Secondary Poisoning — How Rodenticide Kills Hawks and Owls in Southern California
Rodenticide bait — the poison used in many commercial and DIY gopher, mole, and rodent control products — is one of the leading documented causes of raptor death in California. The mechanism is secondary poisoning: a hawk or owl eats a rodent that has consumed the bait, and the poison accumulated in the rodent's body then kills the bird. This is not a theoretical risk. Wildlife rehabilitation centers throughout Southern California document hundreds of raptor deaths from secondary rodenticide poisoning every year.
How Secondary Poisoning Works
Most rodenticide baits used in pest control are anticoagulants — they work by preventing blood from clotting, causing internal bleeding over several days. When a gopher or mole consumes a lethal dose of anticoagulant bait, the poison accumulates in the animal's tissue. The animal does not die immediately — it continues moving through its tunnel system for days while lethally poisoned, and it may behave abnormally, making it easier for predators to catch.
When a red-tailed hawk, barn owl, or Cooper's hawk catches and eats a poisoned gopher, the anticoagulant from the gopher's tissue transfers into the bird's body. If the bird eats multiple poisoned rodents — which is common during active infestations — the accumulated dose can be lethal. The bird then dies from the same internal bleeding the rodenticide was designed to cause in the target animal.
Which Animals Are Affected
Raptors are the most heavily affected because they are the primary predators of the burrowing rodents that are the target of most pest control bait. Red-tailed hawks, barn owls, great horned owls, Cooper's hawks, and American kestrels all hunt gophers and moles regularly in Southern California residential areas. All are documented victims of secondary rodenticide poisoning.
Non-target mammals are also affected. Coyotes, foxes, bobcats, and domestic dogs and cats that eat poisoned rodents — or that eat other animals that have eaten poisoned rodents — can all suffer secondary poisoning. California condors, which scavenge rodent carcasses as part of a broad diet, have died from secondary rodenticide poisoning in documented cases.
The Irony of Killing Your Best Natural Pest Control
Barn owls and red-tailed hawks are among the most effective natural predators of gophers in Southern California. A single barn owl family consumes an estimated 1,000 or more rodents per year. A resident red-tailed hawk pair controls gopher populations in the territories they actively hunt. When rodenticide bait kills these birds, it removes the natural predation pressure that helps keep gopher populations in check — making the pest problem worse over the long term, not better.
Why Rodent Guys Does Not Use Poison Bait
Rodent Guys uses professional trapping and carbon monoxide treatment only. No rodenticide bait of any kind, on any job. Carbon monoxide is applied directly into active tunnel systems and dissipates completely underground — it has no pathway to secondary poisoning because it does not accumulate in tissue. Traps remove animals mechanically with no chemical residue. Our methods are as effective as bait-based approaches for eliminating active infestations, and they do not kill the hawks, owls, and other wildlife that share Southern California's residential landscapes with us.
What You Can Do
If you use any DIY gopher or rodent control products, check the label for anticoagulant active ingredients — brodifacoum, bromadiolone, diphacinone, and chlorophacinone are the most common. Consider switching to trap-based or CO-based professional service. If you see a raptor behaving abnormally — unable to fly, sitting on the ground, lethargic — contact a wildlife rehabilitation center. The California Raptor Center and local wildlife rehab organizations throughout Southern California accept injured raptors and can assess for rodenticide exposure.
Related Articles
- Trapping vs. Poison — Why Chemical-Free Gopher Control Is Better
- Why Gopher Poison Is Dangerous for Dogs and Cats
- Why Pet-Safe Gopher Control Matters
Frequently Asked Questions
It is well-documented and common. Wildlife rehabilitation centers throughout California treat hundreds of raptors annually for rodenticide exposure, and many do not survive.
No. Carbon monoxide dissipates in the tunnel system and does not accumulate in tissue. There is no secondary poisoning pathway from CO-based gopher control.
Some anticoagulant rodenticides have restrictions in California, particularly near wildlife areas. Regulations change periodically. Check current CDPR guidelines for the most up-to-date information.
Call 909-599-4711 for effective gopher control that protects your yard and the wildlife in your neighborhood.