what i'm worried about is other dogs attacking oliver!! monty is unneutered, and is VERY mellow and VERY friendly. he has been attacked SO many times the earliest bad one was when he was 4 months old, and it wasn't his fault (aggressive border collie attacked him - owner just watched as his dog walked up to monty, not telling us that his dog didnt like other dogs on the lead (which monty was) until AFTER we had pulled the dog off poor, yelping monty

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i am pretty sure that were monty neutered, he would not be the target for so many attacks.
also, bear in mind that i live in the UK, and where i walk my dog is a big, open park with LOTS of space, fields, trees, bushes..... i'm just thinking if you take oliver to a dog park, it's a more confined space, therefore more chance of a touchy encounter from another dog.
if i were you, i would take him to the park, watch how the other dogs behave first...if any of them look overly dominant then it might not be wise to let him off. or maybe you could ask the other owners there how their dogs gets on with full males???
i know it's a bit of a job to do that every time you take him to the dog park, but it's one of those things you just have to get used to unless you decide to get him fixed. (we aren't because we're hopefully going to breed him!!!

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sorry for long post there!!!