Although Tehran has had a decades-long struggle with rats, its rodent problem seems to have grown to epic proportions as of late. Giant rats that have been flushed out of their nests by melting snow are the focus of a renewed extermination effort in the Iranian capital, according to several reports.
Some of the rodents reportedly weigh as much as 11 pounds.
The International Business Times quoted Tehran city council environment adviser Ismail Kahram, who told Iranian news website Qudsonline.ir that the rats "seem to have had a genetic mutation, probably as a result of radiations and the chemical used on them."
"They are now bigger and look different. These are changes that normally take millions of years of evolution. They have jumped from 60 grams to five kilos, and cats are now smaller than them," Kahram said, according to the outlet.
The Huffington Post reached out to several rat experts to assess the validity of Kahram's claim. Dr. David Baker, laboratory animal veterinarian at LSU, told HuffPost that it's unlikely the rats got super-sized as the result of a mutation.
"Nearly all genetic mutations identified across the field of biology are harmful and confer a disadvantage to the species rather than an advantage. It’s not like in the sci-fi movies," Baker said in an email.
However, he pointed out that there are several species of "giant" rats found around the world that can achieve the sizes described by Kahram. Because their growth plates don't fuse after puberty, Baker explained, even common black rats can get very large.