Pack Rats in Arizona: Identification, Risks & How to Keep Them Out
In short: pack rats — also called wood rats or trade rats — are native rodents of the genus Neotoma. Six species are commonly encountered in Arizona and other parts of the desert Southwest. Adults measure 12–14 inches including the tail. [1]
How to identify a pack rat
- Much larger than a house mouse, similar in size and shape to a roof rat — but with a long tail covered with fur or long hairs, larger eyes and ears, and a generally clean, soft appearance. [1]
- Fur is soft and may be cinnamon, brown, gray, yellowish gray or creamy buff on the upper side. [1]
- Species commonly encountered in Arizona: white-throated (N. albigula), desert (N. lepida), dusky-footed (N. fuscipes), Mexican (N. mexicana), bushy-tailed (N. cinerea) and Stephen’s (N. stephensi). [1]
Signs: the midden
- In the desert, pack rat dens are common at the base of cholla cactus, which they use as protection from predators. Ground dens measure 3 to 5 feet in height and diameter. [1]
- One animal may inhabit several nests, and in good feeding areas a den may be occupied for several years or a lifetime. [1]
- They are primarily nocturnal and solitary, except when mating or rearing young. [1]
The real risks
- Kissing bugs. Middens are common breeding sites for kissing bugs. If a midden is under or against a home, the bugs can sometimes crawl in through cracks and bite; people sensitive to the bites can develop increasingly severe allergic reactions that can become life-threatening. [1]
- Arenavirus. White-throated pack rats are reported to be carriers of arenaviruses that can infect rodents and occasionally humans; people are infected by breathing in the virus when urine, droppings or nesting material are disturbed during cleanup or structural modifications of buildings. [1] A 2001 study published in the CDC’s journal Emerging Infectious Diseases noted that Whitewater Arroyo virus, an arenavirus carried by white-throated woodrats, had recently been reported to cause fatal infection in humans. [2]
- Hantavirus. A 2007 study published in the CDC’s journal Emerging Infectious Diseases lists the deer mouse as the principal host of Sin Nombre virus in the western United States, and states that it was the only virus known to cause hantavirus pulmonary syndrome in Arizona and five other southwestern states. The same study concluded that infection risk usually is low even for people whose work involves close contact with these rodents. [3]
- Property damage. Pack rats occasionally damage vehicles and wiring in homes, and sometimes feed on garden and landscape plants. [1]
Are pack rats protected?
According to the University of Arizona Cooperative Extension, native rodents are classified as nongame mammals protected by Arizona state law; controls can be implemented in some instances when they cause significant damage to property or when potential pathogen carriers are infesting buildings. [1]
How to keep pack rats out
- Seal all cracks and gaps around doors and windows, along foundations, under eaves or roofs, and around entry points of utility lines. [1]
- Seal up buildings and the places where vehicles are housed. [1]
- Regularly inspect chollas and other cacti so pack rats don’t take up residence under them, and keep yards free of fallen fruit, leaves, twigs and other debris that serve as food and shelter. [1]
- Make sure irrigation systems work properly and repair leaks promptly. [1]
- Before cleaning up a nest or droppings, follow the CDC’s rodent cleanup and disinfection protocol (linked from the University of Arizona publication). [1]
More on rodents: how to get rid of rats · rodent control in Tucson · pest control prices in Arizona.
Frequently asked questions
How do you tell a pack rat from a roof rat?
Pack rats resemble roof rats in size and shape but have a long tail covered with fur or long hairs, larger eyes and ears, and a generally clean, soft appearance (University of Arizona Cooperative Extension).
Do pack rats carry diseases?
White-throated pack rats are reported to be carriers of arenaviruses that can infect rodents and occasionally humans, who become infected by breathing in the virus when urine, droppings or nesting material are disturbed; their nests are also common breeding sites for kissing bugs (University of Arizona Cooperative Extension).
Are pack rats protected in Arizona?
According to the University of Arizona Cooperative Extension, native rodents are classified as nongame mammals protected by Arizona state law, although controls can be implemented in some instances when they cause significant damage to property or when potential pathogen carriers are infesting buildings.
Can pack rats damage cars?
Yes, occasionally: the University of Arizona notes that pack rats occasionally cause damage to vehicles and wiring in homes.
Sources
- University of Arizona Cooperative Extension (S. Nair & D. H. Gouge), “Pack rats” (July 2023) — extension.arizona.edu
- CDC, Emerging Infectious Diseases, “Transmission of an Arenavirus in White-Throated Woodrats (Neotoma albigula), Southeastern Colorado, 1995-1999” (June 2001) — wwwnc.cdc.gov
- CDC, Emerging Infectious Diseases, “Hantavirus and Arenavirus Antibodies in Persons with Occupational Rodent Exposure, North America” (2007) — wwwnc.cdc.gov
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