Tonight the pandas may overtake the sharks and the polar bears--this has nothing to do with New York street gangs or football teams--to become new ratings record-holders for a National Geographic Society Special. A grown panda could easily tear your arm off, and would under the right circumstances, but what an irresistible huge beast it is, one of the most charismatic and fascinating on the earth.

"Save the Panda," on public television's Channels 26 and 22 tonight at (or soon after) 8 o'clock, has an easy time making a case in behalf of its subject; it will essentially be preaching to converts, one assumes. Perhaps the Justice Department would like the show branded as pandering pro-panda propaganda just the same. Be all that as it may, this is another in the long line of splendidly edifying Geographic specials.

There are three words for such programs: wonderful, wonderful, wonderful.

As for the competitive side of this matter, it is strictly academic, yet we must take our broadcasting history where we find it. In a ranking of the highest-rated programs in PBS history, National Geographic Society Specials hold the top five places, including "Sharks" (January 1982) in second place and "Polar Bear Alert" (March 1982) in third. First place goes to the human race, via the Society's eye-popping 1975 special "The Incredible Machine."

It is conceivable tonight's panda show will be of sufficient popularity to cause the record books to be rewritten, if sufficient numbers of viewers have the patience to wait out the rigors of yet another fund-raising rite that will precede the scheduled telecast. First they flog the tattered tote bags, then they show the program.

Every species on the planet earth is endangered in a nuclear age, Homo sapiens key among them, and repeatedly hearing that this or that species faces possible extinction may become numbing after a while. But the panda, narrator Richard Basehart notes in the special, is "one of the most endangered species" of them all.

The great cuddly looking bear is also, according to the script by producer Miriam Birch, "mysterious and enigmatic," "elusive" and "reclusive." Studying the panda has been hard enough; preserving it will be even more difficult, because the terrain in which it thrives is disappearing. The loss of the panda would be, says field biologist George B. Schaller, "a disastrous moral blow to mankind."

And why? Just because they're cute? The giant panda has a particular dignity among animals, and a particular poignance. Perhaps it's the combination of the roly-poly girth (pandas are full-figured bears) and the melancholy teardrop eyes that seem to foresee some sort of doom just around the corner. What the program makes clear, not so much through what it says (and it says a bit too much) as through what it shows, is that an animal like the panda does more than decorate the earth. By its mere existence it enriches the experience of living here.

In the film, pandas do what pandas do. They munch bamboo and trundle around. Also, they loll a lot. And, in the case of the National Zoo's Ling-Ling and Hsing-Hsing, despite near-herculean efforts to encourage them, they stubbornly refuse to mate. A panda offspring has been produced in captivity in the Americas, however; the feat was accomplished in a zoo in Mexico where, it is pointed out, the male and female are permitted to cohabit year-round, which would seem to be nature's way. In Washington, where even the simplest and most natural things tend to get fouled up, the pandas are kept apart until mating season. It appears to have been a crucial mistake made by experts, one of the commonest phenomena in civilization.

The program also includes what the Society says is the first film ever made of a panda being captured in the wild, as part of a panda-tracking project in the bear's native China. A 235-pound panda lumbers innocently into the trap, gets jabbed with an immobilizing drug and suffers the comatose humiliation of being dragged out onto the ground and tagged with a beep-beep collar that will radio signals of its travels to the Chinese scientists, should they ever stop talking long enough to hear them.

Then, in another part of the same Chinese preserve, a group of American and Chinese scientists go to great lengths to inseminate artificially a panda named Li-Li. Basehart says the immobilizing drug given her doesn't hurt, but when jabbed, she lets out a roar that does not appear to mean, "Thanks, I needed that." After Li-Li has been put back into her cage, an American scientist says, "That was a good insemination," like a proud surrogate papa, and there is handshaking all around, but it doesn't take. The project ends in failure, and the panda is not pregnant. Indeed, she looks quite miffed and a trifle confused by the whole business. The quest goes on.

Produced in cooperation with the World Wildlife Fund, and including some gratuitous but diverting touristy footage of modern China, "Save the Panda" is another sterling achievement for the National Geographic Society; it is entertainment, expedition and enlightenment, produced with skill and care. A spokesman for the Society has taken pains to point out that Gulf Oil Corporation, in the eight years it has been underwriting the specials and including its commitment to support them through 1985, has committed in excess of $30 million to the project.

Good television is an endangered species, too; the Geographic specials help to preserve it.