Here's San Francisco Mayor Gavin Newsom:

"People like pit bulls, but there's a reason we don't have polar bears or mountain lions in the city."

I see several problems with this comparison. Let's start with the polar bears. San Francisco not only has them, they run sex ads for them:

"Single white female needs mate."

As personal ads go, it's simple and understated. Aspiring matchmaker Deb Cano jokes that it couldn't hurt. Although her candidate is only 23, her biological clock is ticking. And there's another problem, too: Ulu, a onetime provocateur, might be more than most males could handle.

Still, Cano -- an animal keeper at the San Francisco Zoo -- is undeterred. She's hoping a betrothal might materialize at a four-day meeting of the International Polar Bear Husbandry Conference, which begins Wednesday in San Diego.

On the whole, polar bear courtships at the San Francisco Zoo have not gone smoothly.

Two years ago, a Wisconsin polar bear destined for Ulu's lair had some medical issues that eventually doomed his transfer.

Two decades ago, Andy and Pike, the zoo's two other polar bears, were supposed to mate someday. Andy, born in Atlanta and named after then-Mayor Andrew Young, was imported as a companion for Pike (pronounced pee-ka), a female born at the San Francisco Zoo. They turned out to be a same-sex couple when it was finally discovered that Andy was a girl.

No wonder he's denying they exist.

In fairness to Newsom, he probably doesn't mean all polar bears; just wild ones. The kind that would run around loose and rifle through people's trashcans, make off with the family pet, and waylay the occasional hiker or two. Is he suggesting that existing laws don't already allow the city to deal with dogs that do that? San Francisco has leash laws, a vicious dog ordinance, a well-financed animal control agency, and packs of lawyers who'd be all too delighted to go after the owner of any dangerous dog.

The polar bear comparison, therefore, is as factually false as it is metaphorically inapt. Frankly, Bush is more like Trotsky than pit bulls are like polar bears. At least Bush and Trotsky are both members of the same species... (and please no wisecracks about that, OK?)

But what about the mountain lions? They might not be limited to the San Francisco Zoo! That's because mountain lions have already attacked and killed California hikers and there have been repeated sightings and incidents right in the San Francisco Bay Area -- including places such as San Jose, Palo Alto, and Oakland. (Perhaps they can change the name of nearby suburban Mountain View to Mountain Lion View.)

Most intriguing to me is this disappearing report of a mountain lion sighting in South San Francisco.

The driver -- whose name will not be released by California Fish and Game officials until their investigation is closed -- spotted what appeared to be a mountain lion behind Forbes Boulevard businesses, said police Cpl. Mike Toscano, who reported to the scene.

Although six South City police officers arrived on the scene within three minutes of the 7:52 a.m. phone call, none was able to find the animal after combing the area, said Toscano, who explained that the Peninsula Humane Society and California Fish and Game were immediately notified.

I'd be surprised if they did, especially considering that when police shot a mountain lion menacing children in the San Francisco suburb of Palo Alto, instead of being thanked as heroes, they were compared to the Americans at Abu Ghraib.

I guess by Newsom's standards, that's another fair comparison.