Ground Squirrel Management
These are my notes from Farm Bureau’s presentation on California ground squirrel management, arranged by what I thought were good take aways for regular people (it was a course designed for professional farmers and pest controllers) — but everyone keeps asking. All of this information is available at this website.
Know your ground squirrels
Ground squirrels hibernate in the winter, and if it’s a hot region, they also estivate, aka, sleep lightly through peak summer.
When you first see ground squirrels emerge, those are the males, staking out their territory. Any effort you put into ground squirrel management should start two weeks after you see them because then the female ones are waking up.
Ground squirrels eat grasses the first part of the year and when they die out, then the squirrels eat seeds.
All of this is to say, know thy squirrel and plan accordingly. There is no singular way to manage them, and doing it in tandem with multiple methods will bring you the most success.
Habitat modification — step 1
If you have brush piles around, they will make their home there. The more open and exposed, the less they will move in. If you can, the best place to start is by ripping your field down 18″ — 12″ is too shallow. 18″ destroys the burrows and makes it less desirable.
Owl traps won’t work because squirrels are day animals and owls are night animals. Similarly, raptor attractants don’t work that well either (from experience, I’m sure the raptors enjoy the squirrels but it’s the coyotes that really do the work around my place).
Trapping — step 2
There’s two types of traps — kill style and humane ones, but the humane ones you have to euthanize the squirrels (and drowning is illegal in California, so it’s generally shoot them or create a carbon dioxide box).
For kill traps, they recommend the conibear 110. You put it at the entrance to the holes. DO NOT USE THIS IF YOU HAVE CONCERNS ABOUT DOMESTIC ANIMALS or children— it will kill/maim anything trying to get into the hole, like a cat. You can also use a tube-style trap, but you have to train them with pre-baiting that it’s okay to go into boxes, which can take a few weeks of you feeding cereal for no reason.
For humane traps — this is the one to use for domestic concerns — as if you catch something you don’t want, you can let it go. But you have to commit to killing what you catch. You can dispose of squirrels by double bagging and putting in trash or putting them in their burrow and covering it up.
Fumigation — step 3 — only in spring
This seemed like the most effective method all around — but, spoiler alert, you need to be certified to do most of what this outlines. It’s the most effective because it’s fast and you don’t have to stress non-targeted species getting killed during application or after squirrels die.
ALWAYS FOLLOW THE DIRECTIONS ON THE PACKAGING THE DEVICE COMES WITH
We fumigate in spring when the soil is moist and cracks are at a minimum. The idea is to seal as much of the gas underground as possible. Closing up all holes except the one you’re using to fumigate is best practice. It takes about 7 min to kill a colony in their burrow, but to be safe, people do it for like 15 min. Do not fumigate near buildings according to the manufacturer’s label (generally 50–100 feet away is ok).
There are aluminum phosphate tablets that are very effective but you need licensing and they are highly regulated, so probably better to hire someone.
Secondary effectiveness is with gas cartridges, but they only range in 60–80% efficacy. They are also more expensive, but not restricted by licensing.
There are exhaust machines that are quite effective, the one demoed for us by the county has an additive that creates a visual smoke so you can see cracks and seal them. This requires licensing.
People buy Rodenators but they are not that effective, surprisingly, and they are fire hazards.
Shooting — meh
So they mentioned shooting and I’ll remind you that lead’s illegal in California. Anyway, it’s not that effective unless you have a concentrated program and you get at least 70% of the squirrels or more. Be sure to clean carcasses.
Baiting — Step 4 — summer and fall (when the grasses are dead)
So baiting is the big one to worry about non-targeted species. Kids, cats, rabbits, livestock, etc can be harmed, so if you do this you need to do it carefully.
There are two types of bait, 1st gen and 2nd gen. The second generation bait is immediately effective but there’s no known antidote if you need it, and squirrels need to get pre-baited as described above because they don’t like the taste and can get smart to it. So I’m not going to talk about its application because it seemed like a nothingburger. If you do want to do 2nd gen, the biggest takeaway I had was that when you apply it, you only need like two or three bits of grain spread out really far — people dump it and it’s expensive, dangerous, and will result in huge fines.
1st gen bait has to be done right to be effective and safe, so here goes. You need to be licensed to get the good stuff, the widely available stuff is less effective.
You need to set up a bait station as described in the link above. It needs to be secured so that it doesn’t fall over and also set up so hands, cats, rabbits, kangaroo rats, etc, anything not targeted in your area, cannot get a paw or in there except squirrels. It also needs to be anchored to its spot so it can’t get dragged off or moved. They showed people putting wire fence around them that seemed like a really good idea.
There needs to be two applications of bait over 4–5 days, so you have to make sure your bait station is full. Given that squirrels need to adjust to something new, give it 2–4 weeks from introduction to completion. It will take the squirrels 5–9 days from exposure to die. The whole time you do the bait thing, you need to check for carcasses — 80–90% die in their burrow, but those left out risk secondary poisoning for anything that dines on them (again, consider pets, raptors, coyotes, etc).
The bait can be purchased from the county ag commissioner and you have to do a report monthly when you use it. Again, you have to get a license.
Nothing else really works. Yeah, this was all about killing squirrels, but repellents don’t work.