December 16, 2021
  • Ground squirrels can be found throughout 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 around 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 paths and to seedling plants and high value trees by damaging bark and root systems. Ground squirrels, like other rodents, can also carry fleas, mites, and diseases.


    The ground squirrel population at Flood County Park has grown to numbers never before documented in the park. This has 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. A licensed pest management contractor will implement the plan beginning September 14, 2021 by applying carbon monoxide directly into ground squirrel burrows and sealing them.

    Frequently Asked Questions

    Q: When will this work be conducted?

    A: The most effective time to conduct this work is early in the morning and before ground squirrels exit their burrows. Because of the large number of squirrels, this work will occur in three sessions on the following days:

    • December 14, 15, 16

    • January 11, 12, 13

    • February 15, 16, 17

    An assessment will be made following the above dates to determine if further work is required.

    Q: Will the park be open when the work is being done?

    A: No. The park will be closed on the above dates to allow for efficient access and monitoring.

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

    A: Trapping is not effective for a large number of squirrels. Further, any live squirrel caught by traps must be relocated in the same area where it was caught or euthanized according to California laws. A previously proposed method of using poison bait boxes will not be used. 

    Q: Will the carbon monoxide used in burrows be harmful to humans?

    A: Carbon monoxide is a gas that has no harmful effects when present in the open air. Park staff and pest management contractor will be on site during and after fumigation to monitor conditions.

    Q: Will other wild or even domestic animals be affected by the carbon monoxide?

    A: The use of carbon monoxide directly into burrows is quick, efficient and eliminates exposure to other wild and domestic animals in the park and surrounding area.

    Q: How much damage can ground squirrels do to a large park?

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

    Q: Why don’t you just repair the damage being done by the squirrels?

    A: While burrows can be filled and paved pathways can be repaired, there is no remedy for trees already damaged. In addition, the cause of damage—ongoing burrowing by squirrels—will continue.

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

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