The opening of Graves Park animal farm was delayed last Saturday after an arson attack and slaughter of chickens.
Some chickens had broken necks and others had been killed by foxes in the park after being set free.
A chicken pen was still smouldering.
The attack came after reports of a group of youths in the park on Friday night – but it is not yet known if there is a connection.
David Hargate, council head of parks and public realm, said: “It is despicable that anyone could carry out such mindless vandalism and we will be cooperating with the police.”