This page deals mainly with residential rodent control, for commercial rodent control please follow this link
Rodent baits are toxic. They should be handled with care. They should never be put anywhere pets or children could get into them. 'Could' covers those things you never intend, might seem like a nightmare, happen to other people, etc... It means they should always be placed in tamper proof, child and pet resistant class 1 rodent control stations.
(J.T. Eaton Strongbox Galvanized Steel Tamper-Resistant Bait Station (Item #910TP) when anchored to a concrete block or Bell Labs EVO Express with included anchor.)
Thousands of pets are poisoned every year, by homeowners putting out rodent poison in an area, or in a manner, that allowed their dogs or cats to get into the bait.
I am also, constantly amazed at the number of people who buy packets of some over the counter bait and throw it, out in the open, where anything could come by and eat it, birds, pets, wild animals and even children.
We put out bait in Class 1, pet and child resistant bait stations, that lock, that hold the bait blocks firmly on retention bars, and that are either attached to or contain concrete blocks to reduce the chance of pets or small children from moving them. We only place enough bait to kill up to four rats at a time, and never enough to poison a pet or child, and we prefer to place these stations outside of play yards or dog yards, putting them instead in side yards or out of the way areas to further reduce even the appearance of putting anyone at risk.
The biggest advantage of rodent baits is that they have a delayed reaction. Rodents don't even start feeling ill for a few days, so rodents are much less likely to associate eating it with effects of the poison - unlike traps, where it's pretty obvious to the other rodents as to what happened.
Most rodent baits cause rodents to die of internal blood loss, as most rodent baits are blood thinners. This blood loss isn't painful, but it does make them very tired. It also does not drive them to water. Instead, what happens, is that rats, especially, need to drink about 10% of their body weight every night in water. So there comes a point where the very tired, very thirsty rats, either decide to lay down and take their last nap, under, over, or inside your home, or venture outside for their last sip of water.
This is why you sometimes see rats wandering around during the daytime. They are disoriented, and poisoned, and thirsty. Sometimes, they are caught by a dog or cat at this point. At this point they have digested and excreted most of the poison and pose little threat of secondary poisoning. However, raptor birds can eviscerate and consume lots of rodents in a very short time - which is another reason why more and more requirements as to how and where bait can be placed are being passed. Fortunately, professional residential service programs, when done right, using pet and child resistant stations, will harm not children, pets, or raptor birds, like hawks, and owls.
Which brings up the biggest disadvantage: Unlike rodent traps which catch the rats in specific areas, rodent bait does allow rodents to die in unintended areas. Most of the times, those areas will be in a sub area or attic. Most of the time, they can be found if they die in those areas. In about 1 out of about 20 times, they will die somewhere, where they cannot be found - and they will cause a really bad, nasty odor. So we always recommend the following:
Mice can get through a hole the size of a dime, rats can get in through a gap of a half inch or a whole the size of a quarter. If rodents can get back in, they will.
If your home doesn't have rodents in it, exterior rodent control efforts can lower the exterior population by succesfully trapping or poisoning rodents which have never come in contact with those materials. Exterior rodent baiting programs have the most success, since baits work over several days, and rodents have a harder time figuring out what poisoned them. These programs can lower exterior activity - but will not eliminate all exterior activity.
If your home is not rodent proofed (or rodent excluded), you greatly increase your chances of having rodents move into your home that will not eat rodent baits, and / or that have seen traps in action and will avoid traps. Their offspring - will also be harder to catch or poison.
Rats, especially, can have food preferences. Rats raised on dog food, or easily accessible trash bin delights, may not eat any kind of bait.
On the other hand, if your home is rodent proofed, and you put out traps - you are much more likely to catch any rodents inside your home, as you will have limited their access to other food sources, and hungry rodents are much more likely to hazard a trap - even when they fear it.