Dozens of frogs were found "hopping around" a supermarket car park after being dumped there inside a plastic bag, the RSPCA has said.
At least 50 of the amphibians were left outside a branch of Aldi in Finchley, north London.
Rescuers said they arrived to find a number of frogs had escaped the soil-filled bag and were roaming around the "completely hazardous environment".
The surviving frogs were released back into the wild.
RSPCA inspector Lauren Evans said two frogs died after being run over, but 48 were saved.
She said she arrived at the "dark car park" at about 21:30 GMT on Saturday to find it overrun with frogs.
"I had to run around scooping them all up with my hands and a bag before placing them into a secure tank," she said.
"Some were still in the plastic bag, which had clearly been tied up intentionally.
"They would not have been able to escape if there had not been the hole, but equally they would not have been able to breathe without it."
She said the animal charity had "no idea" where the frogs came from, nor why they were left inside a plastic bag in a car park.
"None of them would have survived if they had been left that way," she added.