Three female rats, one suffering from mites, were dumped at a communal bin area in Watson Street, Motherwell.
The Scottish SPCA was alerted on Monday by a member of the public after she found them in a large cage sitting in the corner of the bin shed.
The rats have now been nicknamed Cindy Lou, Betty Lou and Martha May by staff at the charity’s Lanarkshire centre where they are being kept.
Senior inspector Billy Linton appealed for information.
He said: “The rats are doing okay, and they don’t seem to have come to any harm, thankfully. The trio are now receiving some treatment for their skin after one of them has shown signs of mites.
“This is not only a cruel incident but it is also an offence. We are now looking to trace whoever is responsible and ask that anyone with information to get in touch.”
Abandoning an animal is an offence under the Animal Health and Welfare (Scotland) Act 2006. Anyone found guilty of doing so can expect to be banned from keeping animals for a fixed period or life.
Anyone with information is being urged to contact the Scottish SPCA animal helpline on 03000 999 999.