Figtree's Walter Duran is set to fight for his dog's reputation by appealing a Wollongong City Council decision to categorise him a dangerous dog.

"He did wrong but it wasn't serious enough to put him in a muzzle - that would kill him," Mr Duran said.

He pleaded guilty in Wollongong Local Court yesterday to being an owner of a dog which attacked another animal.

It was alleged Sumo on April 24 this year got out of his yard and attacked and killed a chicken in the yard in Mary Ave, Figtree.

The chicken owner restrained the dog to a tree until Mr Duran arrived, the court heard.

Since the attack, Sumo has been declared a dangerous dog, which imposes a number of conditions on ownership, including the need to muzzle the dog in public and house the dog in a metal enclosure in the back yard.

Magistrate Paul Johnson fined Mr Duran $100 considerably less than the $550 local government fine.

Mr Duran was happy with the result but still wants to appeal the dangerous dog classification.

"I admitted in court that Sumo did the deed, but he has never touched a human and gets on great with kids," Mr Duran said.

"I think the classification is an over-reaction.

"When I found Sumo after the attack he was tied to a tree looking very forlorn like a naughty child.

"But he's a dog and nine out of 10 dogs would munch a chicken," he said.

The court heard Sumo had a record of wandering over the past five years, with four incidents.

"Whenever he gets out it has been my mistake, but he is a beautiful dog and most people love him," Mr Duran said.