Joy Adamson, whose book "Born Free" brought a new awareness of relations between man and animal to millions of people, was killed Thursday night by a large animal, believed to be a lion or leopard, at her remote camp in northern Kenya.

The announcement of her death yesterday said Adamson, 70, had gone for her usual evening stroll Thursday and had followed the trail of a lion seen earlier in the day. When she did not return, coworkers launched a search and found her body, mauled by a big cat, several hundred yards from the tents where she was conducting an experiment in returning tame leopards to the wild.

It was a similar experiment with a lion, named Elsa, that led 20 years ago to the publication of "Born Free," the simple but dramatic narrative of the more than two years that Adamson and her husband, George, spent with the big cat.

The book, and the subsequent movie and song of the same name, lent force to a then nascent movement to preserve African wildlife.

On another level, the popularity of her work is often cited as a premier example of man's continuing pull toward basic relationships in nature during a time increasingly complicated by industrial and technological growth.

"Born Free" and subsequent books by the Adamsons on similar themes provided clear and unique descriptions of an unusual relationship between human being and wild animal. In each of their studies, the Adamsons raised a wild cat from birth and then returned it to the wild, detailing at each phase their observations of the cat's behavior. In the process, they also provided insights into their own actions and emotions as they became attached to the cat and then moved to return it to its natural habitat.

Adamson was working on yet another study, this one of leopards, when she was killed Thursday night at her camp near the Shaba Game Reserve, about 200 miles north of Nairobi, the Kenyan capital.

The Associated Press reported from Nairobi that Ellis Monks, as associate of Adamson in conservation projects, said she usually took an evening strolll in the bush and, after more than 40 years of close contact with predators, did not think it dangerous. He said Adamson's killer probably was a lion, since lions were seen in the area, but that an attack by a leopard could not be ruled out.

Monks said Adamson's assistant, Kenyan Peter Morsen, and three others in the camp heard no sounds of an attack, but went to look for her when she did not return from her walk. He said they found her body with cuts on one arm and on the chest.

Announcement of her death was delayed until her husband, George, at another camp, could be informed. He had been severly mauled by a lion several months ago.

In a tribute isued in Geneva, the World Wildlife Fund said Mrs. Adamson made "a great contribution to public awareness and concern" for wild animals. "Although her main focus was on the wildlife of East Africa, her activities benefited wildlife everwhere and her loss will be felt worldwide."

The Adamsons turned the proceeds from their books and movies over to the Elsa Wildlife Trust, which has raised millions of dollars to foster wildlife conservation. Her worldwide lectures, as well as her books, served the dual cause of animal preservation and scientific observation of animal behavior.

Born in Austria, Adamson came to Kenya, then a British colony, in 1937. She had been trained in the arts and begun to paint the indigenous flowers.During her first 10 years in Kenya, she once said, "I did nothing but paint flowers. There are seven times more plants in Kenya than in all of Europe."

Many of her more then 4,000 paintings of indigenous flowers, animals and tribal life hang in Kenya's National Museum in Nairobi and her books are full of her drawings and photographs of the animals, mountains and hauntingly beautiful savannah of her adopted homeland.

George Adamson was a game warden in charge of a vast region of northern Kenya when the two met and subsequently married in 1944. It was her third marriage.

In 1956, the Adamsons adopted Elsa after the three-day-old cub's mother had been killed in self-defense by George Adamson.

Believing, as George Adamson once said, that "the mentality that condones keeping wild animals in lifelong captivity is little removed from the mentality that condoned the slave trade," the two lavished their love on the cub but also taught it to hunt, believing that one day they would try to return it to the wild.

When the time came to release the cat more than two years later, it proved to be an emotionally draining experience for the Adamsons, and apparently a trying one for Elsa, for the cat returned over more than 300 miles to a point near its birthplace, and near the Adamson camp. There, close to the people who raised her, Elsa thrived, bore cubs of her own, and frequently came to visit with the Adamsons.

All this is faithfully recorded in "Born Free" and the subsequent books that followed both Elsa and her offspring, and similar experiments with other cats.

"Elsa could control her cubs from a distance of 180 miles," Mrs. Adamson once said in an interview. "The bat taught us radar and we learned sonar from marine animals. Life is interwoven and men need animals, possibly more than animals need men."

Shortly after achieving fame for her work with and about Elsa, Adamson said of her experiments:

'I not only want to breed animals under natural conditions so that they will survive after they have become endangered by man's influence . . . I also want to learn from them where man can play a more constructive part in the balance of nature -- and thus survive himself."

Even in her later years, the experiments continued. She ended her autobiography, published this past spring, by referring to her latest work with leopards.

She recalled an encounter with a park ranger in October 1976 who told her he was lookng after a one-month-old leopard cub.

"The cub is now in my care," she wrote. "From the moment of Penny's arrival, a new chapter in my life began."

She was completing that study when she was killed by a marauding cat Thursday night.