I don't really have anything against rats[1]. But there are some places you really don't want them. Poisoning is often used, but unfortunately rats can sometimes develop resistance. Apparently, what happens is that rats eat just a tiny bit of any new food they come across. So they don't always get a lethal dose of poison. This makes them sick rather than dead, so that particular rat knows not to eat it again. Thus there is selection for increasing resistance to the poison.
I propose a strategy of first introducing a poison-mimic. This bait would look, smell, feel and taste essentially identical to the true poison formulation (to rats senses[2]), but non-toxic. The rats would thus become accustomed to this food. This might take a couple of weeks or so, and would need to be determined empirically. At which point you start putting down poison, and all the rats are killed.
[1] Oh, except that they once killed and partially ate my guinea-pigs. I'd forgotten that. Bastards.
[2] Humans could distinguish them by different text stamped into the pellets.-- Loris, Aug 10 2006 //Humans could distinguish them by different text stamped into the pellets.//Then they would learn to read. Then we would have some real problems!-- ldischler, Aug 10 2006 Rats eat warfarin just fine. The problem is evolution: rats have become immune to warfarin. This has prompted the invention of super warfarins. Similar to the antibiotics arms race.-- bungston, Aug 10 2006 I still haven't found any rats immune to my trusty, rusty shovel (by BUNGCO, of course).-- methinksnot, Aug 10 2006 If you have rats in your home, maybe you should start cleaning it more often... :-)
Also, why not just get a cat?-- runnerfajita, Aug 10 2006 //Rats eat warfarin just fine. The problem is evolution: rats have become immune to warfarin.//
Sigh. Bungston, I know. That is essentially the problem I'm attempting to solve.
The reason that resistance to warfarin has evolved is because rats tend not to eat much of any new thing, so some can survive the small dose. Think - if it killed every rat, the resistance wouldn't develop. So a few rats survive the initial small dose, never eat poison again. Then they go on to breed, producing a new population with slightly increased resistance. Repeat a few times and rats are unsusceptible.
Which is where the non-toxic starter pellets comes in. The objective is to administer a massive, guaranteed lethal dose, so resistance doesn't arise.
Incidentally, I didn't mention other Coumarins in favour of brevity, because few would know what they were. The actual poison used would simply be a rat-poison; it wouldn't have to be actual warfarin.-- Loris, Aug 11 2006 I actually like this idea. The "starter warfarin" doesn't have to have warfarin at all, just something that tastes and smells like it (vanilla?).-- Spacecoyote, Nov 11 2008 2 years pass and I never came back here. The great thing about warfarin as a poison is that the rats do not feel sick. Having very thin blood does not make a rat or a person feel bad. Bleeding does not hurt too much either. I think rats eat warfarin up - those new to the bait or those who have eaten before. No "never eat poison again". This as opposed to something like arsenic, or strychnine which do make rats or people feel very sick.-- bungston, Nov 12 2008 2 years pass and I never came back here. The great thing about warfarin as a poison is that the rats do not feel sick. Having very thin blood does not make a rat or a person feel bad. Bleeding does not hurt too much either. I think rats eat warfarin up - those new to the bait or those who have eaten before. No "never eat poison again". This as opposed to something like arsenic, or strychnine which do make rats or people feel very sick.-- bungston, Nov 12 2008 random, halfbakery