AUGUSTA, Maine (AP) _ Attempts to reintroduce caribou to Maine have been thwarted by disease and bears, but based on the success of a hearty doe named Daisy, officials will keep trying to ''transplant'' animals from Canada.

''We were amazed she was in as good condition as she was in'' after a 600- mile trek into and out of Canada, said wildlife biologist Mark McCollough, leader of the privately funded Maine Caribou Project.

Of a dozen North American reindeer released last spring in Baxter State Park, only Daisy is known to be alive, although a second caribou that lost its radio collar may also be, said Richard B. Anderson, project coordinator.

Five caribou died after being attacked by bears, and five died of the ''brainworm'' parasite. Others still being kept in pens have been ravaged by brainworm and ulcers, said Anderson. More than two dozen caribou that were used as a breeding herd remain in pens at the University of Maine at Orono.

Despite the troubles encountered by most of the herd, Daisy's experience ''shows they can thrive'' in Maine, where caribou were hunted out of the state around the turn of the century, McCollough said. Sightings and radio tracking mark a trek from the wilderness park in central Maine to Quebec and back.

Daisy ''encountered everything possible,'' said Anderson. It crossed highways, stayed healthy, undoubtedly survived meeting bears and coyotes, ''and when we caught it, was in just as good shape as when we let it go.''

Two dozen caribou were shot with tranquilizer darts in Newfoundland three years ago, rounded up on helicopters and trucked 1,200 miles to Maine. Project leaders now have asked Canada for 25 more caribou in 1990 and - if all goes well - for another 25 in 1991 and in 1992.

Newfoundland's environmental and lands minister, Jim Kelland, agreed Wednesday to give the project up to 75 caribou. ''It's something when you can share a bountiful resource that you have with some other area that has been deprived for one reason or another,'' he said.

''This is a great Christmas present to all the people in the United States who believe that it's important to make a commitment to restore native wildlife species,'' said Anderson, a former Maine conservation commissioner.

The Maine Caribou Project wants to release about 50 caribou - including most of those in the pens and those shipped from Canada - next year.

It would be the third release attempt. In 1963, two dozen Newfoundland caribou were released in Baxter, but they disappeared, possibly as a result of poaching, disease, predation and dispersal. Poaching is no longer considered a major threat, thanks to stiff new fines and jail terms for killing a caribou.

Biologists have learned a lot from the setbacks of the latest attempt, Anderson said. For example, they learned that shots are more effective against brainworm than putting medication in the caribous' food. They also learned that bears are more likely to attack caribou than had been thought, and that bears tend to attack their prey's face, while coyotes attack the hindquarters.

Another lesson is that the caribou should not be kept in pens before being released because they do not learn to defend themselves. And it appears caribou are more prone to brainworm while in captivity, McCollough said.

If caribou are released again, it will probably be in higher elevations, where they are less likely to come in contact with deer infected by brainworm and they may fare better against predators, he said.

Biologists are even rethinking the way they should capture the caribou. Some animals died as a result of a tranquilizing drug that had varying results on different animals shot w ith darts during the December 1986 roundup.

While they are using a new drug, Newfoundland wildlife officials are also experimenting with a roundup method used by Scandanavians in herding reindeer - driving caribou into a large, funnel-shaped corral. Another possible plan is to drive them into a lake and catch them while they are swimming.