Sometimes Kam Ying stares at the empty bed her master used to sleep in or looks at the door as if she thinks he may come home.
It has been three years since 'Monkey Man' Chan Yat-biu died, but his former pet and constant companion still seems to miss him.
'My father and Kam Ying were very close,' said Chan's son, Chan Yiu-wing, 54. 'He saw her more than me. They communicated by just looking at each other's faces.'
Mr Chan has taken care of the 10-year-old rhesus macaque since his father, who raised the monkey from a baby, died in 2004.
He says he wouldn't risk taking Kam Ying to visit his father's ashes at the Tseung Kwan O columbarium - even if the Food and Environmental Hygiene Department would allow it, which he doubts - for fear of upsetting her.
'I dare not take her to visit my father's niche. She has kept emotions for my father and misses him very much. I am afraid that she would be too sad and come home out of control and get sick.' He keeps pictures of his father out of Kam Ying's sight.