Moby Rat

A pretty hefty roof rat in a picture send by Keller
ISD impressed me, but not so much the expert
from New York City.

I can tell you that fishermen aren't the only ones to exaggerate when it comes to biggest-catch stories. I've heard lots of tales. "I swear that cockroach that flew at me was 6 inches long!" "That rattlesnake was as big as my leg!" And, maybe most impressive, "The rats in our neighborhood are as big as cats!"

Nearly everyone and their brother's got a story about the biggest rat.  "Moby rats" they might be called.  Or "super rats".

A picture of one big roof rat sent recently by one our Texas school districts got me thinking.  What is a really big rat?  And what would it take to impress someone who has worked most of his life with rats?  Someone like Dr. Bobby Corrigan, the rat expert who consults on rodent control for New York City?

I decided I would send the school picture to Bobby and see what he thought.  He did not disappoint.  In his methodical way, he analyzed the image, and shot back a series of questions:

• "Is that a scrotal sack under the tail, or possibly enlarged female genitalia?  Hmmm...don't see any teats." [This blog post is going to get lots of strange Google hits]
• "Was the tail long enough to be pulled back over and beyond the head?" [Knowing what species is critical for the Guinness world record book--roof rat tails are generally longer than the body... otherwise it would be a Norway rat.]
• "How long was it dead?" "If it was dead for a few days in a ceiling," he explained, "...the body begins to decompose, the skin gets stretchy when held by the tail, and they can appear much larger than what they really are. Too, the body gases inside will begin to bloat the cavity and the whole end result is a very large-appearing rat." [Never thought of that!]
• Last but not least, he asked, "How much did it weigh?" [It takes more than a picture... you gotta have real data to impress a rat expert.]

Of course the upshot of all this was that I felt a little sheepish.  I should have thought to ask those questions before I even sent the picture. Duh! And who knew that you could rig a big rat competition by letting Fatty stew in his own juices a few days?

My last question to Bobby was, "What would it take to impress you?  What's a really big rat?"  

He answered quickly. "Any rat 2 pounds or over." "But it has to be fresh," he added.

According to Bobby, the heaviest live Rattus norvegicus on record is 1.8 lbs (29 oz) or about 820 g. Most “big boys” weigh in the 775 g range, he said.  And according to his book on rodent control, wild Norway rats over the years have been measured up to 19 inches.

By the way, compare these stats to what might be the world's fattest cat weighing in at 39 pounds. And an average healthy cat, I'm told, runs 8-12 pounds. No contest between rats and cats there. And chances of seeing a rat as big as a full grown cat is nil.

Of course Dr. Corrigan couldn't leave things gentlemanly.  He had to add, "Texans claims that everything is bigger in Texas.  You guys should own up to the bragging."

I'd say those are fighting words, Texas PMPs. So here's a challenge. The next time you find what you think might be an impressive rat, check the sex and species (lots of sites online for how to sex rats), weigh it, measure the length, and take a photo and send to me.  If you come up with anything approaching 1.5 lbs for a Norway Rat, or or 3/4 pound for a roof rat, I'll post  your catch on Insects in the City. And if it's a really big, record rat, and your office manager or spouse allows it, throw your double-bagged catch in the freezer--for proof. Bobby says he's waiting. Are we going to let him get away with that?