Several people have raised fears of secondary poisoning from rodenticides.
The old, infamous rat bait, 1080, produced rodent carcasses that were quite
lethal to any creature that fed on them. Modern rodenticides do not produce
rodents with highly toxic flesh. However, if an animal eats a whole rodent
with a stomach full of bait, they could experience toxicity.

By far, the greatest danger is direct consumption of bait by pets or
non-target animals and that is why bait must be in a secure location. The
best baits contain Bitrex, which tastes very bitter and discourages feeding
by non-target animals.

In my experience with the rodenticides we use, rodents usually return to
their nest to die. We rarely find them dead where non-targets can get them.
However, to reduce the risk, you should trap intensively first and catch as
many as you can, then bait to get the remaining few. This reduces the risk
of one dying in a wall or ceiling also. Some rats are virtually impossible
to trap, while mice are usually quite easy to trap. Glue boards tend to
catch only juveniles and are not nearly as effective as snap traps. I like
chunky peanut butter as a snap trap bait. Rodents are thigmotactic (stay
against walls or other surfaces) and traps should be set at a 90 degree angle
against walls so they run over the trigger as they travel along walls.

Some complained that baits are ineffective. Most baiting problems are
related to food competition. You put out bird seed, pet food and squirrel
food, have compost heaps, nut and fruit trees and they don't eat your bait?
Try removing alternative food sources before baiting. I know you hate to
stop feeding birds, but if you clean everything up for only a few days, you
will be amazed at how much better they take the bait.

The worst scenario is - you never reduce harborage, rodents have access to
your crawlspace, attic, under your garden shed and you only bait when the
rodents get really bad. My firm performs 10 or more rodent control services
each week and a service I performed yesterday serves to illustrate this
problem.

I was called to consult on an odor problem in a dental office. It seems they
had been setting out D-con, because of a chronic rat problem. During the
recent hot spell an annoying odor problem in a lab became overwhelming.
Despite an extensive search they could not find the source. It took me about
2 minutes to locate the culprit, a large dead roof rat under a sink cabinet.

I inspected the perimeter of the building, which they thought they had
rodent-proofed long ago. I discovered a wide open crawlspace vent hidden
behind a shrub. I also found a large hole gnawed thru the crawlspace access
door, a vent screen that had been pushed out, and burrows under the
foundation. Further inspection revealed a large, enclosed bird feeding area
that looked like a rat factory. Burrows and droppings were everywhere, so
was bird seed. They had no idea the scope of the problem and needless to
say, they were quite cooperative.

We trap first, then bait to cleanup the remainder. Finally, we have them
seal all the rodent accesses. We also will maintain bait stations near the
bird feeders to prevent future population build up.

Finally, tin cats catch only mice for which they work very well. However,
snap traps are much cheaper. Unfortunately, most bird feeder problems are
from rats and they have a much larger home range (10' for mice Vs 100 yards
for rats) and can be a problem for your neighbors as well. Studies have
shown a good cat will lower rodent population, but not eradicate them. In my
opinion, bobcat urine would work about as well as an owl decoy works as a
scarecrow. Rodents are quite intelligent, and soon figure out, the predators
are not around.

There many myths and misconceptions about rodents and my comments only
address and few of them. A consultant and former Purdue University
Professor, Dr. Bobbie Corrigan, has been studying rodents for 30 years. He
is a regular speaker at out Washington State Pest Control Association
educational seminars and much of what I do is a result of his field research.
I'd urge you to base your rodent control decisions on science and not
folklore.

Terry Whitworth