Callous thieves snatched three baby guinea pigs from their enclosure at a Sheffield farm popular with visiting families.
Shocked staff first noticed the trio had been taken from the pen they shared with parents Treacle and Henry at about 4pm yesterday at Manor Oaks Farm.
The babies are less than three-weeks-old and have not even been named yet as the farm is running a competition with pupils at nearby Emmaus Primary School to name them.
Concerned staff at the visitor attraction are now looking at stepping up security in the wake of the raid and are also temporarily restricting access to their animals.
Kate Hughes, an education and development officer at the farm, said: "We are really disappointed and concerned for their welfare as they have not been weened from their mother.
"Our caretaker noticed they weren't in their enclosure. It is the first time something like this has happened to us and it sadly looks as though a visitor may have taken them.
"We are shocked as the majority of our visitors are obviously very law abiding and just come for a nice day out."
The 32-year-old, of Meersbrook, added: "The farm area is very popular and we get more and more visitors every year. Young kids love seeing the guinea pigs so we want them back as soon as possible.
"As a precaution, we have decided that at the few times there is not a large staff presence in the farmyard some of the animals will have to stay in their enclosures until we improve the security."
She added that there is CCTV at the farm but not in the area the guinea pigs were stolen.
The farm has other animals including rabbits and goats and is part of the wider Sheffield Manor Lodge Estate, which includes the ruins of a Tudor-era house and cottages dating back to the Second World War.
Anyone with information about the guinea pigs' whereabouts should contact the Manor Lodge office on 0114 276 2828 or ring South Yorkshire Police on 101.