**Pack Rats** is a common name for several species of rodents in the genus *Neotoma*, including the **Bushy-tailed Woodrat** (*N. cinerea*) and the **Desert Woodrat** (*N. lepida*). They are medium-sized, native rodents known for their unique habit of collecting and hoarding miscellaneous items, often shiny, unusual, or human-related objects, in their massive, complex nests (**middens**). While important native wildlife, they are significant nuisance pests around human structures due to their messy nests, contamination, noise, and potential to transmit disease.
Taxonomy and Classification
Pack Rats belong to the family Cricetidae (New World rats and mice). They undergo complete life stages. They are distinguishable from non-native commensal rats (like the Norway or Roof Rat) by their slightly larger ears, softer fur, and the habit of building large, conspicuous stick nests, often including cactus spines or thorny branches for defense.
Physical Description
Adult Pack Rats are $7$ to $9$ inches long (excluding the tail), weighing $5$ to $16$ ounces.
- **Appearance:** Soft fur, typically brown or gray on top and white or gray underneath. Some species have characteristically bushy tails.
- **Nests (Middens):** Large, dome-shaped structures built of sticks, debris, cactus pieces, and whatever materials they can carry. The nests are massive and often found in rock crevices, under shrubs, or in human structures (attics, sheds, engine compartments).
- **Contamination:** Middens contain vast amounts of dried plant material, food debris, and hardened urine and fecal pellets.
Distribution and Habitat
Pack Rats are found throughout North and Central America, particularly in arid, rocky, and forested regions of the western U.S. Their habitat includes deserts, chaparral, mountains, and riparian zones. They invade human structures, especially cabins, garages, pump houses, and vehicles, seeking shelter, nesting material, and protected space.
Behavior and Conflict
Pack Rats are nocturnal and primarily herbivorous, feeding on seeds, nuts, fruits, and green vegetation.
- **Hoarding:** Their defining behavior is their strong impulse to collect objects. They often drop an existing object they are carrying to “trade” for a new, shinier, or more interesting item they encounter (the source of the “pack rat” or “trader rat” nickname).
- **Structural Damage:** They cause damage by gnawing on wires (especially in vehicles or attics), plumbing, and wooden structures. The gnawed wires in car engines can cause severe, costly damage.
- **Contamination and Health:** The accumulated fecal matter and urine in the middens pose a serious cleanup hazard. Pack Rats are reservoirs for several diseases, including **Hantavirus**, and their nests frequently harbor external parasites like fleas and ticks, which can transmit diseases to humans and pets.
Management and Prevention
Control requires exclusion, sanitation, and often trapping, with strict safety protocols for cleanup.
- Seal all holes, gaps, and openings larger than $1/2$ inch in the foundation, eaves, and vents of buildings with heavy-gauge wire mesh or metal flashing.
- Place screens over potential entry points in unused pipes and chimneys.
- Remove all exterior wood piles, junk piles, and debris that could serve as nesting material or shelter.
- **Midden Cleanup:** Exercise extreme caution when removing middens due to Hantavirus risk. **Do not stir up dust.** Wear a respirator, gloves, and wet the droppings and nest material with bleach solution before sweeping or vacuuming.
Conservation and Research
Pack Rats are important native species, and their middens (sometimes preserved by hardened urine for millennia) are invaluable resources for paleoecological research, detailing historic vegetation and climate changes. Management focuses on minimizing conflict with humans while conserving natural populations.