Flooded Park Pest Management FAQs

Ground squirrels can be found in open, grassy fields in rural and urban areas and are different from tree squirrels. While tree squirrels inhabit trees, ground squirrels create underground burrows usually about 4 inches in diameter and between 5 and 30 feet long where they rest, store food, and raise young.

Oversized populations of ground squirrels cause damage to facilities and walking trails as well as to valuable seedlings and trees by damaging bark and root systems. Ground squirrels, like other rodents, can also carry fleas, mites, and disease.


Flood County Park’s ground squirrel population has reached numbers never before documented in the park. This caused damage to walkways and trees, including oaks and redwoods. A pest management plan to reduce the number of ground squirrels has been developed in coordination with our natural resource management staff. The Department has contracted with the United States Department of Agriculture (USDA) Wildlife Services Division to conduct the next phase of pest control during which burrows will be fumigated with a prescribed amount of sodium nitrate and charcoal. Live traps will be set near the burrows in case the squirrels come out during the fumigation. This approach allows the USDA to release any animal that may have been trapped other than squirrels. These techniques are safe for the public, pets, and non-target wildlife outside burrows. No poison or bait boxes will be used in this effort.

Frequently Asked Questions

Q: When will this work be done?

A: The most effective time to do this work is early in the day before the gophers emerge from their burrows. Due to the large number of squirrels, this work will last five days starting Monday September 19 and will continue until Friday September 23. During this period, the park will be closed. An assessment will be made following the work to determine if other measures are necessary.

Q: Will the park be open during the works?

A: No. The park will be closed to all activity, including foot traffic, on the above dates to allow for effective access and monitoring.

Q: What other population management methods have been considered? What about moving ground squirrels to another park or open space?

A: Earlier this year, the Department fumigated the burrows with carbon monoxide. However, this method was not effective given the number of burrows and squirrels. Trapping is not effective for large numbers of squirrels. Additionally, any live squirrels captured by traps must be relocated to the same area where they were captured or euthanized according to California law. A previously proposed method of poison bait boxes will not be used.

Q: Is the fumigation compound used in burrows harmful to humans?

A: No. Fumigation material has no harmful effect on humans or any other animals outside of open burrows. Park and USDA staff will be on site during and after fumigation to monitor conditions.

Q: Will other wild animals or even domestic animals be affected by burrow fumigation?

A: No. Fumigation directly in the burrows is fast, effective, and eliminates exposure to other animals – wild or domestic – outside the burrows in the park and surrounding areas.

Q: How much damage can ground squirrels cause in a large park?

A: Since the current ground squirrel population is larger than documented in the park in previous years, a significant amount of damage has occurred as seen in the photos above.

Q: Why don’t you just fix the squirrel damage?

A: Although burrows can be filled in and paved walkways can be repaired, there is no cure for trees that are already damaged. Also, the cause of the damage – the continuous digging of squirrels – will continue.

Q: Won’t the number of ground squirrels increase after the pest control plan is completed?

A: The department will monitor activity, particularly from spring to early summer when ground squirrels are born. Typically, squirrels will produce one per litter each year. Litter size can be five to eight cubs. If necessary, a second management plan will be developed and implemented.

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