"Are men naturally monogamous?"

Auckland's king of the swingers Rod Jackson, 51, snorts at the question.

"Hell no - men haven't been monogamous since we came down from the trees. To make a man monogamous is like asking a gorilla to do brain surgery. He's got hands and a brain, but there's no way he can do it. He's not equipped. It's the same with men - they try and they fail miserably."

Jackson runs Auckland's swing-Mecca, Club Sparty, with wife, Sharon, 44 (the couple have been together 18 years, swinging for 16). Wonderfully gregarious, the IT-worker (by day) is, by night, an authority on the furtive sexual lives of Aotearovian men.

"Hmm, have I got a lot of secrets in my head," he says, laughing maniacally. "You would not credit the conversations I have. I know a lot about a lot of people. A little bit of liquor, a little bit of sex, loosens the tongue."

But these secret lives are not, well, always so secret. Take three high-profile men whose high jinks have recently been splashed all over the press. Herman Rockefeller, ex-New Zealand businessman and church-going chum of the Prime Minister, was allegedly murdered last month by a swinging couple from a second life of which his family knew nothing.

And of course, there's Tiger Woods, who gave new meaning to his sponsor's slogan Just Do It when he racked up at least 19 mistresses, and somehow, bizarrely, thought he could keep it quiet.

Then John Terry, captain of the England football team, was sacked yesterday after being caught in the sack with his team mate's lingerie model girlfriend, Vanessa Perroncel.

These are the just the latest in a line of duplicitous rooters that stretches back to antiquity. For an all-time world champ, it's hard to look past Gaius Caesar Augustus Germanicus (Caligula) who, said Roman scribe Suetonius, "made advances to almost every woman of rank in Rome" during his chaotic four-year reign. Then there's Henry VIII, whose wives infamously paid for his infidelity with their heads.

While the modern concept of marriage, at least in the West, has become a more equal partnership, the chicanery continues. Numerous American presidents have lived by Henry Kissinger's aphorism that "power is the ultimate aphrodisiac".

JFK, implausibly, claimed to get afternoon migraines if he wasn't "seen to", while Bubba Clinton publicly avowed that he did not have sexual relations with that woman. Warren Beatty recently denied a biographer's claim that he'd notched 12,000 conquests; NBA star Wilt Chamberlain has proudly claimed 30,000. And let's not even go there with those unctuous televangelists.

It's not just the rich, famous and powerful sharing the love. Sociology professor Dr Curtis Bergstrand wrote Swinging in America: Love, Sex, and Marriage in the 21st Century based on 40 years' research. He found swinging had infiltrated mainstream society.

Speaking from Bellarmine University in Louisville, Kentucky, Dr Bergstrand tells us the swinger's demographic is not the ageing hippies you might expect. "White, middle-class, professional, church members. Married an average of 10 years," he says.

He argues that "non-monogamous relationships such as swinging and polyamory offer a new blueprint for combining sex and love - one that may prove more in line with the way people actually live their lives in our society."

The University of Auckland's Virginia Braun, a senior psychology lecturer specialising in sex and sexuality, agrees that monogamy is a problematic concept.

"We as a society place enormous value on monogamy," she says.

"At the same time we locate sexuality as centrally important to our identity and well-being as individual human beings. This means any transgression of this is typically framed as the worst thing that can be done to a person, and ... treated with incredulity, suspicion or outrage."

And that's why you won't get many men prepared to go on the record. "Swingers are like possums," Jackson says, laughing. "They know who they are, what they are, but they're very shy. And they only come out at night.

"Pretty much the only swinger in New Zealand who's happy to be named is me!"

They frequent dens of iniquity such as Auckland CKK (Club Kit Kat), The Scene, Club Silverado in Wellington, Club Se in Christchurch ("professionally cleaned and disinfected to a very high grade before we open") and others.

But it's Club Sparty on Auckland's Cross St, off K Rd, that's the hotbed of action. Unlike other clubs, it's licensed as an adult entertainment centre and has a bar, dance floor, bedrooms (one with an L-shaped bed that can fit 10 couples), private nooks, and spa pool and sauna. There are baskets of free condoms, "heaps of clean, small towels" and the sheets, of course, are changed daily.

Jackson, with a salesman's patter, notes: "Not only are certain types of behaviour allowed in our clubs, we specifically encourage it."

Sparty is open three nights a week - Thursday through to Saturday. The door charge is $50 per couple; $75 a couple after 10pm.

Sole traders? Single women are free: "Oooooh, yeah!" Jackson exclaims. "I'm not stupid."

Single men, on the other hand, are like the male chicks fed through the macerator. Says Jackson: "They're pariahs in the swinging scene. Because there's so many of them just trying to get laid. Let's face it."

Nevertheless, he'll allow a few in on Thursdays if they're needed to even up numbers - and prepared to pay $100.

"They've gotta wanna. They can't just rock up to the door and say 'Here I am' ... they've gotta put a bit of effort in."

Having indicated their interest, the single men wait, usually in nearby bars until they get a text from Rod's wife, Sharon. "It's a holding pattern," Jackson says. And very popular: on any given night, they might have a dozen guys waiting in reserve. Waiting for that text. Waiting to join the 15 or so pairs already in action at Sparty.

But regulars get first dibs. "They'll contact Sharon on the night and say 'Hey, what's tonight looking like?"'

And she'll say: "Oh we've got heaps of couples - I thought you'd never ring.

"Get your arse down here."

Once you're inside, what can you expect? What can you do?

"What can't you do? Everything goes - so long as it's consensual. Basically it's down to the woman's own rules, but we pretty much frown on sex at the bar. It's just messy - I mean, we're serving drinks and food there. It's like: 'Put that away will you?"'

Jackson reiterates the importance of consent: "No means no: if a woman says 'no', then it's game over."

Who are these men?

Jackson: "They tend to be Caucasian upper/middle class.

"I wish I could say they were single, but sadly that's not the case."

Not so much single men as flying solo for the night.

"We have the same discretion as a brothel. We don't condone, but we don't judge. We don't ask, we don't tell. What happens at the club stays at the club."

But he does find himself in difficult situations. "There are so many strange goings-on that I've learnt to be a bit of an actor. Act surprised when it's required.

"I've had guys come down by themselves, and then they'll bring their wives in and I have to act like I've never seen him before. Or the girl he's with is not the girl from last time. She might be the fourth.

"Men have many different reasons for doing swingers' clubs, for going to a parlour, for going to a pub and picking up a single girl. I'm not one to judge because God knows I can't!"

YET, IT'S not the swingers' clubs where most of the action's at. Men looking for sex outside their relationships are increasingly looking online.

US-based swingers and adult personals website adultfriendfinder.com has almost 32 million members worldwide, including nearly 184,000 New Zealanders. Hornymatches.com - "Sex Personals and Beyond" - has 74,000 Kiwis: a staggering 67,135 are men seeking women, just 1549 women seeking men.

But the big daddy of them all is nzdating.com with a quarter of a million members, including tens of thousands seeking sexual meetings only.

We set up a fake profile as a 24-year-old Aucklander, CuriosityGirl, who was in a relationship and looking for a man in the same boat: married or in a long-term relationship. Said CuriosityGirl: "I have no intention of leaving my partner but he isn't delivering the goods.

"Discretion," she insisted, "is a must."

The response was overwhelming - 100 mails in the first hour, two every minute when she was online. Less than a day into her existence, CuriosityGirl had received more than 500 "applications" from rooters.

In Curiosity's profile, we repeatedly stressed that our applicants must be in a relationship and so were surprised to receive missives from lads whose profiles said they were single.

"just because it says im single doesnt mean i am," said one dreadlocked 23-year-old from the Shore. "i have a gf just gotta b sly ..." Two men had to jump off the computer in a hurry, one noting "she's here... got to go"; another sent a pic of him and his unaware girlfriend. Clearly we weren't the only ones being deceptive.

Most of our applicants were older. Some were first-timers, others seasoned pros. Some suggested places to meet: "a secret underground pad", outdoors, motels or their place while their partners were at work. Perhaps spooked by Tiger Woods' unravelling, many suggested chatting by email or MSN, rather than text or phone. Some had a secret second phone or planned to put CuriosityGirl in their phone under a guy's name - and suggested we do the reverse with their number.

However, some expressed great affection for their partners. Seven were about to get married. Only a couple expressed any reservations: "my gf doesn't know aye," said one. "i know its f***ed up."

But far, far more seemed to find the game perfectly acceptable. "Honesty gets us everywhere," said one businessman. "Just don't tell my wife!"

Not all were sleazebags - there were a couple of nice-sounding, genuine-seeming guys. Most said sex had become boring with their partner - "nice girl sex is crap" said one - with several claiming they hadn't had sex in months. From what we could tell, only two from the 500-plus had agreed to an open relationship with their partners.

They're in fine company: "I doubt that fidelity is absolutely essential for a relationship," Angelina Jolie told German magazine Das Neue. "Neither Brad nor I have ever claimed that living together means to be chained together."

Although we stressed discretion, nearly all our applicants sent in face-shots and some sent in personal information (email addresses, mobile phone numbers and more ... all unsought).

Auckland's a small town - we recognised two.

Several helpfully sent photos of their "equipment", a Coke can set alongside to give a sense of scale.

"Some of the men who go online are honest that they're in a relationship and looking for sex outside of it," says Dr Michelle Mars. But the sexologist and former Massey University lecturer, who studies the sociology of sex and runs practice Sassi-inc.com from Wellington, admits some lie online. "They'll say they're single. They'll establish a fake emotional relationship to get sex."

Most of these online Lotharios, she says, are men who've been in monogamous relationships for some time. Who are bored in the bedroom.

But it's a big myth, Mars says, that men want more sex than women. "Men talk to me about not getting the variety they want." Variety within the relationship - or outside of it. The thrill of the new.

Without the girlfriends finding out. "It's quite common for men to have one phone for the main people who contact them, and another for when they get a little bit drunk and horny. And they'll quite often go out of town." Beware the 'business trip'.

But that doesn't mean these guys are feeling good about cheating on their partners. "Often they're quite torn about looking for sex elsewhere," says Mars, "and aren't comfortable with it."

While there are plenty of Mars-Venus theories as to why men are more promiscuous and women, generally, more faithful (eg, men need to spread seed about to ensure survival of their genetic line; women want to be looked after), the evidence suggest there's a fair element of conditioning involved. "It's a social expectation of the world we live in," says Mars. "Ducks are monogamous - not people."

Jackson agrees and says it's not just men who can get a taste for polyamory. "I've met over 4000 couples and I've seen the downside when a woman is introduced into swinging and found there's a bigger sex life out there than what she's got with her husband. I've seen it all turn out disastrous. People really, really need to understand what they're playing with.

"What actually happens in a swinging relationship is that the power shifts, slightly, to the woman. Once you open Pandora's Box, the power shifts and the man isn't as much in control as he thought."

Dr Bergstrand concurs: "Women enjoy it more because they are not as competitive as men in this setting."

And the good doctor reckons we should relax a little about monogamy. He even has some sympathy for a certain errant golfer. "Lifetime monogamy takes a lot of self-control. Even if you are married to the most beautiful woman in the world you are still going to desire variety eventually."

Anthropologist Helen Fisher suggests we are genetically programmed to lose interest in a sex partner after about four years like much of the animal world.

Bergstrand says "I personally think we suppress sex too much in our society and it tends to explode sometimes in destructive ways."