from the Spring 2022 Newsletter.
by Alan Myklebust
Multiple neighbors have reported problems with roof rats, both small and large infestations. Roof rats are also called fruit rats for their tendency to eat citrus and other fruits commonly grown in gardens in Arizona. Roof rats are not native to Arizona but have adapted well to our climate and the fruit trees commonly found in many neighborhoods. They have been a significant problem in Phoenix and its suburbs for many years, first seen in the Arcadia neighborhood (Phoenix) in 2002. Neighbors in Blenman Elm have now been trapping roof rats for the past several years, and they appear to be spreading across Tucson.
Roof rats are technically black rats (Rattus rattus), although they can be various colors. They are identified by their large ears and long tails, often as long as their bodies. They are called roof rats because they often inhabit attics and crawl spaces above ground. They also climb trees and bushes, especially fruit trees. However, they will also create underground burrows and nests.
Late winter and spring is often the time they become more active, as the weather is cool and fruit trees ripen in Arizona. They are generally nocturnal and elusive, avoiding detection as much as possible. However, there are multiple ways to detect their presence on your property. The most obvious indications that roof rats are active is half eaten fruit on the ground or still in a tree. But roof rats will also eat some succulent plants and often eat bird seed from feeders or blocks. Sometimes they create burrows under vegetation in gardens which will cause noticeable soil disruption. They can nest in woodpiles, and frequently inhabit attics and rooftop crawl spaces. Some residents have heard them scurrying around at night and observed them climb ladders or trees to get to the quiet and warm spaces above homes.
The number one way to prevent roof rats on your property is to make it inhospitable to them, and do not provide them with a food source (starve them). If you have fruit trees, pick ripened fruit (or even unripe fruit), and do not let it remain on your trees or fall to the ground below. Don’t leave uneaten pet food outside overnight and pick up pet feces regularly. Keep garbage containers tightly covered. Keep your indoor bulk food (and pet food) in sealed containers. Limit and control your bird feeders. Clean up below bird feeders and do not leave fruit for birds overnight.
Secondly, avoid creating cluttered areas like woodpiles, or other debris. Store wood at least a foot or two above ground level. Limit or use proper techniques for composting. Roof rats often dwell and feed on compost. Trim bushes and trees such that the area beneath is observable. Trim dead palm and other tree branches since roof rats are attracted to palm skirts and hollows in trees. Roof rats are also attracted to oleander thickets in the summer. Rake your yard of leaves and debris. Roof rats inhabit cluttered areas.
Next, be sure that your home is impenetrable to roof rats. They can squeeze through extremely small spaces. Diamond stucco mesh (sold at hardware stores) is sufficient to block them. Seal or caulk any areas that access your roof and attic such as ventilation and sewer stacks. Use steel wool or copper mesh to block them.
Traps are often necessary when roof rats are present. Hardware stores sell effective traps at reasonable prices, or they can even be purchased online. Avoid using poisons in traps (or anywhere else) and place them strategically on your property. Try to avoid placing traps where other animals, pets, small children, and birds might access them. Out buildings like carports, garden sheds, garages, water heater enclosures, and greenhouses are good locations. Leave the traps in place for at least a week or longer. Roof rats might avoid the traps initially, but eventually they will overcome their fear and investigate. Bait the traps with peanut butter or a commercial product such as Rat X which is not poisonous but attracts vermin and eventually dehydrates them. Once you trap a rat, dispose of it quickly to avoid the smell, and reset the trap. If you trap one, there are most likely more around.
If you notice rats, let your neighbors know! Eradication is difficult if proper strategies aren’t accomplished collectively. It takes a concerted effort by all of the neighbors in an area to control roof rats.
UArizona Cooperative Extension Service pamphlet: Roof Rats: Identification, Ecology, and Signs
For Pest Management Professionals and Environmental Health Professionals
Poisoning rodents is very harmful to our birds of prey (hawks, roadrunners and owls) and mammals of prey (bobcats and coyotes), despite what pest control companies might say. When rats take up residence, exclusion and trapping are the wildlife friendly options.
-– Ben Wilder
Donate your excess fruit
Another way to help with your excess citrus that may be attracting roof rats is to contact the Iskashitaa Refugee Network to donate your fruit. www.Iskashitaa.org/fruit-donor-form