Coronavirus: Zoos reopen with 'unprecedented' ticket demand
Major zoo attractions say there has been "unprecedented" demand following the easing of lockdown restrictions.
Chester Zoo and Knowsley Safari Park confirmed they had sold out until July after it was announced that all outdoor attractions could reopen.
Both venues opened their gates earlier with visitor numbers limited and strict social distancing measures in place.
Chester Zoo chief executive Mark Pilgrim said attractions had a "responsibility to get it right".
Visitor numbers at the 128-acre Cheshire site are currently limited to 3,000 capacity, compared with admissions of 20,000 on a busy day.
A crowdfunding page for the Chester site raised £2.5m after zoo officials warned the pandemic could leave it facing a year-end debt of £24m.
Chief executive Mark Pilgrim said the zoo would start to open "very slowly".
He said: "We've been given the responsibility to open, so it is our responsibility to get it right."
Meanwhile, Knowsley Safari Park bosses said the team was "so excited" to open, after reporting a loss of £3m.
Car numbers have been limited to 400 per day, half what the park would usually expect.
The attraction has installed protective screens at the entry kiosks and coronavirus signage in the park and on the roads around it.
Managing director Edward Perry said the site had opened "gently, carefully and safely", but the zoo "still feels empty".
"I am determined to find the silver lining in all of this," he added.
In Lancashire, Blackpool Zoo said it was to remain closed.
A spokesman said staff were "doubling efforts" to open before July.