[From the May 2017 issue of the UC IPM Retail Newsletter]

Keeping backyard chickens is becoming increasingly popular in residential areas around California. Your store may be selling pre-made chicken coops, feed, or other accessories, or you may be getting questions about rodent pests in chicken houses.

Chicken coops are sometimes associated with mild to serious rodent infestations. Rodents, such as rats and house mice, are not only predators of chickens and eggs, they can carry and transmit many diseases to both chickens and humans. For rodents, as well as most pests in and around the home and garden, advise your customers to use proactive instead of reactive management practices to address potential problems or issues.

Sanitation around the coop

Rodents are attracted to sources of food and water found in many chicken coops. To limit these attractive items:

• Remove chicken food at night, if possible. Use a mobile chicken feeder and store it in a place inaccessible to rodents. Use a rodent proof container made from heavy duty metal or plastic to prevent access.
• Keep your chicken coop as clean as possible. Remove any spilled grain that may attract rodents or other pests.
• Do not leave eggs in the coop overnight. Eggs are an excellent food source for rodents.
• Remove water from your chicken coop at night and replenish it in the morning.

Exclusion

Exclusion can be a very long lasting and effective method for combating rats and mice. Mice can squeeze through very small holes (< 1/4 inch) so it is important to repair any opening to the chicken enclosure that mice could potentially get through.

It is more difficult for rodents to gnaw on flat surfaces of durable materials. Make sure the surfaces of your chicken coop are well constructed from hard materials such as concrete, galvanized sheet (24 gauge), brick, or hardware cloth (24 gauge).

Keep all doors and hatches to chicken coops closed to prevent easy rodent access and ensure doors are well sealed. Do not use materials like plastic sheathing, wood, rubber, or green cement to seal openings. These gnawable materials don't work well and can be used as access points for rodents. Stuffing steel wool into openings is only a temporary fix.

Trapping

Trapping is a very effective method of rodent control. However, be aware that traps have the potential to injure curious birds, too. Place traps under milk crates or other areas where chickens do not have access. You can also set traps at night when chickens are inside the coop.

Rats are especially neophobic (afraid of new things), so to increase your trapping success, bait traps with a locally available food source such as chicken feed.

Using Rodenticide

Rodenticide can be applied in secured bait stations. Generally, rodenticide cannot be placed more than a specified distance from a man-made structure (usually no more than 50 feet). Homeowners do not have many rodenticide options due to restrictions on application. Chickens can eat rodent carcasses and have even been known to catch live mice. Therefore, restricting their access to rodents that may have ingested an anticoagulant rodenticide is important because rodenticides can accumulate in the rodents and if consumed by chickens, may cause them to acquire rodenticide secondarily (secondary toxicosis).

If you want to use a rodenticide but are worried about the risks, you can use an acute toxicant. These products do not have issues of secondary toxicosis associated with them. However, there are no antidotes to reverse the actions of these rodenticides. An antidote is only available when using an anticoagulant rodenticide.

If you use rodenticides as a management method, it is extremely important to completely restrict chicken access to them. If consumed by a chicken, they can cause death.

You can learn more about managing rats and mice on the UC IPM web site at ipm.ucanr.edu. For more information about raising backyard chickens, see the UC Cooperative Extension Backyard Poultry Resources web site at http://ucanr.edu/sites/poultry/type/backyard/.

-Niamh Quinn, Human-Wildlife Interactions Advisor, South Coast Research and Extension Center, nmquinn@ucanr.edu and Scott Parker, UC Master Gardener Coordinator, UCCE San Diego, saparker@ucanr.edu