There are famous grudges in history: Rome vs. Carthage, Tesla vs. Edison, Minnesota vs. Wisconsin. You can explain them with history, politics, human nature. Nothing explains the vicious quarrel between dogs and raccoons.

Nothing we know, that is.

Dogs will chase squirrels and voles and rabbits, but it’s just business as usual. Nothing personal.

But raccoons seem to bring out some primal hatred in dogs that turns them into spittle-flecked maniacs, and makes you realize that beneath your pet’s lovable-goofus personality is bloodlust born of an ancient feud.

A few nights ago, our dog Birch bolted from the back stairs to the big tree, where I saw a huge striped beast going up the trunk. This guy was set for a long winter. He was so big that I could almost hear his belly slosh as he climbed. When he got to a fork in the branches, he peered down with aloof indifference at Birch, who was barking unceasingly.

I got out a flashlight to see if the raccoon had wandered up and away. They sometimes seem to climb up until they disappear from view entirely, a trick only otherwise accomplished by college administrators. But, no, there he was, glaring down at the dog and me.

Eventually, the dog calmed down and the peril passed, as they all do. We went inside so Birch could nurse his grievance — until he fell asleep.

A few hours later, he wanted to go out because Out is where dogs want to be, so they can decide that they would rather be In.

A few minutes after I let him out, I heard my wife call my name in alarm from downstairs. People in the plane passing overhead heard her. Whales in the deep Pacific heard her. I ran out to find Birch and the raccoon combined in a snarling, spitting, screaming ball of murder.

The first thing I thought: rabies!

I was thinking of the dog, at first. And then I started to wonder if I was supposed to get rabies shots. Were they like flu shots?

And then I remembered the stories from childhood about the kid who got bit by a rabid dog and had to have 12 painful shots in the stomach!

That took about five seconds.

Then I grabbed Birch by the tail and collar and yanked him back without him biting me. But the raccoon lunged forward to keep the fight going.

Finally got Birch restrained, and the raccoon lumbered away, screaming curses.

We went inside, where I got antibiotic salve and tended to Birch’s cuts. In a way, I felt proud of the hound. Eating a bunny last summer, that was stupid. This was an epic battle against a serious foe.

The next day, I took Birch to the vet, just in case.

He didn’t have any bites and his shots were up to date. But the vet decided to give him some distemper meds, just in case.

The vet said rabies wasn’t common in Minnesota raccoons this time of year, but distemper, maybe.

Distemper was a good characterization of the entire engagement.

“My golden isn’t bothered by anything,” one of the vet assistants chimed in. “Squirrels, other people, he’s ‘Whatever.’ But a raccoon makes him turn into a feral beast.”

We might never know why.

It’s possible raccoons smell like mail carriers. It’s possible that mail carriers smell like raccoons. It’s possible that a mail carrier who showed up wearing an eye mask, a striped shirt and a bushy tail would make even an elderly rug-dog go for the neck. But mail carriers never dress like that.

Perhaps they know something we don’t about ancient grudges in the animal kingdom.