University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln The aH ndbook: Prevention and Control of Wildlife Wildlife Damage Management, Internet Center for Damage

7-26-1994 Woodrats Terrell P. Salmon University of , Davis

W. Paul Gorenzel University of California, Davis

Salmon, Terrell P. and Gorenzel, W. Paul, "Woodrats" (1994). The Handbook: Prevention and Control of Wildlife Damage. Paper 8. http://digitalcommons.unl.edu/icwdmhandbook/8

This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in The aH ndbook: Prevention and Control of Wildlife Damage by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Terrell P. Salmon Wildlife Extension Specialist Department of Wildlife, Fisheries WOODRATS and Conservation Biology University of California Davis, California 95616

W. Paul Gorenzel Staff Research Associate Department of Wildlife, Fisheries and Conservation Biology University of California Davis, California 95616

Fig. 1. Eastern woodrat, Neotoma floridana

Damage Prevention and Zinc phosphide (registered in some Identification Control Methods states). Fumigants Eight species of woodrats (genus Exclusion Neotoma) occur in Not useful. (Table 1). Locally known as pack rats Woodrats can be permanently Trapping or trade rats, these are about excluded from buildings. the size of the common Norway rat. Rat snap trap. Cultural Methods They are distinguishable from Norway Live traps. rats by their hairy rather than scaly Not generally useful. tail, soft, fine fur, and large ears. They Burrow-entrance traps. Trim lower branches of citrus trees. usually have light-colored feet and Glue boards. bellies. Repellents Shooting None are registered or considered effective at this time. Limited usefulness. Toxicants Other Control Methods Anticoagulants (registered in some Destruction of dens. states).

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln Department of Agriculture and Plant Health Inspection Service Animal Damage Control B-133 Great Plains Agricultural Council Wildlife Committee Fig. 2. Range of the eastern (dark) and Fig. 3. Range of the southern plains (dark) and Fig. 4. Range of the Mexican (dark) and desert whitethroat woodrats (light) in North America. bushytail woodrats (light) in North America. woodrats (light) in North America.

Range Food Habits

The ranges occupied by woodrats are The food habits of woodrats are rela- shown in figures 2, 3, 4, and 5. tively specific for the individual spe- cies. Species such as the bushytail woodrat, for example, feed primarily Habitat on green vegetation, twigs, and shoots, whereas the Mexican woodrat feeds Each species of woodrat is generally on , , acorns, and restricted to a given type of habitat (Table 1). Woodrats may also be within its range. Woodrats occur from attracted to human food supplies in low, hot, dry deserts to cold, rocky buildings. When nesting inside build- slopes above timberline (Table 1). ings, woodrats usually continue to

Fig 5. Range of the dusky-footed (dark) and Stephens woodrats (light) in North America.

Table 1. Woodrats (Neotoma spp.) in North America.

Species: Eastern woodrat (Neotoma floridana) Species: Desert woodrat (Neotoma lepida) Species: Dusky-footed woodrat (Neotoma Description: Total length 14 to 17 inches (36 to Description: Total length 10 to 13 inches (25 to fuscipes) 43 cm). Large grayish-brown woodrat with 33 cm). Body pale to dark gray washed with Description: Total length 14 to 18 inches (36 to white or grayish belly. Tail shorter than head fulvous. Belly grayish to fulvous. Slate gray 46 cm). Body gray-brown above, gray to and body. at base of hairs. white below. Tail slightly paler below. Habitat Preference: Rocky cliffs and mountain Habitat Preference: Desert floors or rocky slopes. Dusky hairs sprinkled on hind feet. regions. Usually builds a home of sticks and House usually on ground or along cliffs. Habitat Preference: Dense , riparian debris. Food Preference: Seeds, fruits, acorns, and cac- thickets, deciduous or mixed woodlands. Food Preference: Seeds, nuts, and fruits. tus. Builds large stick houses on ground or in trees. Species: Southern plains woodrat (Neotoma Species: Stephens woodrat (Neotoma stephensi) Food Preference:Variety of seeds, nuts, acorns, micropus) Description: Total length 10 to 14 inches (25 to fruits, green vegetation, and fungi. Description: Total length 13 to 14 inches (33 to 36 cm). Body grayish buff, darker on top, 36 cm). Steel-gray woodrat with white hairs belly washed with buff. Dusky wedge on top Species: Bushytail woodrat (Neotoma cinera) on throat, breast, and feet. Blackish tail. hind foot. Tail slightly bushy on end, whitish Description: Total length 15 to 16 inches (38 to Habitat Preference: Semi-arid brushland, low below, blackish above. 41 cm). Body varies from pale gray to nearly valleys, and plains. Habitat Preference: woodlands. black. Has a long, bushy squirrel-like tail. Food Preference: Cactus, seeds, and acorns. Food Preference: Primarily juniper. Habitat Preference: High mountains. Climbs about cliffs easily. Does not normally build Species: Whitethroat woodrat (Neotoma albigula) Species: Mexican woodrat (Neotoma mexicana) houses. Description: Total length 13 to 15 inches (33 to Description: Total length 12 to 13 inches (30 to Food Preference: Green vegetation, twigs, and 38 cm). Body is gray, belly is white. Hairs on 33 cm). Gray to black in color. Tail distinctly shoots. throat and feet white. Tail whitish to brown. bicolored with white below, black above. Habitat Preference: Brushlands and rocky cliffs Habitat Preference: Rocks and cliffs in moun- with shallow caves. Builds a house 2 to 3 feet tains. Does not normally build houses. (0.6 to 0.9 m) high made of sticks and rocks. Food Preference: Acorns, nuts, seeds, fruits, Food Preference: Cactus, beans and seeds, and cactus plants. leaves of plants, especially new growth.

B-134 feed outside. Trails 3 to 4 inches (8 to most notably plague, where this Repellents 10 cm) wide from the building to the disease occurs. Dead or dying Objectionable odors from substances outside may be visible. woodrats should not be handled. like mothballs (naphthalene), or tacky substances, may make an enclosed Legal Status General Biology, area temporarily less desirable for woodrats, as for other . Like- Reproduction, and Woodrats are classified as nongame . In most states they can be wise, noxious tastes may make an item Behavior taken (controlled) when they threaten less palatable. No woodrat repellents, or damage property. Check with your however, are registered by the EPA. In Woodrats climb readily and are usu- local wildlife or agriculture depart- general, chemical repellents are not ally active at night. Most species build ment for laws and regulations specific considered a practical solution to a large stick den or house on the to your area. For example, the Key woodrat problems. ground or in trees, but some species Neotoma floridana Largo woodrat ( Toxicants live in rocky outcroppings. These smalli) was federally listed as houses are typically occupied by one endangered in 1991. Toxicants available for woodrat con- individual or by a female and her trol include anticoagulants and zinc young. One animal may inhabit sev- Damage Prevention and phosphide, registered under Special eral houses. A nest, usually made of Control Methods Local Needs 24(c) provisions. Regis- finely shredded plant material, is tered products vary among states. located within the larger house. Breed- Exclusion When using toxic baits, follow label ing usually occurs in the spring. instructions carefully. Woodrats produce 1 to 4 young per When nuisance problems occur in and litter and may produce more than 1 lit- around buildings, exclusion is the Anticoagulants are effective for ter per year in the southern parts of the most effective method of eliminating woodrat control and are especially United States. damage. Woodrats may be excluded suited for use around structures from buildings by the same methods because of their low hazard to pets Damage and Damage used to exclude Norway and roof rats and children. Most baits formulated Identification (see -proof Construction and for commensal rats and house mice Exclusion Methods). Since several give effective woodrat control. Anti- Populations generally are fairly dis- species of woodrats are agile climbers, coagulants work by interfering with persed, but economic damage to agri- all entrances to buildings, including the blood-clotting mechanism. Death cultural crops can occur in limited those at the attic level, must be closed. usually occurs 4 to 5 days after feeding areas. Agricultural damage results Cracks and openings in building foun- on bait begins. With most anticoagu- when woodrats clip small twigs and dations, and any openings for water lants, such as chlorophacinone or branches, and when they debark citrus pipes, electric wires, sewer pipes, diphacinone, feeding must occur daily and other trees and seedling and drain spouts, and vents must be for 4 to 5 days. Finely ground or meal- sapling conifers, especially redwoods. sealed. Also check for openings in attic type anticoagulant baits are recom- Loss of trees can occur. vents, broken roof shingles, or other mended. Since woodrats have a tendency to pack away items, pellet Woodrats are sometimes a nuisance gaps next to the eaves. No hole larger than 1/2 inch (1.3 cm) should be left bait should be avoided since it is often around cabins, outbuildings, and other cached at the nest site. Cached bait is infrequently used structures or unsealed. Make sure doors, windows, and screens fit tightly. If gnawing is a probably not effective in minimizing vehicles. As the name “packrat” reinvasions of the area, so it is essen- implies, they have a tendency to pack problem, edges can be covered with sheet metal. Coarse steel wool, wire tially wasted and may present hazards away small objects such as jewelry, to nontarget species. cooking and eating utensils, can tabs, screen, and lightweight sheet metal are and other items. At times, this excellent materials for plugging gaps Anticoagulants are usually put out in behavior can become a nuisance to and holes. Plastic sheeting, wood, or bait boxes, but woodrats tend to fill backpackers and others. More seri- other less sturdy materials will likely boxes with sticks and other debris. ously, woodrats may also shred be gnawed away. When rodent-proof- Therefore, use open bait containers. upholstered furniture and mattresses ing, be sure the woodrat is not trapped Bait exposed in this manner must be for lining nests, and may take up inside the building. One way to accom- placed so nontarget species, pets, and residence in parked vehicles, gnawing plish this is to install a temporary grav- children do not have ready access to it. on wires and other mechanical ity door made of sheet metal or rigid Access to the bait by pets can be mini- components. mesh wire, hinged at the top, over en- mized by inverting a wooden crate trance holes. The woodrats can push it over the bait tray. Baiting sites should Woodrats can be an important factor open to exit but cannot reenter. be located near existing woodrat run- in the transmission of certain diseases, ways, feeding sites, or nests.

B-135 Anticoagulant paraffin bait blocks Trapping method of control is time-consuming have also proven valuable for woodrat and probably of limited value. Once The majority of woodrat problems in control. Because of the paraffin, the the woodrats in an area are controlled, structures can be dealt with by using bait has more resistance to molding however, destroying their nests may one or several traps. Woodrats show caused by moisture and, therefore, reduce invasion by other woodrats. little fear of new objects in their envi- lasts longer. These bait blocks are par- ronment and are easily trapped. The ticularly useful in mountain cabins or standard rat snap trap is quite effective other structures where woodrats gain Economics of Damage for woodrats. Trap bait should be access when the building is unoccu- and Control wedged into or tied to the treadle. pied. The bait block should be nailed Good baits include nut meats, bacon or tied down to prevent the woodrat Nationally, woodrats are a minor pest. rind, peanut butter and oatmeal, from packing it away. When the label They only occasionally become numer- prunes, raisins and other dried fruit, permits, bait blocks may also be wired ous enough to cause significant agri- and biscuits. to tree limbs or other elevated loca- cultural damage. In most cases, tions. For additional information on Live catch traps, using the same baits woodrats are a nuisance around vaca- anticoagulant baits see Norway Rats, as above, can be used for woodrats. tion homes, cabins, and other out- Roof Rats, and Vertebrate Pesticides. Release of trapped animals is not rec- buildings. Their stick nests can be ommended and may be against local extensive and their physical presence In agricultural situations, zinc phos- fish and game regulations. Also, many and droppings are often objectionable. phide is a Restricted Use Pesticide and studies have shown that animals Woodrats can carry diseases and ecto- must be applied by a certified applica- released into new areas often die from parasites. Therefore, close association tor. Steam-rolled oats or oat groats exposure, predation, or competition with humans is undesirable. In most treated with 2.0% zinc phosphide are with resident animals. nuisance situations, control can be generally very effective on woodrats. accomplished by the resident or Usually, tablespoon (4 g) amounts are Burrow-entrance traps such as the No. homeowner. scattered in runways near the nest site. 110 Conibear® trap may also be useful Zinc phosphide bait should be applied for woodrat control. The trap is placed in late afternoon just prior to in nest openings or other restricted Acknowledgments woodrats’ night-time feeding. Feeding travelways and is triggered when the on a sub-lethal amount of zinc phos- woodrat passes through the trap open- Figure 1 from Schwartz and Schwartz (1981). ing. When traps are set in this manner, phide bait can result in bait shyness. Figures 2, 3, 4, and 5 adapted from Burt and Therefore, do not use zinc phosphide baiting is not necessary, but care must Grossenheider (1976) by David Thornhill. more than once per 6-month period. be taken to avoid nontarget animals. In some cases, the use of second gen- Glue boards are also effective for trap- For Additional eration anticoagulants (for example, ping woodrats. These work on the Information brodifacoum, bromadiolone) or other same principle as flypaper; when a rat toxicants (cholecalciferol) may be per- attempts to cross a glue board, it gets Burt, W. H., and R. P. Grossenheider. 1976. A mitted for woodrat control. Based on stuck. Glue boards tend to lose their field guide to the mammals, 3d ed. Section 2 of FIFRA (Federal Insecticide, effectiveness in dusty areas, and tem- Houghton Mifflin Co., Boston. 289 pp. perature extremes may affect the tacki- Fungicide, and Rodenticide Act), EPA Linsdale, J. M., and L. P. Tevis. 1951. The dusky- ruled that it is legal, unless otherwise ness of the adhesive. In many cases, footed wood rat. Records made on Hastings specifically prohibited, to use a pesti- woodrats trapped on glue boards will Natural History Reservation. Berkeley, cide against a target species not listed not die immediately. If they don’t, they California. 675 pp. on the label if the label directions for a can be euthanized by placing the board Schwartz, C. W., and E. R. Schwartz. 1981. The listed pest are followed. The site to be in a plastic bag and adding carbon wild mammals of Missouri, rev. ed. Univ. treated must be mentioned on the label dioxide gas. Missouri Press, Columbia. 356 pp. and there must be reason to believe the Vorhies, C. T., and W. P. Taylor. 1940. Life Remember, all traps and glue boards application will be effective. For history and ecology of the white-throated should be placed so that children, pets, Neotoma albigula Hartly example, the use of cholecalciferol to wood rat, , in relation and other nontarget animals do not to grazing in Arizona. Univ. Arizona Tech. control woodrats in or around build- have access to them. Bull. 49:467-587. ings could be permissible because the Wiley, R. W. 1980. Neotoma floridana. . label lists Norway or roof rats and Other Methods Species. 139:1-7. specifies in or around buildings. Not all states accept the EPA ruling. Check Destroying woodrat nests has been with the appropriate pesticide enforce- suggested as a method of control. Editors ment agency prior to pursuing this When a nest is destroyed, the animals Scott E. Hygnstrom course of action. may run for cover, thus exposing them Robert M. Timm to predation by humans or dogs. This Gary E. Larson

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