The Bronx Zoo, the largest city zoo in the country, is facing $15 million in budget cuts, and so hundreds of animals are being evicted.

It's a real loss. The 114-year-old zoo, run by the Wildlife Conservation Society, is getting rid of animals based partly on which ones are popular with its 2.1 million annual visitors. That means four exhibits and a whole slew of rare animals are on the chopping block (only figuratively -- don't worry). Unique creatures like the Arabian oryx and blesbok, two types of antelope, must go. In fact, the zoo's whole Rare Animal Range will soon go, as will foxes, deer, and the guanaco, a relation of the llama. More common animals like elephants and giraffes can stay because kids like them.

And thus, by catering to popularity, a zoo gets dumbed down, hampering its educational mandate.

One exhibit due to close is a particular favorite of mine: The World of Darkness, an enclosed pavilion where legions of nocturnal animals such as bush babies, bats, night monkeys, and lemurs can be viewed in low light. I have always considered the stars of the Bronx Zoo to be the naked mole rats, who troop blindly though tubing like ants in an ant farm. They're homeless now, too. Considering that a huge percentage of the world's animals is most active at night, it's another big blow to zoological education.

The zoo is planning to add hyenas and aardvarks (and, of course, a new kids' area), but the net loss is depressing. The 265-acre zoo can't just release the newly homeless critters into the city -- the alligators in New York City's sewers would devour them whole -- so they're being shipped to other zoos. Hopefully they can afford them.

Like many businesses around the world, the Bronx Zoo is finding itself in a pickle: It has to trim features because it's not drawing enough money (corporate donations are way down), but the loss of those features can only decrease its value, leading to fewer visitors yet.

Without wise stewardship, it's likely to be the beginning of a death spiral. Or even the middle of one: In January, the cost-cutting zoo shut down its popular Skyfari ride, one of those classic bucket gondolas that so many American amusement parks used to have. It was the zoo's third-most popular attraction, but it cost too much to maintain. Now, you can count the number of American parks with bucket rides on one hand (Busch Gardens in Tampa is one. Both of Disney's are gone.)

Darwin theorized about the survival of the fittest in the wild. With zoos favoring the popular creatures, it's a danger inside our animal sanctuaries, too.