A cautionary tale for the supposedly knowledgeable:

As I was making my way around the city over the last year or so, I began to smell skunk.

I smelled it everywhere. On the streets as I was biking. On sidewalks in the Loop. On the "L."

A friend of mine had been smelling it too — inside her apartment in a high-rise. She planned to ask the building's management to locate the skunks and evict them.

Well, I'm an urban wildlife kind of gal. I know we share our city with coyotes, opossums, even foxes. Note to self, I thought: Find out and write story on why Chicago is being invaded by skunks.

One day on the North Avenue bus, I found myself sitting amid particular pungency.

"Can you believe it?" I asked the two young women sitting next to me. "So many skunks in the city lately!"

They glanced at each other, then back at me. They seemed to be trying not to laugh.

"That is the smell of skunk, isn't it?" I said, somewhat uncertainly.

"No, it isn't," one of the women murmured.

Not skunk? With that distinct smell?

"What is it then?" I asked.

They hesitated. Finally, one of them volunteered an answer, of sorts.

"It's … life," she said.

Life?

I left the bus mystified, but with a growing sense that I was smelling something other than skunk.

My CTA-mates had been youthful, so I sought out a young person I knew and asked:

Is there something around that smells like skunk but isn't skunk?

Sniggering, chortling, then finally the answer.

Friends, if you think you know what marijuana smells like because you smelled it yourself in your possibly misspent youth, this news is for you:

It doesn't necessarily smell like that any more.

"The smell has changed," said Ryan Vandrey, a behavioral pharmacologist and assistant professor at the Johns Hopkins University School of Medicine who has studied marijuana for 12 years.

"Marijuana entrepreneurs have developed specific strains of marijuana that contain attractive characteristics," he said. "In some cases they'll breed them to have unique smells and tastes; in other cases, certain potencies or balances of chemicals."

"There's a whole range of smells. There are strains that have fruity aromas and fruity tastes and names like bubble gum and blueberry and grape."

"It's similar to how there are different strains of tomatoes," said Dan Linn, executive director of the Illinois chapter of the National Organization for the Reform of Marijuana Laws. "The demand and the marketing have yielded this industry where it's more profitable to be able to have different varieties and different offerings for these consumers."

So what's with the skunk?

"I don't think they went out and said 'Let's develop a marijuana that smells like a skunk,'" Vandrey said.

"Rather, I think that at some point in the genealogy of marijuana growing and development, there was a strain that came along that was extremely potent and gave people a good high and happened to smell like a skunk."

That smell became associated with a powerful high, making for a powerful marketing tool. A brand was born.

"It's been around for probably 20 years now, but it's ... getting more and more popular," Linn said. "With the advancements growers are able to use to produce these products, more people have more options. And these days, he said, "more people are preferring the varieties that smell like skunk."

These strains, which are called by names like "Skunk Bud" or "Super Skunk," are not necessarily more potent, Vandrey said. There are too many varieties to support a universal claim.

Still, "skunky-smelling marijuana is among the more popular brands," he said.

So what happened to the old familiar smell, that eau-de-park-across-from-high-school-at-lunchtime?

It's still there, in traditional strains and in less sharply scented ones, he said. Most people who have smelled classic pot would recognize most kinds of current pot.

But the skunk variety is a dead ringer for skunk.

My friend's apartment building was not infested with skunks. Her husband figured that out when he realized that their windows faced their stoner neighbor's balcony.

And the city is not being overrun with skunks, though apparently it is pretty well-stocked with weed-smokers.

The other day I got into an elevator in an office building with a woman my age and a clean-cut young man carrying a gym bag.

She sniffed.

"How did a skunk get into an elevator?" she asked.

The guy busied himself with his cellphone.

I shrugged. "These days it seems like they're everywhere," I said.

blbrotman@tribune.com