Wild macaques don't abandon babies. So why did Punch's mother?

Wait 5 sec.

Little Punch, a seven-month-old Japanese macaque living in the Ichikawa City Zoo in Japan, has captured hearts on the internet. Abandoned by his mother in the first few days of his life and raised by the keepers at the zoo, he has had some trouble integrating into the group of around 60 Japanese macaques.