California Ground Squirrels – Finally A Repeating Trap That Works

What’s the Problem with Ground Squirrels?

I have been working on solutions for California ground squirrels as well as the many other variants of these invasive animals for over 40 years. Ground squirrels are responsible for a multitude of problems in all kinds of landscapes; drainage issues, levy leaks, animal leg injuries, fleas carrying diseases including rabies and even bubonic plague. Crop damage can be a huge problem. I have seen plots of corn harvested by ground squirrels, not to mention many fruits and vegetables destroyed or robbed.

UC Santa Cruz Ground Squirrel Issue 

At one point the California ground squirrels were so bad on the campus of University of California, Santa Cruz. They had undermined cement staircases, foundations, and so many other problems. They hired me for six months just to work on that problem for forty hours a week. We trapped, tried all kinds of blocking tunnels with cement, bird netting and rocks to no avail. Conflicts occurred with the fact that abandoned burrows became the home to burrowing owls, snakes and lizards. Being very careful to avoid harming these non-target animals, we examined the huge mounds for scat from owls and other secondary users.

Burrow Blocker Pros and Cons

One method that did help was filling active burrows with a slurry of fine sand and water. As the water filtered out, the fine sand would prevent burrows from being used. Though partly effective, especially protecting livestock leg injuries, this remedy required a lot of heavy equipment to move the sand and water around meadows. The main tool for this method is a machine manufactured just north of San Francisco by the company BurrowBlocker.com. They also provide service that can be expensive and usually needs repeat applications. The University eventually purchased the machine. This has helped but the vast amount of area makes it a never ending chore. One downside of this operation was hillsides where the water and sand slurry were not as effective.

Problems with Using Poisons

Other methods like applying the fumigant phostoxin or aluminum phosphide which is applied in a pellet form into the burrows and is activated by soil moisture can have a short term effect but the burrows are just reused by other nearby squirrels. Another poison method that was used in the past was to add strychnine in the body of trapped squirrels and leave it by active burrow entrances. As squirrels are cannibalistic, they would drag the body into the main burrow and consume the poison. Unfortunately the downside of this approach, as well as feeding station of type one and two anticoagulants, leads to predator poisoning worsening the situation. Other gasses like carbon dioxide, carbon monoxide pumped into burrow systems have short term effects as the burrow still exists to be reused.

Historical Holistic Approach

Another method, put forth by the Holistic Resources Management nonprofit founded by Allen Savory in Australia, is to manage burrowing pests in livestock areas by focusing feeding the livestock right on the burrows to discourage the animals and also to create a “herd effect” where the livestock is bunched and focuses on eating the proffered hay and carefully timed pasture management to optimize allowing the more nutritious perennial to dominate over the annual grasses that are a large part of the squirrel’s diet.

These annual grasses dominated due to the commonplace practice of overgrazing pasture which began back during the Spanish time in California. While researching this theory I found a notation in a Spanish ship’s log remarking on the blueish green hue of the meadows signifying the dominance of perennial grasslands. Many pastures in California are using the above method to restore pastures from overgrazing with additions of planting the preferred grasses.

Black Fox Repeating Ground Squirrel Trap

Trapping is another endless battle especially in large multi acre farmland and meadows. Ground squirrels seem to be wary of lethal traps. Therefore many farmers have turned to live trapping and then euthanizing the captives. There is a manufacturer of multiple catch traps in Northern California called the Black Fox Repeating Ground Squirrel Trap. This can be a very effective trap if used properly.

How to Trap -Black Fox Repeating Trap 

The trap is 24” by 24” by 6 inches tall with two one way doors allowing them into the trap. The doors can be locked shut and the trap placed near the burrow entrance but not too close. Then feeding baits are placed alongside but not in the trap. Baits that are effective in the spring when the squirrels emerge from winter hibernation are fruits and some nuts.

Later in the summer they begin to eat grains. The livestock feed COB (corn, oats, barley and molasses) seems most effective. Baiting continues for seven to ten days getting the squirrels used to feeding at that spot. The bait piles are a few cups of grain or COB and soon get eaten very quickly causing a feeding frenzy. This is when the trap is placed on the feeding site with the bait in the center of the trap and the doors are unlocked. When the first squirrel enters the trap many more eagerly follow. I have seen as many as fifteen to twenty squirrels caught at one time. Then the feeding and trapping cycle resumes until the population is diminished.

One note of caution is to not leave the trap open at night as often skunks will enter and be trapped, a very unpleasant experience for the animal and the trapper. 

Trapping Continued

As ground squirrels only have one litter per year the best time to trap is when the first squirrels are sited reducing the first litters. Before the trap is full of squirrels, a euthanization chamber should be constructed of wood that the trap can fit easily into and with a window to observe the process. A small hole in the side is where CO2 or vehicle exhaust is injected. The process should take 5-10 minutes.

The Automatic Trap -A24 Rat Trap

The best trap I have found comes from New Zealand by a company called Goodnature. It was developed for island bird colonies invaded by rats stealing eggs and threatening the endangered birds. The beauty of this trap, named the A24, was a series of these traps could be attached to the bases of trees and when the rats climbed up into the bottom opening of the trap throat where the bait is placed a bolt or plunger crushes the skull and the rats drops out and is eaten by predators. The trap is powered by small CO2 cylinders and has enough pressure for 24 kills hence the name A24.

This is a very successful trap for rats. It only needs to be serviced once a week or so. This eliminates the need for constant maintenance. I tested this trap for use on ground squirrels. I found the throat of the trap is too small for the ground squirrel’s larger head and was not effective. 

The Automatic Trap -A18 Ground Squirrel Trap

Then the Goodnature company came out with a larger trap used in New Zealand for stoats. A stoat is possum like animal and it is ideal for ground squirrels. This trap, named the A18 due to the larger size and force, can eliminate 18 animals prior to re-baiting and replacing the CO2 cylinder. Care must be taken, especially in California, where the grey tree squirrel is protected. Fortunately the tree squirrel and ground squirrel have very different habitats. Ground squirrels do inhabit fields and meadows more than forests except in nut tree orchards. So for range land and many farms the trap is perfect. 

Gophers Limited Inc is in the beginning stages of offering a service of installing and maintaining the A18 trap for a fee. Please check back with us if you are interested in this service.

Thomas Wittman -Founder & CEO -Gophers Limited Inc