NYARU MENTENG, Indonesia — Katty, a docile, orange-haired preschooler, fell from a tree with a thump. Her teacher quickly picked her up, dusted off her bottom, refastened her white disposable diaper and placed her back on a branch more than seven feet off the ground.

Katty is an orangutan, about 9 months old, whose family is believed to have been killed by the huge fires last fall in the Indonesian regions of Borneo and Sumatra. The blazes are an annual occurrence, when farmers clear land by burning it, often for palm oil plantations. But last year’s fires were the worst on record, and scientists blamed a prolonged drought and the effects of El Niño.

The blazes destroyed more than 10,000 square miles of forests, blanketing large parts of Southeast Asia in a toxic haze for weeks, sickening hundreds of thousands of people and, according to the World Bank, causing $16 billion in economic losses.

They also killed at least nine orangutans, the endangered apes native to the rain forests of Borneo and Sumatra. More than 100, trapped by the loss of habitat or found wandering near villages, had to be relocated. Seven orphans, including five infants, were rescued and taken to rehabilitation centers here.