photo of Coyote running through field.


After numerous sick animals were observed in the preserves around 2013, California Department of Fish and Wildlife (CDFW), with assistance from Midpen staff, linked the illness and death of many bobcats specifically to second-generation anticoagulant rodenticides (SGAR). Bobcats and other predators like coyotes, hawks, owls and kites can eat hundreds of mice and rats a year. If the preyed upon rodents have consumed SGAR pesticides, then those toxins can then accumulate in a predator's body, weakening their immune systems and leading to them become more susceptible to diseases like mange, and if consumed in large enough quantities can be fatal. 

Midpen began educating preserve neighbors about the effects of the commonly available pesticides on wildlife and joined the ongoing effort to lobby the California State Legislature in limiting their use. In 2014, the legislature passed AB 2657, limiting access to SGARs to individuals with state-issued pest control licenses. Midpen also took action with its award-winning IPM Program, mandating the use of non-chemical techniques first whenever possible to protect human and environmental health. Additionally, in 2020, Midpen supported AB 1788, “The California Ecosystems Protection Act,” which prohibits most uses of second SGARs. 

In recent years, there have been indications that bobcat populations in the preserves are now healthier and have not been observed with signs of mange. However, rodenticides are still being used. A recent CDFW study found that between 70 to 90% of tested wildlife were found to have SGARs in their systems. Midpen continues to work with other agencies and organizations to limit SGAR rodenticides and promote alternative pest control methods. 

Map of the range of bobcats and coyotes from Rancho San Antonio Open Space Preserve

What can you do? 

There are more effective means of rodent control through property control and natural solutions rather than using rodenticides. Remember, preventing rodents from establishing on your property is much more effective and safer to wildlife than use of pesticides. 

  • You can help by hardening your home against rodents by sealing any openings or entrances to your residence.  

  • Remove rodent-friendly habitats such as English ivy, iceplant and other natural habitats. Clear any fallen fruit as to not attract rodents 

  • Remove rodent access to any food sources such as pet food, chicken coops, garbage and compost. Remember, rodents can gnaw through thin plastic or cardboard containers.  

  • When active pest control is necessary, consider manual traps such as snap and box traps to control rodent populations in your neighborhood.   

  • Visit the website of Raptors Are the Solution, a Midpen partner, for more information. 

  • Install an owl box, to attract natural predators who limit rodent populations. Click here for directions on building and installing a barn owl box.

  • If working with a pest control company, request to review and approve a list of any pesticides that are being used. One common compound, known as Diphacinone, can harm non-target wildlife. Check the active ingredients of proposed pesticides to avoid this compound. 

Natural Resources Protection and Restoration
Natural Resources