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How Cities Are Using Dry Ice To Kill Rats (usatoday.com)
Some of the United States' biggest cities have resorted to using dry ice to kill rats. Since dry ice (frozen carbon dioxide) turns into a gas, sanitation officials simply need to drop chunks of it into rat infested burrows and let science do the rest. Longtime Slashdot reader mi writes: USA Today reports: "Earlier this week, USA TODAY observed Chicago sanitation department workers at one of the city's oldest parks scoop chunks of smoking dry ice into a burrow before quickly covering the entry and exit holes with dirt and newspaper to stop any rats from escaping as the -109.3-degree Fahrenheit gas dissipated. Sanitation workers say they treat burrows during morning hours, when rats are less active and most likely to be huddled inside the burrows. The asphyxiated dead rats then decompose in place and out-of-sight of city denizens who count the disease-carrying vermin among the vilest of indignities of urban living. 'We are seeing 60% fewer burrows in areas where we are using the dry ice,' said Charles Williams, Chicago's streets and sanitation commissioner. 'It's more environmentally friendly, and it's very humane on the rodents as well.'" Humane or not, what is so especially "undignified" about rats? What makes them worse, than, for example, cats, deer or wild horses?
"Humane or not, what is so especially "undignified" about rats? What makes them worse, than, for example, cats, deer or wild horses?"
The author of the summary has obviously never had a rat infestation. They can swim, dig several feet down, chew through concrete, plastic, wood, drywall, and otherwise go to amazing destructive measures to get to a heat or food source. Unlike mice, keeping your food in the cupboard or Tupperware containers is useless as they chew right through them, and destroy your home's foundation while they are at it. No, rats are not at all like wild horses, cats, or deer. Rats are a special kind of hell.
If you need an ecological reason. The destructive urban rats are an invasive species, not native to North America. We brought them here - and I for one applaud every effort to get rid of them.
Actually asphyxiation by breathing near pure CO2 isn't bad. It's remarkably swift.
Likely better than thallium or anticoagulants like warfarin. There isn't a perfect way to kill rats, but this seems like an improvement.
I'm not sure why they are using dry ice rather than just a tank of compressed CO2.
Likely because the dry ice is cheaper, easier, and more effective. It also requires less equipment and training.
Or pure N2 for that matter
N2 is lighter than air, and you need enough of it to completely displace the air. CO2 is dense, and even denser when it is at -109F, so it will flow into the burrows. It is toxic at about 7%.
which eliminates the stress response entirely
I doubt if most people with a rat infestation consider this to be a critical criteria.
> Fleas.
No, rats. The fleas are just a vector to get it from rats to people. The fleas come with the rats.
I really do not think there is a solution that involves not killing them. If you stopped killing rats for 4 months there would literally be something like a hundred times as many rats as there were before. They would explode out of the sewers and eat small children and babies in their cribs. Their ability to reproduce exponentially would mean that every edible morsel of food in the area, whether human, pet, or more generic foodstuff, would necessarily be converted into more rats within a few years time.
Troll is not a replacement for I disagree.
During World War 2 when the Dutch were near starvation late in the Nazi occupation, my grandmother - a young woman at the time, obviously - heard her baby sister suddenly start screaming from her crib in the next room. She rushed in to discover a rat chewing on the baby's chest.
They're nasty, disease-carrying vermin, and anyone who feels sorry for them (or, idiotically, asks how they're worse than cats, deer, or wild horses) simply hasn't had a close encounter with them. I specifically keep cats around as nature's own anti-vermin patrol. My cats are well worth their value in purchased cat food and vet visits just for that function alone, and as a bonus, every once in a while they deign to permit me to pet them for a while.
Irony: Agile development has too much intertia to be abandoned now.
Although it's an old technology, older than the 3.5 mm audio jack even, the ordinary mousetrap is humane, effective, reusable, and available in multiple sizes. They kill instantly; you'll never find a mousetrap with a live rodent wiggling around in it.
The glue boards, on the other hand, are pretty gross. The rat sticks to them and then you toss the thing into the trash, which always struck me as somewhat psycho. Sometimes people buy them without it dawning on them they're going to end up throwing a live mammal into the garbage. I knew one guy who came across a starving mouse wiggling in the glue, was overcome by an unexpected burst of empathy, and spent the next half hour making a mess outside with rubbing alcohol trying to pry it off without tearing any limbs.
CO2 is toxic?
Yes. CO2 forms carbonic acid when it is dissolved in water, and acidifies the blood to lethal levels when above about 7%. With conditioning you can tolerate slightly higher levels.
No. You're talking MONOXIDE.
CO is much more toxic than CO2, but either can kill you.
CO2 only deprives the air of usual ratio of oxygen, and is not notice in itself.
No. This is wrong. If you add 7% CO2, you still have about 18% O2, which is more than enough for a healthy person. It is the CO2 that kills you, not the absence of oxygen.
Asphyxiation via C02 is an absolutely HORRIBLE way to die, regardless of the creature. There's a reason Carbogen (C02/Oxygen mix) is used to induce anxiety to test out anxiolytics. I mean I get that they need to solve the infestation problem but can't we choose a method that isn't also a completely inhumane method?
This is just not true. Low concentrations of CO2 can cause distress. High concentrations are fast and painless.
There have been lake and volcanic outgassing events which release massive amounts of CO2 and it kills people and animals where they stand, in seconds.
See the Lake Nyos incident to see how CO2 kills.
And here's the final report on the incident from the USGS (PDF): "In this incident, asphyxia resulted from the displacement of normal atmosphere (approximately 21 percent oxygen) by a cloud of carbon dioxide gas. Under such circumstances, victims will literally "drop in their tracks" after taking a few breaths and experience no feeling of suffocation. The actual mechanism of death is believed to be a paralysis of the respiratory centers in the brain by very high concentrations of carbon dioxide. Lethal levels of carbon dioxide are in the range of 8 to 10 percent (Sittig, 1985)." - pp. 18-19
Also: "Additionally, many victims were found in their beds still covered by bed clothing. Victims found outside appeared to have collapsed suddenly without substantial movement. Animals were described as "dead in their tracks" in herds rather than dispersed." - page 17
An accepted humane way to kill lab animals is with high concentrations of CO2. The key is "high concentrations."
This concept, of dry ice generating carbon dioxide which flows down into holes at high concentrations, is actually brilliant and humane.
Not directly, but they are the carrier for a very common parasite, T.gondii. It's endemic just about everywhere domestic cats can be found. It infects humans too, though it can't reproduce in them. In humans it concentrates in the brain, usually to symptoms so mild they go unnoticed - the victim just feels tired and slightly feverish for a short time - but the presence of the parasite has been linked to a number of mental health conditions.
T.gondii is notable for influencing host behavior - it causes rats to become less fearful, increasing the chance of getting caught by a cat and consumed so the parasite can continue it's life cycle in a cat. The same mechanism of altering brain chemistry that causes rats to become less fearful is also active when it infects humans, but as it evolved to mess with rat brains the effect on humans is different.
As a matter of public health, it would be wise to place restrictions on domestic cats - at the very least to deny them access to outdoors areas where they may have contact with wild animals. But cats are cute and everyone loves them, so such measures are politically non-viable.