"The Bear" is back in hibernation, after a week of stalking the forests, menacing Americans and plying his trade as President Reagan's great communicator.

Over at the Reagan reelection headquarters, they came secretly to love the big bad bear months ago. Over at the Mondale headquarters, in the past week, they came to grudgingly admire -- and politically fear -- him.

As a television persuader, this unique attempt at commercial by parable worked.

Reagan officials found in their focus-group tests involving average viewers that The Bear was an extraordinarily effective way to sell Reagan's peace-through-strength message.

And perhaps more convincing, Mondale officials discovered the same thing when they took the unusual step of testing the Reagan 30-second ad in one of their own focus-group experiments a week ago.

Reagan's angry bear aired nationwide during the past week.

In the ad, a bear is prowling the forest, mean, angry, hungry, as the voice of a narrator is heard: "There is a bear in the woods. For some people, the bear is easy to see. Others don't see it at all. Some people say the bear is tame. Others say it is vicious and dangerous. Since no one can really be sure who's right, isn't it smart to be as strong as the bear -- if there is a bear?"

A man appears, a rifle on his shoulder. The bear takes a slight step backward. And a simple written message is seen: "President Reagan. Prepared for Peace."

The ad never mentioned the Soviet Union, never mentioned Democratic presidential nominee Walter F. Mondale, never betrayed the fact that it was a political ad until the very end. Never mind -- the Reagan officials discovered in their focus group testing that viewers got the message.

The ad had the highest recall score of any of the Reagan ads tested in Reagan-conducted focus groups this year. Six of 10 people remembered seeing it. Three of 10 understood and remembered its message: that Reagan believes in being prepared to stand up to the threat of the Soviet bear -- and, implicitly, that Mondale somehow would not.

People watched the bear foraging with the sort of interest they would devote to, say, a scene from "The Wild Kingdom." Then they would talk with each other about what they had seen. And the next time the ad aired, they would watch it again.

The only downside to the ad, Reagan officials conceded, was that those who missed the parable often missed by a country mile. They usually came away thinking it was an ad about the environment.

It was back in May that The Bear was created by the Reagan campaign's Tuesday Team of ad experts by Hal Riney. It was a lone attempt at trying something different in that original Reagan package of "feel-good" ads.

Riney's previous work for Yamaha, Gallo and the Oakland A's, has given him an industry reputation for adding wry touches where others would opt for harder hits.

With The Bear, he adapted to politics a plaint he laid out to Advertising Age two years ago: "The beauty and the whimsy, the cleverness and the suggestion seem to be gone from everything. And it's been replaced by two people holding up a product they would never hold up and talking about it in a way no one ever talked and being astonished, pleased, delighted or surprised about characteristics of a product which in real life would actually rate no more than a grunt, at best."

Mondale officials privately give praise. "Their bear proved to be a soft, easy way for them to talk about a tough problem," said one Mondale official who had been informed of the results of the Mondale focus group that studied the Reagan ad. "Their problem was that people had fear responses to ads about nuclear war and defense and international strength. Their problem was -- how do you defend a hard-edged policy in a way that is widely accepted? The Bear did it for them."

Unencumbered by that problem, Mondale strategists used the opposite technique to dramatize the dangers of Reagan's "Star Wars" plan to introduce weapons into space.

"Star Wars worked very well for us because it frightened people, made them scared about a policy that is, in fact, scary," said the Mondale official. But, he conceded, Reagan's bear proved a worthy counter.