The Pigman feeds Bobo peanuts. I do not believe he feeds him hot dogs.
When Bobo, "the ugliest, most vicous-looking baboon (Lorraine) has ever seen in (her) life" responds to the Pigman's call and makes an appearance, the Pigman leans "all the way over the guardrail, tossing peanuts" to him. He would hold up a peanut and ask, ""Bobo want a peanut?", and in response, Bobo "would show these monstrous teeth that (look) like dentures that don't quite fit, and the beast would grunt and swoon and move its head from side to side". Mr. Pignati would "toss peanuts right and left", and sometimes the baboon would "catch the peanut like a baseball". Apparently, Mr. Pignati and Bobo could continue this activity for quite awhile, and John and Lorraine, feeling like they "were intruding", soon become distracted and turn their attention to other exhibits. When John and Lorraine return, the Pigman has a fresh supply of peanuts and is still "chucking them over to Bobo". The baboon obviously loves the treats given to him by the Pigman, and Lorraine notes that when it is finally time to leave and Bobo realizes that he isn't going to get anymore peanuts, "you should have seen the expression on his face!" (Chapter 6).
yes he did feed him peanuts and half of hotdogs...
In the book it says that that Mr. Pignati feeds Bobo peanuts and hotdogs. I believe that he does fed him peanut and hotdogs, because it sounds like Mr. Pignati sees him every chance he gets to and he always feeds him. I would Mr. Pignati would know what he likes and doesn't like. In chapter eleven it says that Bobo like the peanuts in the yellow package not the ones in the package and he only eats a half of a hotdog.