We have been having such a battle with rats and mice this year! They have gotten into almost every one of our vehicles; and have figured out how to tunnel around our barn,and find spaces near the pole-building posts where there are gaps in the concrete that allow entry. We have been combating them with filling in the holes with rocks big enough that they can’t move them; and trapping, trapping, trapping. A little bit of poison, too. But I always worry about poison, both because we have pets, and we have so many raptors around. Hopefully soon we’ll get ahead of them again.
So, it was timely that our local Cattlemen’s Association hosted a rodent/pest expert at the March meeting. Dave Pehling, who many locals will know from the WSU Extension Office in Everett, is a veritable expert on rodent control. I thought I knew a lot about rodents; but I learned a lot of new things from his talk! Below are some random notes. He was such a fountain of information, I had trouble writing fast enough to keep up. I believe he could easily teach a 1/2 day class on this topic, an hour didn’t seem like nearly long enough. So, if you live nearby, and are ever looking for an engaging speaker on a heebie-jeebie, but important topic, keep him in mind!
· The best control of rodents is to remove food sources, but obviously this is sometimes impossible on a farm, e.g. where you have chicken feed out all the time for your birds, who need to be able to eat free-choice.
· Rats: at age of 3 months, they are fertile & ready to breed. They can have 1-12 litters per year (!)
· Norway rats are gray under tail, tail is shorter than the length of the body
· Roof rats are the other type we have here, becoming more common
· House mouse is the most common here
· Deer mouse has a bi-colored tail, they are the ones that carry Hantavirus (not any of the others). The photo he showed had a very wedge-shaped head, different from the cuter, classical face of the house mouse.
· Norway rats are good tunnelers; their poop has rounded ends, whereas roof rats have more pointed-end poop
· Norway rats will eat dog poop, so you have to keep it cleaned up if you want to eliminate them
· For mice, set traps every 5-10 feet, for rats, ever 15-20’. The home range of mice is typically 20’, rats 100’. Read: if you put traps on one side of a long building, you may be missing rodents that live on the other end!
· One idea is to affix bait to a trap with hot glue, so it’s hard/impossible for them to get it off. You can also screw traps to the sides of roof rafters, etc to catch them running on their overhead paths.
· Set the traps perpendicular to the direction of the apparent runway of the rodents- this is a bit counterintuitive. It works well to put several traps in a row, offset at random intervals. Then, when they are running, they won’t be able to adjust their cadence well enough to avoid tripping all of the traps- one will get them.
· Concerns over pets getting bait: one idea for a safe homemade bait station is to fashion a 4” x 18” long PVC pipe. Drill a hole in the center, use this to fish a wire through, which holds the bait in the center of the tube. Wrap the wire around the outside of the tube a few times to secure it. Then the rodents can easily go in the tube and dine, but even if your dog picks up the tube, he won’t be able to get the bait out of the inside.
· Legally, you must only use bait within 100’ of a building, and it must always be secured, so that wildlife etc. can’t get to it.
· Basic metal scouring pads work well for plugging holes- rodents don’t like to chew through metal
· If you have to make a barrier around a building, you can bury a “curtain wall”- an “L” shaped piece of metal that angles away from the building, so if they dig down below the wall, all they find is metal. Use sheet metal, not aluminum, as they can sometimes get through aluminum.
· Types of poison, these are the current three least hazardous:
o Warfarin- this is the anticoagulant one. The modern versions are persistent, so if your dog eats it, he may need vitamin K treatment for a full month to recover. It often takes 5-10 days to start exhibiting symptoms after ingesting.
o Bromethalin- a nerve poison (but don’t confuse this w/ the other “B-names” which sound similar). There is no antidote for this one, e.g. for pets, only supportive treatment, so be especially careful with this one.
o Cholecalciferol- excess of vitamin D3, this one is ok to use in organic environments. “Agrid3” brand.
o Second generation poisons are technically only legal for AG use- thus is why they are common on the shelves at farm supply stores; but theoretically, you can’t just use them in a residential/home situation, only for farms
Onto moles, which are not rodents, but a related control topic…
· Moles we have here: Pacific, Townsend’s, and the shrew.
· A single mole can make 200-400 mole hills/mounds.
· Voles are the culprits that eat root crops, they are vegetarians. We often call these little brown, stubby-nosed fatties “field mice”. Moles are insectivores and eat mostly bugs & worms, so are not to blame for killing plants/crops (other than the potential disruption they cause from digging and burying grass w/ mounds).
· Usually one mole has a territory of 0.5 – 6 acres. They guard their territory from other moles. They move around, “rotating” their own crops. So this is why people so often believe in wives’ tales on how to get rid of them. They try something ridiculous, and the mole seems to have gone away, so they assume it worked. But, really, he probably had just moved onto his next section all on his own!
· You can almost always find a mole tunnel following a fenceline- they like that area because it never gets trampled/collapsed by livestock or vehicle traffic. So, if you probe there, usually you will find a tunnel.
· If you collapse their mounds, they’ll just keep making new ones. But rather, if you gently rake the mound flat, preserving the tunnel below, the mole will eventually stop making so many new mounds.
· Trapping is the only effective method of eliminating moles. It is very difficult to get them to eat a poison. In our state, body-gripping traps are illegal to use (perfectly legal to sell, however); though the law is not really enforced anywhere.
· If you were to theoretically set a trap: probe near a mound to figure out where the tunnel runs. Dig a “skylight” in the top of the tunnel and wait a day or two, if it’s an active run, they’ll plug the skylight again. They you know they are using that run, and you can set a trap in it.