The 15-month-old was on the brink of death after he was kept in a chicken cage and fed nothing but condensed milk for the first year of his life. He had been kept as a pet in Ketapang, Indonesia, his caretakers said.
Now Budi is well enough to eat on his own, walk and climb.
"After weeks of physiotherapy, medical treatment and a nutritious diet, Budi's muscles are developing well," said United Kingdom-based International Animal Rescue
But Budi's development remains slow due to the extreme malnutrition, his caretakers said.
Budi was in quarantine for awhile, they said, but has been introduced to another infant orangutan, Jemmi, rescued by another shelter.
Neither orangutan had met another animal of its kind since being taken from their mothers just after birth, and they eyed each other with curiosity.
When Budi arrived at International Animal Rescue's Orangutan Rescue Center in Ketapang, his condition was extremely critical. His body was swollen with fluid due to a severe lack of protein. His limbs were misshapen because he was never fed properly.
Budi's "eyes fill with tears ever time he's moved by the doctors and he screams in pain," said Dr. Karmele Llano Sanchez, International Animal Rescue's program director in Indonesia. "It's really amazing that Budi has been able to survive this long."
It's unclear how Budi became someone's pet, said Dr. Ayu Handayani. The owner said that she was afraid to give the animal any fruit and believed that giving Budi only condensed milk was enough, Handayani said.
Eventually, the caretakers said, when Budi is strong enough, he will be released into the wild.