Cefn Yr Erw is pretty strapped for cash you know. They need all the help they can get for site maintenance. Since many of the primates are ex-circus, the owners puts their old skills to good use. This is actually a ride-on mower and in exchange for mowing the grass, the gibbon gets a banana. By the looks of it, he's probably a bit hungry by now.
If they had the cash they could possibly divide up this enclosure into smaller segments to inhabit other primates. the lemurs for example would appretiate a bigger enclosure that was open. they spend more time on the floor then gibbons for sure.