On a big Southeast Asian zoo trek last month,
@twilighter and I saw 4 wild primate species (Crab-eating Macaques, Pig-tailed Macaques, Dusky Langurs and White-thighed Surilis) in a variety of zoos, plus we heard wild gibbons as well. The Crab-eating Macaques are common everywhere in that part of the world, from backyards to zoos. Just at Khao Kheow Zoo (Thailand), we literally saw at least 500+ wild Crab-eating Macaques and to be honest they were a pain. If we left anything on the golf cart, which is what you need to get around that massive zoo, then the macaques would steal it and take off with their loot into the surrounding jungle. We had to get new water bottles after some macaques were sucking on ours! I loved seeing them as it added to the whole jungle atmosphere of the zoo, but I can sympathize with staff who have to deal with them on a daily basis.
At a couple of zoos, there's the use of some kind of 'gun' to scare off the rampaging monkeys. I'm not sure if KK Zoo was using an air gun or a pellet gun, but on two occasions I saw a keeper firing something at macaques as those primates were everywhere from the African Savanna to the kiddie playground. At other zoos, such as seeing Dusky Langurs at Lost World of Tambun and Zoo Melaka (two Malaysian facilities), the animals weren't much of a problem as they stayed in the canopy of the forest. Nevertheless, so many Asian zoos had monkeys everywhere, as well as wild deer, colugos and hornbills. We didn't see any wild King Cobras or pythons, but those snakes are apparently just as bad as the macaques because they are attracted to tamarins, marmosets, various birds and their eggs. A curator told us that if a big snake squeezes into an aviary, then every few days another bird will disappear and it's tricky for staff to locate the predator snake.