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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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Dr. David Baker Seems To Be Mistaken
By mindless1 on 3/5/2013 10:12:29 PM , Rating: 0
Dr. Baker seems oblivious to biology as it effects evolution. You can't keep crossing early hominins and end up with anything other than an early hominin (or however far back you'd like to go) rather than what we are today, EXCEPT for mutations.

Take the largest rat on earth, cross it with a smaller rat, and you can't end up with an even larger rat with the same environmental conditions.

Granted the conditions might vary some, so one generation might be a little larger or smaller due to factors that stunt growth but overall the genetics that determine size remain the same UNLESS there is mutation.

They can't keep getting successively larger in an otherwise same environment without this, and actually, even in an otherwise same environment that environment itself could be causing mutations.

How about the poisons they're using, or radiation, or dare I suggest an enemy of state could genetically alter and release this pest? We aren't too far away from this latter possibility and how insidious it would be until these creatures reach a sustainable population level as predators.

What Dr. Baker seems to be doing is selectively ignoring that positive traits may come about by mutation, then of course the only remaining conclusion could be that mutation can only be negative... but it's merely because of a failure to recognize that mutation can cause positive attributes. Certainly it happens less often but when it does, *naturally* (pun intended) those with this trait will have a higher chance of domination.

... or not, you tell me? If you keep breeding two cave(people), what accounts for the change? Eating lots of Cheerios when you're a baby? I don't think so.

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?

RE: Dr. David Baker Seems To Be Mistaken
By invidious on 3/6/2013 9:45:36 AM , Rating: 2
Far more likely that this breed of rat is roughly the same size that it has always been. The reports of increased size can probably be contributed to poor data collection, incorrect correlation to a different breed or rat, or intentional sensationalism.

RE: Dr. David Baker Seems To Be Mistaken
By nafhan on 3/6/2013 12:25:57 PM , Rating: 2
OR the rats might have an excellent food supply while they are growing that's not typical of this breed in other locations/"the wild".

I know in humans, change in diet (i.e. more calories and especially protein) has been linked to increases in average height in countries from Japan to Holland over the past 50-100 years.

By superflex on 3/11/2013 10:01:21 AM , Rating: 2
Excellent food supply in Iran is an oxymoron.

RE: Dr. David Baker Seems To Be Mistaken
By Mr Perfect on 3/6/2013 12:27:37 PM , Rating: 2
Size could also be affected by the success of larger rats vs smaller rats. If Iran started with a normal population of rats and the largest rats lived longer and produced more children then the smaller rats, the Iranian rat population would start getting larger. Give it enough generations and you'd end up with rodents of an unusual size. So yes, populations can change even if they're not mutating.

RE: Dr. David Baker Seems To Be Mistaken
By JediJeb on 3/6/2013 3:20:32 PM , Rating: 2
Give it enough generations and you'd end up with rodents of an unusual size.

That's inconceivable!

By sorry dog on 3/7/2013 10:51:05 AM , Rating: 2
I do not think that word means what you think it means.

By mindless1 on 3/7/2013 2:38:56 PM , Rating: 2
You would not end up with rats larger than the largest breeder, any subsequent DNA would produce offspring that size or smaller, EXCEPT if there is a mutation which leads back to what I wrote in the first place.

Yes an entire colony could be roughly the size of the ancestor whose DNA they share, but not significantly larger than that over the span of only a dozen or two years.

Not sure how there are people out there that don't understand this, it's not an especially advanced topic. People and other animals haven't grown to twice their prior size over a few generations, including cases where there was an abundance of food (unless you count obesity, only an increase in waist size which isn't the case with the Iranian rats) there's a genetic difference.

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