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  (Source: Mirage Studios)
"Mutant" rodents can grow to 5 kg, are about as big as cats, outnumber residents 6-to-1

According to a top government-owned English language newspaper in the United Arab Emirates -- The National -- the streets of Tehran have been running red with blood, as the government has deployed military troops to kill mutant rodents.

While Iran's Revolutionary Guard is typically more focused on hurling threats against its western adversaries, it's been forced to focus on the homeland amidst chaos in Tehran.  The city has been plagued by an insidious infestation of an unusual breed of rats, which reportedly grow to the size of a cat.  

Mohammad Hadi Heydarzadeh, the head of Tehran municipality's environmental agency told a state TV news agency last month, "It's become a 24/7 war.  We use chemical poisons to kill the rats during the day and the snipers at night."

So far 2,000 of the fearsome creatures have been killed.

The problem has become exacerbated as snow from the Alborz mountains seasonally melts, raising water levels and flushing the rats out of their subterranean lairs.  Researchers estimate the rats may outnumber their human adversaries six to one.  And these aren't your run-of-the-mill rodents.  Reportedly they grow to around 5 kg (11 lbs).

Iran wide
Iran has deployed skilled snipers to combat the rodent menace. [Image Source: ISNA]

Ismail Kahram, an environmental adviser to the city council, says the rats have changed in appearance over the years.  He comments, "They seem to have had a genetic mutation.  They are bigger now and look different. These are changes that normally take millions of years of evolution."

U.S. experts say this is unlikely, pointing out that even common black rats can get quite large.  Dr. David Baker, a laboratory animal veterinarian at LSU tells the Huffington Post, "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.  [But] during the Middle Ages, [standard] black rats in Europe reportedly grew large enough -- and children were small enough -- to carry off babies. Those had to have been some big rats."

Regardless of who is right, one thing is for sure -- these are some big rats.

Mutant Rats
One of Iran's massive "mutant" rats. [Image Source: Reuters]

The city uses tons of poison a year.  The special toxin used causes the rodents to become very thirst before death, a blessing as they then go off to die in the sewers, limiting the public health risk.  Still, it appears that the city is making little headway against the ever growing rodent threat.

Sources: The National (UAE), The Huffington Post



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RE: Dr. David Baker Seems To Be Mistaken
By jtemplin on 3/6/2013 12:20:39 AM , Rating: 3
Sounds like Tehran is claiming this evolution happened in the last 20 years or something. From early hominim to now is like 7 million years. So...not quite sure where you are going with that comparison.

Pretty sure Dr. Baker is just appealing to Occam's razor. Given the research on mutations which lets assume he is well-versed in (reasonable assumption I'd say) whats more likely: an invasive species from north africa, or just another species period, as another poster suggested or the infinitesimally small chance of a size enhancing mutation that occurred in an extraordinarily short period of time.


RE: Dr. David Baker Seems To Be Mistaken
By martin5000 on 3/6/2013 6:42:55 AM , Rating: 5
Yup, or an even more simple theory:

1) ALL rats can get fairly big, given the correct conditions and good food supply.

Combined with:

2) People exaggerate how big they really are, the rat in the image is well below the size of a cat. My cat weighs ~6kg and is much larger than that. I'd say that one is 2kg at most.


RE: Dr. David Baker Seems To Be Mistaken
By NellyFromMA on 3/6/2013 1:25:50 PM , Rating: 2
The article didn't say it was larger than an American obese cat.

That rat is definitely as large if not larger than an adult non-obese cat.


By martin5000 on 3/6/2013 2:55:33 PM , Rating: 3
It says 5kg. My cat is 6kg (he's big, not fat). My cat is way bigger than that rat, easily 3x the size.


By mindless1 on 3/7/2013 2:32:23 PM , Rating: 2
I have no doubt that they're referencing the size of the larger ones as justification for their measures to combat them, but at the same time I am fairly confident that someone managed to smuggle a scale into Iran once upon a time ago so they have a method of determining weight.

Yes all rats can get fairly big but except for starvation situations, which there wouldn't have been if the population had the environment to swell to such large numbers, an adult rat will grow to about the same genetically determinate size, they don't just keep getting larger and larger like filling a balloon with air.

It's a far more simple theory that rats that look different and are significantly larger, both of which were reported, aren't genetically the same.


By mindless1 on 3/7/2013 2:28:16 PM , Rating: 2
No, evolution is just one example. I also posed the more likely situation that it was the chemicals and radiation, which other news reports also support.

Occam's razor has nothing to do with it, he overgeneralized instead of looking at the specifics of the situation, that in fact these people have lived there thousands of years and happen to know what size rats there usually are. I know this is hard to believe, but in a rat infested place people tend to see one every now and then.

Yes it is highly possible they've cross bred, and today we, and they, have the tech to determine whether that is the case... and yet, so far they don't seem to think that is the situation.

There is nothing all that abstract or abnormal about a mutation that causes large size, becoming dominant quickly in a species that has a relatively short lifespan and frequent breeding. The abnormality would be what % of mutations cause the large size but given a sufficiently high population under extreme conditions, life still finds a way... rats will be around long after humans are gone no matter what mutation it takes for them to survive.


By tamalero on 3/12/2013 12:55:51 PM , Rating: 2
I think the point is.. what if; they didnt know these species well...until the snow started to melt and push them towards human settlements?


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