for that matter, anywhere.