Snipers deployed in war on giant 'mutant rats' Under siege ... Tehran's "mutant rats" are the size of cats and now outnumber the city's human population. TEHRAN has deployed snipers to fight an invasion of hyper-evolved "mutant rats," which officials say grew freakishly big after being exposed to radiation and chemicals. The cat-sized rats now outnumber humans in the Iranian capital. City official and university professor Ismail Kahram said the physically changes in the rats would normally have taken "millions of years of evolution," according to io9.com. The rat problem is not new to Tehran but with poison losing its effectiveness, the city decided to take its fight against the rats to a new level. It started sending out specially-trained marksmen at night to shoot the rodents. "It has become a 24/7 war," the head of the environment agency, Mohammad Hadi Heydarzadeh reportedly told Qudsonline.ir. We use chemical poisons to kill the rats during the day and the snipers at night. An initial deployment of 10 sniper squads was quickly boosted to 40, with the gunmen using infra-red sights to kill the rats.