Almost 40 snakes have been stolen, including eight pregnant females.
Merseyside Police are appealing for information after the non-venomous Royal Python snakes - which need specialist care and can grow to around 5ft in length - were stolen from an address in St Helens.
Thieves forced entry to the flat on Greenfield Road last Monday evening and took a total of 38 snakes, including eight pregnant females and 11 young snakes.
Two men were seen leaving the premises with two sacks before making off in a dark coloured vehicle.
Police said the Royal Pythons are non-venomous and extremely unlikely to pose any threat to the public.
Officers believe they will be offered for sale to people who are experienced in the handling of snakes locally or via the internet, and that the snakes are unlikely to come into contact with the general public.
Detective Constable Neil Henry, from St Helens CID, said: "This is a large collection of snakes that the victim had been gathering for a while. Clearly, there is a specialised market for such snakes and we would appeal to anyone involved in the buying and selling of snakes to look out for any Royal Pythons that they may be offered and consider whether they may have come from this address.
"These snakes, in particular the pregnant and young snakes, need specialist care and can grow to around 5ft in length. We are appealing for any help the public can give us to trace them.
"I would urge local people to cast their minds back to the evening of Monday, 16 March in case they saw the two males in a dark-coloured vehicle or remember seeing or hearing anything suspicious."
Anyone with information that could assist the police is asked to contact St Helens CID on 0151 777 6843 or Crimestoppers, anonymously, on 0800 555 111.