September 14, 2022
  • 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.

    Trees with a wooden fence and dirt floor
    Root of tree and dirt
    Small tan and brown building showing water damage due to flood
    Hole in the dirt against sidewalk caused by flood

    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. The Department has contracted with the U.S. Department of Agriculture's (USDA) Wildlife Services Division to conduct the next phase of pest management in which burrows will be fumigated with a prescribed amount of sodium nitrate and charcoal. Live traps will be set near burrows in the event squirrels exit during fumigation.  This approach allows the USDA to release any animal that may have been trapped other than squirrels. These techniques are safe to the public, domesticated animals, and non-targeted wildlife outside of burrows. No poison or bait boxes will be used in this effort.

    Frequently Asked Questions

    Q: When will this work be conducted?

    A: The most effective time to conduct this work is early in the day before ground squirrels exit their burrows. Because of the large number of squirrels, this work will take five days beginning Monday, October 31 and continuing through Friday, November 4. During this time the park will be closed. An assessment will be made following the work to determine if further action is required.

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

    A: No. The park will be closed to all activity, including foot traffic, 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: Earlier this year, the Department fumigated burrows using carbon monoxide. However, that method was not effective given the number of burrows and squirrels. 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 poison bait boxes will not be used. 

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

    A: No. The fumigation material has no harmful effects on humans or any other animal outside of burrows in the open air. Park and USDA staff will be on site during and after fumigation to monitor conditions.

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

    A: No. Fumigation directly into burrows is quick, efficient and eliminates exposure to other animals -- wild or domestic -- outside of burrows 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.