Rats are actually new to the US continent. Late 1700s, I think. Since I have a little farm, I have rats – and because I am a contributor to the general pool of knowledge of rat (and other animals) vision, I can speak to what they see and how to hunt or trap them.
In passing, I’ll mention that the most exotic vision on earth probably belongs to the Harlequin shrimp. It can see everything you can see just as well as you can, plus eight colors you can’t even imagine, in wavelengths you only read about, and it can simultaneously filter and polarize light two different ways in different eyes across all of these wavelengths. It can hit you so hard it will break your finger if you piss it off. If your butt-ugly little niece sticks her gob up next to the glass of a standard glass aquarium in which one lives, it will run over and hit the glass so hard it will shatter.
Back to rats. First, the bad news. The bad news is that there isn’t any good news about rats. You are not going to get rid of rats unless you completely eliminate their food supply, and that won’t happen anywhere people live year-round. Rats are prolific and almost everything you read about them is wrong. I assume you read textbooks about rats…doesn’t everyone? Or am I the…
OK, so male rats have sex between 20 and 50 times in any 6-8 hour waking period (they aren’t particular whether it’s with a female or another male) and females can throw 20 pups a month, but average 6 or 8. If you live in a major metropolitan area, you are probably within ten feet of at least two male rats having sex. Females can give birth once a month (22-24 days, actually) and they breed again 18 hours after they have given birth. Something is always in the oven.
The most common rat in the world used to be the grey rat, Rattus Rattus, which actually comes in several colors and two-tones and can have beautiful pelts. But they have generally been displaced by Brown rats, Rattus Norvegicus which are much bigger and much more aggressive – and mis-named since they came to the west from Denmark, not Norway. Whatever. They are sometimes called ‘wharf rats’. They can reach 24″ stem to stern and weigh over a kilo.
Packs of rats have attacked people and killed infants. New York is notable for rat attacks. It was about dusk in Manhattan one day in 1978. A lady left work and was walking to her car as a pack of rats came out of an alley. Hundreds of them. They crossed paths. The lady started screaming and dancing and it scared the poor rats which immediately tried to escape by running up her legs under her dress. When they couldn’t get out, they started nibbling her bums in fright. The lady became much more animated and a LOT louder, and some spectators came to try and frighten the rats off, but the rats started after them, so it seemed to them, and they ran away to call the police. By this time the lady had made it to her car and as she jumped in, the rats evaded her crushing thighs and escaped, some to the pavement and some to her car hood. She raced away gesticulating wildly, rats still running around on, and maybe in, her car. When the police got there, she was gone, but the rats were still in the street. The police wisely stayed in their car. True story.
In another famous New York incident, a lady heard her 3 month old baby screaming. She thought it was hungry. Nope. Rats were eating it. They didn’t eat all of it, but they ate enough to kill it.
In another incident, a night watchman heard a noise and shined (or is it ‘shone’?) his light under a pier. A large eel had crawled partially out of the Hudson river and was stalking a rat. The rat apparently saw the eel about the same time and they both decided the other was dinner. According to the watchman it was a battle of epic proportions but it ended in a tie when the eel couldn’t drag the rat into the water and the rat couldn’t drag the eel all the way out. They split up and retreated to their own provenances, both the worse for wear.
Pure white rats, including pet rats and lab rats, are an albino variant typically bred from an original French albino Rattus rattus. Albino rats appear in nature, but usually don’t survive long in the wild because the albino trait includes a less sensitive sense of smell and ~20/1200 vision instead of the ~20/600 common to most rats.
Rats are dichromats plus. Their eyes are placed on the side of their head, so they have a huge field of vision, but only about a 76 degree binocular overlap compared to about 105 degrees in humans. Their field is bigger, but our depth perception is much better. Rats use both relative and, to a lesser extent, absolute motion parallax to improve their depth perception. You have probably never seen a rat with it’s eyes closed, but rats have upper and lower eyelids and a nicitating membrane which we don’t have anymore. They have a huge field of vision, but they can’t see very well. Rats distinguish bright from dim more readily than color. They can see UV and subdued shades of blue and green against shades of grey. Some of us postulate that when rats used to weigh in around a hundred pounds and spent more time in the light, they began to evolve color cones but the K/T boundary extinction event made it unnecessary.
I’m going to skip the technical bits and say simply that visual acuity is measured in cycles per degree (cpd). In humans it’s about 30. In normal rats the cpd is about 1. A normal, unaided human eye focuses from ~90.5 inches to infinity. A normal rat focuses from ~2.7 inches to infinity. That means that a rat’s visual acuity is basically fixed at 20/600 and can’t be made better. Human eyes can be corrected by diopter changes as small as .3 but a rat would need a 14 diopter change to even notice, and that would make it’s vision even blurrier.
There are veterinary texts dedicated to rat eye issues. When someone brings their pet rat to me – usually because they think it has rat-lung disease, which it doesn’t – I find it’s always much easier if I sedate it underwater for about fifteen minutes first and then soak it in bleach. Slugs and snails get the bleach treatment too, and all local vegetables are dipped in a light bleach solution and inspected for slugs. Sometimes people bring their rat for an x-ray. My x-ray machine is trade-named ‘Rat Zapper’. I put a piece of film in the top and throw the rat in. The film rarely comes out – or the rat – but we are able to console our clients that our $299.99 celebration of life service followed by being hermetically sealed in rat paradise, a piece of capped sewer pipe followed by everlasting peace for their beloved pet in a real rat den filled by trained mourning rats is the perfect final resting place – and is half price this week. We hold a brief, open sewer pipe service for the mourners. When they leave, we stuff the body with rat poison and toss it over the fence just like a regular human funeral home and sterilize the sewer pipe.
If you see a rat during the daytime, you are infested. Rats try to be nocturnal because bright light hurts their little ratty eyes, but they will come out in the daytime if there isn’t enough food for the population. Apart from eating, evacuating, screwing and eating more, rats do two things obsessively. They chew and they dig. They can become so obsessed with digging tunnels that they have been observed to dig until they drop dead of exhaustion. Invariably, that occurs when they are trapped in some laboratory waiting for a bumblethumb student to practice drilling holes in their skulls.
Rats are born with white teeth, but their uppers have generally turned yellow by 25 days with the lowers following soon thereafter. Mice are similar. I picked up a cute, teeny-tiny baby mouse once. It had fur and it’s eyes had just opened, so it was about a two week old Mus musculus, or common house mouse. It had beautiful white teeth. It didn’t run – I just reached down and picked it up. It was sooooo cute! Then it bit the living shit out of me and I stomped it into rat paste.
Rats have tiny bladders and urinate almost constantly. Their urine glows under black light so they can see it, naturally, but you can use it to track them. They typically follow the same trail night after night. Rats can’t see the color red. Even bright red lights look like dark spots to them unless the lights generate heat in the UV spectrum. If you want to hunt rats, red lights or night vision scopes work nicely – except that most night vision scopes have IR lights on them to increase their range and brightness. I haven’t seen any testing for IR vision in rats so I can’t comment, but I can’t afford a thermal imaging riflescope. So it’s a red light and a pellet gun for me.
If you merely want rats to move to a new home, you can mess with their tunnels. I have poured tens of pounds of marbles down ratholes; concrete; bags of pool salt; sand; diatomaceous earth; expanding foam….I have run 130 db airhorns in their holes for ten minutes. I have blown a pound of gunpowder down the hole, followed it with five minutes of propane, and set it off. I have set non-explosive IEDs with red laser triggers. I have poured in several pounds of crushed pool chlorine followed by liquid chlorine, which creates chlorine gas, and then sealed the hole from one end. I have tried gasoline. I have fired 12 ga. shotgun blanks down the holes to try and blow out their little rat eardrums. I have used 5 watt lasers to try and burn off their beady little eyes. I haven’t tried a commercial high-pressure/high volume steam cleaner because I have never seen one here.
I have spent days with 30′ waterproof lighted borescopes fishing a thin piece of flexible wire through a rat den and then used the small wire to fish through a braided copper wire connected mechanically but not electrically every foot to a solid copper ground wire and a heavy aluminum wire. I won’t tell you how completely improbable completing it actually was. Then I grounded the braided brass to a brass rod pounded ten feet into the ground in the center of a 10,000 gallon above ground pool. It transverses the entire tunnel complex and is fed up about 150′ to a lightning rod in someone’s albizia tree. I am awaiting a serious lightning storm. I hope to create a permanent splattered metal casting of an entire rat cave complex and have enough power left over to animate the Frankenstein monster hidden in the neighbor’s outdoor smokehouse. Really – what could possibly go wrong?
Rats are pretty smart. They avoid snap traps. Older ones avoid cage traps after they see another rat trapped in one, but I can’t resist using physical traps because I want to come out and find their little skulls crushed in a trap I set. It rarely works. If a rat finds a dead rat in a trap, it smells the trap and the bait and will avoid similar traps in the future unless you sterilize the trap and change bait.
Rats won’t eat anything new until they have smelled it a couple of times and tasted it once or twice. They can’t throw up, so they take small tastes two or three days in a row. If they don’t get sick, they will come back and gobble it up about the third time. Rats compete for food, though. If mama comes back and has cheese on her breath, every rat she passes will get a whiff and will then go find it and eat all they can get of that particular cheese immediately.
About the only thing that works reliably over time are bait stations with slow-acting rodenticide. The rats eat some and don’t get sick. They go home, the other rats smell the bait, follow the trail to the bait station and eat – and don’t get sick. In a few days they all gorge on it and drop dead – but they don’t die near the bait station, so they don’t associate it as a bad thing. You just have to keep the bait station full and remove the dead rats from the area before Fluffy eats them – or Fluffy is a goner too.
“I have a basement full of rats! I’ll get a big cat and throw it down there. Or a rat terrier.” Do that. In a couple days, you can go down and clean up all the bones and fur. The rats will have eaten it. And they are watching and waiting for another one. Even a big one…like you.
New York has a Rat Department staffed by people who do nothing but catch rats their entire career. They catch thousands of rats, but they didn’t manage to catch Hillary. Really, though, all they are doing is making room for more. Ten more are born for every one they catch. They are diligent, but they are a PR department. They are sent out to make waves wherever there is a large rat breakout so the Mayor can give speeches about once again beating the horrid rat menace. Everyone knows it’s bullshit.
It bothers me that people use ‘humane catch-and-release’ rat traps. They catch the goddamn disease-ridden vermin and their plague-carrying fleas from their house and release them at the neighbor’s house. If the neighbor catches you doing it don’t be surprised if they open the trap and pour the rats down your pants. And then beat at them with flyswatters until they go mad. You won’t do it again. I know. I did it once with a bag of rattlesnakes and turned them in at a capture station. It was assholes and elbows when they opened the bag.