Rodent Control

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p34 poisoned NPSThe City of Thousand Oaks has taken steps to protect people, pets, and animal predators by halting all City use of rodenticides. The City Council voted unanimously on April 14, 2015* to discontinue the use of anticoagulant rodenticides in operations and maintenance of municipal facilities and landscape except under circumstances of extreme risk of danger to the health of our citizens or damage to infrastructure. This vote is one more step towards the City goals of implementing a comprehensive Integrated Pest Management (IPM) program and reducing potentially toxic pollutants.

When residents have unwanted rodents on their property, poison is often their go-to solution. But most people don't realize the danger this choice poses not only to children and pets, but also to wildlife. Anticoagulant rodenticides  - i.e., rodent poisons that stop blood clotting to create lethal internal bleeding - used in these substances don't just kill rats, gophers and ground squirrels. Non-target predators such as hawks, owls, coyotes, bobcats and mountain lions feed on the poisoned rodents and become severely ill or die themselves. It may take several days for a rodent to die, making it slower and easier prey for a larger mammal or raptor in the meantime. Unfortunately, once the dying rodent is eaten, the poison passes into the predator's body. 

There are two general types of anticoagulant rodenticide: first-generation anticoagulant rodenticide (FGAR) and second-generation anticoagulant rodenticide (SGAR). First-generation anticoagulant rodenticides were developed in the 1940’s and require multiple ingestions to take effect. SGARs have been designed to take effect after a single ingestion, persisting in the animal’s liver long after consumption if they do not consume additional, deadly doses. These toxins pose a particular threat to predators and ecosystem health: secondary poisoning. Secondary poisoning occurs when one individual comes in contact with another individual that has been poisoned, or has poison in their system; most often through predatory consumption (see infographic from the NPS). 

Animals aren’t the only species at risk to the dangerous effects of rat poison. According to the Center for Biological Diversity10,000 kids are poisoned by rat poison each year in their own homes. To combat this home (and environmental) health risk, the Environmental Protection Agency (EPA) took legal action and banned the residential use and sale of some SGARs. The California Department of Pesticide Regulation followed suit; and in October Governor Jerry Brown signed AB 2657, which bans the use of second-generation anticoagulant rodenticides in California state parks, state wildlife refuges, and state conservancies.

The rodenticide problem was the subject of a seminar on alternatives to rodenticides hosted by Ventura County Supervisor Linda Parks and State Senator - and environmental champion-  Fran Pavley. Senator Pavley kicked off the symposium by presenting her monthly Environmental Sustainability Award to the Oak Park Unified School District, which banned the use of rodent poison on its campuses.

Almost all our predators are poisoned

Research presented at the seminar was undertaken by the University of California, Cal Poly San Luis Obispo and the National Park Service (NPS) over more than a decade in and around the Santa Monica Mountains National Recreation Area (SMMNRA). It documents widespread poison exposure in coyotes, bobcats and mountain lions. Rodenticide exposure was the second leading cause of death during a 9-year coyote study, second only to collisions with automobiles. Over 83 percent of coyotes tested positive for poisoning. Researchers also found anticoagulant rodenticides present in 90 percent of mountain lions and 92 percent of bobcats, which indicates compromised predator health in the entire region. If not killed outright by the poison, it weakens the predators' immune systems, making them susceptible to secondary diseases such as mange and infection.

Integrated Pest Management is the Solution
Some experts assert that poison does not kill off the pest population, but rather only makes it cycle up and down. Integrated pest management, or IPM, is an alternative, ecosystem-based strategy. It focuses on long-term prevention of pests and their damage through a combination of techniques such as biological control and habitat manipulation. IPM is a win for facilities management, since it cuts costs compared to poison-based rodent control programs and is completely safe to use. (See also our web page on Integrated Pest Management.)

At the symposium, Pepperdine University, Topa Mountain Ranch, Oak Park USD and the Ventura County Watershed Protection District all presented IPM techniques they have successfully used on their sizable properties to reduce rodent populations. Some of the methods they have employed include:

  • habitat modification;
  • removal or thinning of cover;
  • exclusion (e.g., closing access points, installing wire mesh, raising plant beds, etc.);
  • "burrow busters" (i.e., creating explosions in burrows using underground gas lines);
  • owl and kestrel nesting boxes, using natural predators to kill off the rodent population;
  • placement of predator urine as a deterrent;
  • placement of aromatic annual herbs, such as mint, lavender and catnip and perennial plants that repel mice, such as amaryllis, lavender (Lavandula) or daffodils (Narcissus);
  • water troughs;
  • metal kill traps; and
  • predator perches to encourage rodent-killing raptors.

What you can do at home
If you discover you have rodents on your property, first try to identify the species. Then figure out where the species gets its food, shelter and water, which will help with finding the best methods for removal. For instance, if the rodent spends a lot of time underground, placing traps above ground isn’t the best option.

There are many other IPM approaches that can be effectively used in a residential setting, including the following techniques:

  • Population Control: limit all access to food, water, and shelter. The most important thing you can do is to keep all food sources, including bird seed and pet food, in secure, locked containers. Trash, recycling and compost bins should be kept closed at all times.
  • If you can't give up feeding birds in your garden, consider getting a "squirrel baffle," a large plastic or metal device placed on the pole of a bird feeder. It is designed to deter squirrels, raccoons and other small mammals from accessing the bird food.
  • Seal any holes that lead indoors with metal mesh or other similar effective material.
  • Maintain landscaping. Thin out brush where the rodents hide. Many rodents, including rats and voles, do not like visibility or change and will often leave if you modify or thin the cover in the area where they are nesting.
  • Predator urine can be purchased online from a number of different vendors on Amazon and placed as a deterrent in areas where you have seen pests.
  • Kill traps are also effective choices, since it is illegal in California to trap and move live animals.[1] The Pacific Coast Business Times recently reported on the GopherHawk, a new poison-free gopher and mole trap available on Amazon. This product, designed and manufactured in Oxnard, uses a probe and auger to set an underground snare in the rodent's tunnel. When the trigger is moved, it snaps and kills the gopher instantly, displaying an indicator above ground so the owner can remove it.
    Types of Kill traps you can employ:
    • Electrocution Traps: traps that kill rats by electrocution
    • Live Traps: least preferable trap option, as once the rodent is caught, it remains alive and must be handled appropriately
    • Snap Traps: A simple and well tested method for catching smaller rodents.
  • Natural Predators: if you have the space, install owl boxes and allow a natural predator to manage the population of rodents

By employing these poison-free techniques to root out rodents on your property, you will not only be protecting pets and kids, you will also be doing local wildlife a huge favor.

To properly dispose of any old or unwanted rodenticides, pesticides, or other toxic or hazardous waste, please make an appointment to take the material to the City’s Household Hazardous Waste Facility.

For more information:

  • Raptors Are The Solution (RATS): Has information on the devastating impact rodenticides have on wildlife who frequently eat rodents that have been poisoned and are then poisoned themselves.
  • Urban Carnivores: A valuable web resource for more in-depth research on rat poisons
  • Rats: UC Davis’ one page PDF with suggested alternatives to rat poisons.
  • Click here and here and here for related articles from the Thousand Oaks Acorn.
  • Click here for local coverage on the topic from the LA Times
  • Poison Free Malibu is a great resource for more information on rodent poison, IPM techniques and links to local extermination companies that employ non-toxic IPM methods

[1]  California Department of Fish and Game, California Code of Regulations Title 14, §465.5. Use of Traps. Immediate Dispatch or Release. All fur bearing and non-game mammals that are legal to trap must be immediately killed or released. Unless released, trapped animals shall be killed by shooting where local ordinances, landowners, and safety permit. 


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