She welcomes the orphan chimps of Zambia

In less than 20 years, Sheila Siddle has built the world's largest orphanage for chimpanzees in the backyard of her central African farm. She also cares for a menagerie of other unwanted or mistreated animals that have appeared on her doorstep, refusing to turn her back even on a baby hippo. Her mornings start at 5:30 a.m. and are consumed in feeding and nursing, mothering and nurturing her "family."

But don't mention retirement – or even a little time off – to this compact 70-year-old.

"You retire from a job, you retire from work. I don't think of what I do as work," she says in an interview in Boston, her first stop on a tour to promote her new autobiography "In My Family Tree" (Grove Press).

In 1972, when Mrs. Siddle and her husband, David, bought Chimfunshi (or "place of water,") it was no more than a fishing camp abutting the Upper Kafue River in Zambia. The Siddles turned it into a farm, starting out small – with some chickens. A few years later, looking for a challenge, they took on cattle.

Then in 1983, Pal – a frail orphaned chimp rescued by a game ranger as it was about to be sold as a pet – arrived at Chimfunshi. The Siddles knew almost nothing about chimps, and even less about animal conservation. "I hardly finished school," she says, laughing.

But the couple revived the malnourished Pal, and by 1984, game rangers had brought five more chimps to the Siddle farm, desperate to find them a safe home.

As word got out about their generosity, their brood continued to swell. Most chimps that come to the sanctuary are babies whose mothers have been killed by poachers.

According to the latest count, 93 chimps now live at the Chimfunshi Wildlife Orphanage, which has expanded to include two 500-acre enclosures and a staff of around 50. The Siddles, who hope to create the closest thing possible to a natural habitat for chimps, would like to double their enclosed area.

At times, though, Siddle's self-taught style has clashed with textbook knowledge about raising captive chimps. For example, she lets chimps at Chimfunshi mate freely, rather than controlling breeding.

For the most part, she says, instinct has guided her well. And as long as poaching continues, not only is she prepared to keep accepting newcomers, she sees no other way.

As she talks about the logging industry in Africa that is "massacring" trees and increasing hunters' access to forests, her weathered hands ball into fists. A century ago, she says, there were an estimated 3 million chimpanzees. Now, she doubts there are 100,000 left.

But chimps, which are officially endangered in Africa, are not her only worry. "It's all of Africa," she says in a way that erases any doubt that this native of England considers herself first and foremost an African.

Siddle left England in 1947, when her parents – slightly ahead of their time – decided to take the family on an extended trip. They bought five old army trucks and out of them fashioned one larger vehicle with enough room for beds for Siddle and her two brothers. – a precursor to the RV. The family headed south, by road and ferry, from Lancashire to Africa. She's returned to England only twice since.

Her years in Africa, however, have taught her the realities of hunting. "We used to have 70 elephants," she says, recalling the sight of the herd passing through her land. Now, that entire herd is gone. "Every one has been shot."