"Grooming is a social thing, a friendly thing, it calms chimpanzees down," says Jason Mier director of animal rights NGO Animals Lebanon.
As Mier talks, Omega, a 12 year old chimpanzee, picks through Mier's hair, occasionally yanking out the offending strand. It's one of the few displays of natural behavior that Omega has shown in over a decade.
Omega used to serve customers at a café in southern Lebanon until some got him drunk. As a result he turned aggressive, attacked some clients and was sold to a small, decrepit zoo.
Mier, who first met Omega six months ago, points to trash littering the floor of the 5m by 10m cage, a putrid blend of old food, water bottles and plastic bags.
"There is cement, there are metal bars, there is nothing natural whatsoever," he says.