The RSPAC is appealing for information after a small black snake was found on the front patio of a house in First Lane, Hessle in Hull.
The short flat-headed wolf snake is around 18 inches long with a body approximately the width of a finger.
RSPCA Inspector Natalie Hill said: "An eagle-eyed dog-walker spotted the dark snake against the light background of a patio at the front of a home in Hessle and was able to contain it in a plastic box.
"When he and his wife did some research, they realised this was not a native snake, so they called the RSPCA for help.
"This poor little snake is most likely a stray pet - snakes are excellent escape artists, so if anyone has any information, we would appreciate it if they could call us on the RSPCA Appeals Line on 0300 123 8018."
The reptile is currently living with a specialist carer and will be rehomed if the owner is not found.
Many of the snakes the RSPCA’s officers are called to collect are thought to be escaped pets. The animal charity recommends for owners to invest in a suitable enclosure and consider having snakes microchipped by a vet.
Reptiles, particularly snakes, will take the opportunity of a gap in an enclosure door, or a loose-fitting lid to escape.
The RSPCA advises anyone who finds a snake they believe is non-native to keep a safe distance and contact the charity by calling 0300 1234 999.