The couple decided to name the pair Dolly and Janis and were drawn to one because she was “chunky“.
Unbeknown to them, or anyone at the store, Dolly was actually carrying pups.
Megan and Daisy couldn’t believe their eyes when they woke up yesterday morning to find the rodents in their cage as usual surrounded by baby rats.
Dolly was still in the middle of giving birth to some of her offspring when the Scots pair walked in.
She went on to deliver 13 pups but ended up eating three of them.
This is common for rats that breed for the first time as they can panic seeing their babies and confused them as foreign bodies.
The couple from Hamilton, South Lanarkshire were delighted that in the end they managed to get 12 rats instead of two and plan to keep them all together.
Megan posted about the incident on Twitter last night, writing: “Me and my Mrs got two baby rats at the weekend from pets at home.
“We woke up this morning to 13 other baby rats.
“Feel like we’ve won the lottery.”
Adult female rats produce an average of 40 babies per year.
They can breed throughout the year in favourable conditions and are able to conceive within 48 hours of giving birth.
Speaking today, Megan said: “Me and my partner bought two baby rats on Saturday, Dolly and Janis.
“We picked Dolly because she was a bit chunkier than others but then we woke up on Tuesday and found Dolly giving birth.
“In total she birthed 13 rats but she ate three of them due to health complications.
“Me and my partner were completely in awe.
“We are hopefully going to raise them together as a family.
“I feel like animals but especially rats don’t get the chance to grow up in a family.
“Mama Dolly is keeping well.
“I’ve had to put Janis into another cage right now for a few weeks just for safety precautions.
“What has probably happened is that Dolly became pregnant from another rat in her litter.
“Luckily when I rang pets at home they gave me a free cage and offered to take the babies but me and my partner insisted on keeping them.”
Rats begin breeding as soon as five weeks of age and continue until about age two.
Females are fertile approximately every three weeks and during this time they have been known to mate up to 500 times in six hours.