And then there are the tensions that arise among penguins anywhere, tensions that flow from the pursuit of love and, in a penguin sort of way, marriage. Inside this little man-made concrete exhibit -- designed to simulate the rocky islands off South Africa from which they originate -- philandering female penguins angle for better nests; jilted lovers pick up and move after a love-interest freezes them out; and love triangles are inevitable, complete with messy fallout and recrimination.

For many years, the keepers of the Brooklyn penguins believed that these romantic trials and tribulations took place only between the male and female penguins in the exhibit. Recently, however, they discovered that one more variation on the love theme was represented in the mix -- and had been there for years. A blood test revealed that Wendell and Cass, an inseparable pair of 15-year-olds known for a tidy nest and enduring lust, were both male. It didn't surprise the aquarium folks, but the media got excited and recently outed the adoring and oblivious couple.

On a recent chilly afternoon, there wasn't much to see in the penguin enclosure. It was bedtime, and only stragglers loitered in public view. A lonely bachelor scoped out the scene, and a couple waddled around together, perhaps going for a stroll before hitting the sack.

Wendell and Cass already had curled up together for the night, and they weren't coming out of their cozy burrow anytime soon, according to penguin keeper Stephanie Mitchell. Living monogamously in a high-rise nest above the rest of the crew, the guys tend to ignore the sexual high jinks going on down below.

Same-sex relationships in the animal kingdom are more common than most people think. In fact, in his 1999 book, "Biological Exuberance: Animal Homosexuality and Natural Diversity," biologist Bruce Bagemihl catalogs the unconventional sexual behaviors -- including bisexuality and transvestite tendencies -- of almost 200 different animals.

For this reason, says Mitchell, the aquarium staff wasn't particularly shocked by the revelation about Wendell and Cass' union. Other humans, however, seem endlessly curious about the relationship. In an interview at the aquarium, Mitchell talked about why Wendell and Cass are so devoted to each other, what the she-penguins on the prowl have to say about it, and how the whole affair went unnoticed for so long in the first place.

So do the female penguins seem to sense that Wendell and Cass don't want anything to do with them?

The females don't show an interest in all of the males; it's just a few of them that they like. Right now, we've got three out of 10 girls -- Ezmerelda, Gomez and Clarice -- who are experimenting with the availability of other males. That's 30 percent, which actually matches up with statistics that say that 30 to 40 percent of females will try to leave their mates and try to find other mates.

What happens?

Well, Gomez is a big flirt, and she just goes and visits with all these other males, and that causes Giovanni, her mate, a little bit of consternation. Ezmerelda has a little bit more of a situation with Old Man and Curly. Sometimes Old Man and Curly would fight with each other, but Curly's actually moved, so he's not really dealing with Ezmerelda anymore. I think he's given up.





That's how they flirt?

That's how they talk to each other. It's one of the body postures. Giovanni and Gomez are sitting with their backs to us. Curly just approached them and was like, "Hey, baby." And Gomez was like, "I don't think so."

Why they're sitting outside with the wind blowing, I'm not really sure. They should be inside.

This is cold for them?

It's a little windy. They're from South Africa.

What about the rest of the females? Are they in happy relationships?

They are in monogamous relationships, and they appear to be happy.

Do they show interest in Wendell and Cass that they would show to sister penguins? Any "Will and Grace" action in the pen?

No, they mostly stick with their mates. There's a few of the younger birds that you could call friends, but generally, once they pair-bond [mate monogamously for a full season], they just hang out in couples.

But the female penguins don't hit on Wendell and Cass?

No.

Does anyone?

No.

Why? Are they untouchable in some way? Would they get mad?

I don't know why the female penguins choose who they choose, or why the three females are having extramarital affairs, but they don't bother Wendell and Cass.

I read that Wendell and Cass have a particularly neat nest. Aren't females more attracted to potential mates with high-quality nests?

Possibly. The nest would show the fitness of the male and indicate that he's got a good location and he's going to be able to help the female out and keep her safe and provide her with young. And I would think that Wendell and Cass' nest was a prime nest site, and that the other females would be interested in it, but they don't seem to be.

Is it possible that they realize that Wendell and Cass are gay, and that they're not interested in offspring?

Any biologist will tell you that the purpose in getting together is to create young. But I don't know why they aren't interested in Wendell or Cass. This one other couple, Albert and Clarice, tries to get in their nest, though. This guy, Albert, sitting down front there, is one of a pair that tries to take it.

But Albert and Clarice are going for it as a couple, not because they're interested in Wendell and/or Cass. They just want the house.

Right.

What happens when Albert and Clarice try to take the nest?

Say, it's during a feeding, Albert and Clarice will run up to the nest and try to claim it. Wendell and Cass will come home and someone will just be there, waiting for them.

Do Wendell and Cass fight them off?

Cass mostly does the fighting. Sometimes they bite each other, or beat each other with their flippers. Wendell just runs away.

Why is Wendell and Cass' burrow considered prime real estate?

Your guess is as good as mine. Maybe because it's centrally located near the water and near the feeding station, two of the most important things for them.

How long have Wendell and Cass been living together up there?

Six or seven years.

And had they been with female penguins before?

No, they've always been with each other since they pair-bonded. They've never been with anyone else.

But you didn't suspect they were both male until when?

A couple of years ago. When I first started [working with them], I started thinking that they were both males based on their behavior. We did a blood test for other reasons and were able to determine that they were both male. [Blood tests are the only way to determine the sex of a penguin.]

What kind of behavior are you talking about?

Their sizes are similar to male sizes. Generally females are a bit smaller than the males. Females don't vocalize as much as the males do, they tend not to be as aggressive as the males are.

How do Wendell and Cass court each other?

They do it the same way a female and a male would do it. But generally, Cass will approach Wendell and do those postures called bowing. And they do something called flipper-slapping.

What does flipper-slapping look like?

The male usually comes up behind the female and hugs her and taps her with his flippers. And sometimes vocalizations are involved.

What does that sound like?

Like a donkey. I can't even imitate it. That's how they got the name "jackass" penguin. It's a braying sound.

So Cass and Wendell do this, too?

Yes. Mostly, I see Cass actually mating with Wendell, playing the male role, but we have seen Wendell mate with Cass.

Does one take o n the female role and one take on the male role in other ways?

Well, you know, that's a tough thing to say. Based on penguin characteristics, Cass tends to be more aggressive, more masculine. He does the male thing. Whether Wendell is with a male because he's a meek male, I don't know. But he's a 'fraidy-cat; he's afraid of his own shadow. He's a very difficult bird.

What do you mean?

He's really nervous, and it's hard to feed him and perform medical exams on him. He's a finicky eater. And though he's not aggressive toward the penguins, he's very wary of the keepers.

How do Wendell and Cass have sex?

They're doing the same thing as a male and female would, though obviously not producing any eggs. But the copulation is the same. I can give you specific details ...

Go ahead.

Penguins are birds and all the sexual organs are on the inside of their bodies -- it's called the cloaca. The urogenital opening is where they defecate as well as have sex. It's just this little hole in their rump area.

And it's called the cloacal kiss: What happens is that the female will lay on her belly and the male climbs on top with his feet and puts his rump around her rump and their cloacas meet each other, and then the sperm gets transferred into the female.

So Wendell and Cass do the same thing.

Right. Just without the eggs.

Is it fun?

No idea. We've never done a blood test to track brain activity or anything like that. There's no bodily reaction to mating like in some animals.

But they have an active, happy sex life?

A normal one. It's hard to tell. Some of the birds are exhibitionists and have sex right out in front of everybody else. Most of them will do it in their burrows. The only reason why we've known about [Wendell and Cass] is because on two occasions we've seen them copulating out on exhibit.[By this, Mitchell means that the penguins have sex outside of their burrows, for all penguins and people to see.]

What would make penguins do it on exhibit? Do they all have varying sex lives?

I don't know. Now's the time, you know that biological clock. Usually when the female is in her breeding period, she stays in her nest. Theoretically they're copulating a lot to increase the chances that they'll fertilize an egg. So there will be a 10- to 12-day period where the pair will stay in the nest and never come out.

Some of them have sex a lot. Burt and Moni have sex all the time. They have no problem copulating on exhibit. Others may not have sex practically at all. They could copulate all year round and some do, but their breeding season is November to March, so that would be the time when they would have the most sex.

Does that differ for Wendell and Cass since they're not trying to reproduce?

I can't remember what time of year it was when we saw them out on exhibit. It probably was either fall or spring because it was warm.

Have they expressed any longings to have young? Maybe they want to adopt?

Well, I think that if they did, they would have broken up. One reason why pairs do break up is because they aren't reproducing. Obviously, all animals need to reproduce. But [Wendell and Cass] don't seem to mind that they're not reproducing, so they don't need to break up, I guess.

Are there any babies in the exhibit? How do the adults treat them?

Not right now. After 100 days, a baby is just another bird to them. They're not treated very well by the adults because they look different -- the babies are all black for a while. Penguins pick on the birds that don't look like them. Like the ones that are molting.

[Another strange-looking penguin with a sort of ratty coat waddles out.]

Oh, naked boy.

What's his deal?

He has a molting problem. They molt their feathers once a year; they drop their feathers and grow new ones. Most of these birds are quite old, they're well into their 20s, and in the wild they live for 16 or 18 years. They can live up to 35 years in zoos and aquariums. Since they live longer here than in their wildlife span, things can happen. One of those things could be that their hormones get all wacky, just like ours do.

Right, like menopause or something.

He looks terrible. I feel so bad for him.

Might they start shacking up with penguins of the same sex when they're going through these hormonal changes?

There's so many reasons why they might. Wendell and Cass, though, got together when they were 3 or 4.

So, are same-sex relationships very rare, generally, among penguins?

I don't know penguin statistics, but it's not rare in the wild animal kingdom. There are a lot of same-sex relationships in the wild.

Are Wendell and Cass more monogamous than the rest of the penguins?

They're very in touch with each other. But there are a few couples that are sort of like that -- some are very dedicated. They seem to be one of the more dedicated couples. They're more aware of where the other is in the exhibit, they talk to each other a lot, probably a lot more than some of the other couples do.

They're just one of the best couples on the exhibit. Just a really nice couple.