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January 1993

Controlling Mountain Beaver Damage in Forest Plantations

David S. de Calesta Oregon State University Extension

Ralph E. Duddles Oregon State University Extension

Michael C. Bondi Oregon State University Extension

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Part of the Environmental Sciences Commons de Calesta, David S.; Duddles, Ralph E.; and Bondi, Michael C., "Controlling Mountain Beaver Damage in Forest Plantations" (1993). Other Publications in Wildlife Management. 54. https://digitalcommons.unl.edu/icwdmother/54

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 Other Publications in Wildlife Management by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Extension Circular 11 44 Reprinted January 1993 Woo and

Reforestation F Controlling Mountain Beaver

DamaaeM inForest Plantations D.S. deCalesta, R.E. Duddles, und M.C. Bondi

Damage to conifer regeneration by mountain beavers, more commonly called boomers, results in significant losses in Western Oregon annually. Most of the damage is to 1- to 5-year-old conifer seedlings. Where populations are high, repeated clip- ping by mountain beavers can cause loss of production through poorly stocked acres-even reforestation failures. Damage can continue on saplings up to 15 to 20 years old; however, newly planted seedlings are particu- larly vulnerable. In a few instances, extensive burrowing can undermine the roots of larger trees enough to topple them. This publication will help you design a program to reduce mountain beaver damage in your forest planta- Figure I .-Adult boomer. Although also called mountain beaver, it's not related to the true beaver. tions to acceptable levels. First, we discuss mountain beaver biology to familiarize you with some of the As burrowing animals, mountain A typical mountain beaver burrow animal's behavior; this will help you beavers don't construct well-defined system is 80 to 100 feet long, with a control its damage. Then we discuss trails aboveground. They have system of lateral tunnels 6 to 10 control techniques. powerful shoulders and large, heavily inches below the ground. Frequently, Finally, we discuss integrating clawed front feet adapted for burrow- control methods with silvicultural ing. Other adaptations include small David S. decalesta, fonner Extension practices as a way to maximize the eyes and ears and short, dense fur for effect of your control program. wildlife specialist; Ralph Duddles, repelling soil particles. Extension agent (forestry), Coos and Mountain beavers have poor eye- Curry counties; and Michael C. Bondi, Biology and habits sight in full daylight, but they have a Extension agent (forestry), Clackamas keen sense of smell and long whiskers County; Oregon State University. Ron ~~~~~~i~beavers (&lodontia rufa) Durham, regeneration forester, North are medium-sized rodents about 12 for navigating dark tunnels. They'll OccasiOnall~forage for foOd during Bend, Oregon, provided generous assis- inches lang, weighing 2 to 3 pounds tance with background" information based at maturity (figure 1). the day, but they're mainly nocturnal. on his extensive trapping experience. Oregon State Universit y Extension Service a portion of the burrow will run directly underneath logs; here, it's Open at the top. This opening to the system, which rnay extend for 10 feet or more past the log, is a good trap-setting location. Mountain beavers construct Underground chambers for nests, food storage, and fecal deposits. They pile mounds of excavated soil on the surface called kickouts. The burrow system and kickouts are positive evidence of their presence. Burrows of other animals (voles, moles, pocket gophers, and ground squirrels) are much smaller and different in appear- ance. Mountain beavers are commonly found on most timbered lands west of the crest of the Cascade Range. Preferred habitats are sites with deep Figure 2.-Presence of rnountain beaver is often indicated by clipped seedlings. soils for tunneling, abundant supplies of preferred foods, and cool, moist surroundings. Habitats rnay range from old growth forests to riparian kits. Because of this low reproductive The low potential for rapid zones and clearcuts. capacity, it's possible to reduce repopulation means that lethal control Especially preferred habitats are populations through lethal control measures started early and thoroughly cool, moist stream bottoms and north measures (trapping or poison baits), (preferably before time of planting) slopes that are characterized by a and to keep population levels rela- can reduce populations enough to give heavy understory of swordfern, vine tively low with continued followup outplanted conifer seedlings a good maple, and salmonberry. Red alder treatment. chance for survival. stands frequently support high Mountain beavers are solitary in densities of mountain beaver. nature, excluding other adults from ldentifying damage Mountain beavers feed on a variety their burrow systems except during the breeding season (February-March). If you're finding damage in your of plants, depending on availability. plantation, it's important to correctly Preferred foods include swordfern, The young stay with the mother until fall of the first year, when they're identiSl the pest responsible. huckleberry, bracken, salal, Oregon Misidentification can lead to inappro- grape, thimbleberry, salmonberry, forced from the maternal burrow to make it on their own. priate (possibly illegal) control elderberry, miners lettuce, and methods that can endanger and harm grasses. They'll eat woody plants, They rnay move as much as 600 feet or more in searching for a suitable nontarget species. The results will be including vine maple, alder, and lack of control and a waste of time, conifer seedlings. When food supplies new habitat, where they rnay adopt an abandoned burrow or dig their own. money, and effort. are short, they're one of the few Surrounding habitat, burrow animals that will eat even Sitka spruce Mountain beavers lack the mobility to travel great distances. Their home systems with fresh looking kickouts, seedlings. piles of swordfern and vegetation, and They rnay clip food plants from ranges rarely exceed 1 acre. Burrow systems are exclusive to each animal, damage to conifer seedlings-these ground level to as high as 10 feet or are all good indications that mountain more aboveground, and they usually but they rnay border or overlap with others. beaver are present. Smaller seedlings take them to the burrow for eating or such as plugs and 2-0's are often storage (figure 2). Densities of animals rnay be as high as five per acre in ideal habitat; clipped about 1 inch above ground It's common to find swordfern level (figure 3). fronds and other foliage piled at a however, fewer than one per acre is more common. Mountain beavers On larger seedlings, such as burrow's entrance to dry for a day or plug-l's, 2-13, or 3-O's, mountain two before mountain beavers move rarely move far from established burrow systems. beaver often clip off lateral branches them inside, to eat in safety from close to the stem with the same predators. They get most of their Recognizing mountain beaver habitat, including the presence of characteristic 45" angle. On older water from the food they eat. trees, they rnay use the clipped Unlike most rodents, mountain preferred foods, can help you evaluate the potential for problems on your laterals as steps to climb the seedling beavers have a low reproductive rate. until they can clip off the leader. Females don't bear young until after regeneration sites. Knowing their the second year, and they usually bear densities and damage on adjacent sites only one litter a year with two to four helps you evaluate the potential for problems. It's preferable to use a toothed brush blade to pile slash. A brush blade can uproot standing brush, which minimizes resprouting. It also reduces topsoil disturbance and carries less dirt into your slash piles. Windrows and piles of slash create excellent cover for mountain beaver, from which they can easily move to feed on newly planted trees. It's imperative to burn slash piles promptly and thoroughly to reduce this hazard. A good followup weed control program, using appropriate herbi- cides, is important to prevent reestab- lishment of vegetation that mountain beaver use for food and cover. This Figure 3.-Mountain beavers clip seedlings with a sharp 45' cut. Grooves that rnatch the will minimize the attractiveness of '18-inch width of their incisor teeth are often visible. your site to animals and will maxi- mize the effectiveness of your other control measures. Trapping is the most common Mountain beavers commonly strip Lack of lush vegetation for food method for effective control of or peel the bark off the base of older source creates a water shortage mountain beaver damage. It's labor- saplings. They may also chisel the because the animals derive much of intensive, however. You must check base in the manner of the true beaver, their water from what they eat. This traps every few days, and you must toppling saplings up to 10 feet high. forces them to forage greater distances, periodically move them to new It's important not to confuse other making them more susceptible to locations. types of damage with that of moun- predators. Trapping is effective, but you must tain beavers. Dens and runways are more visible be persistent to be sure that you've on properly prepared ground. This removed most of the mountain Rabbits tend to push over seed- exposure, combined with the in- beavers in the area. Survivors will lings and clip laterals farther out creased activity, makes trapping easier continue to damage trees, and they'll toward the end at a secondary and more effective. repopulate the area if you don't carry branching point. They also scatter You can reduce or eliminate out good vegetation management their droppings around the damaged mountain beaver habitat by burning together with trapping. seedlings, while mountain beavers logging debris. A hot broadcast burn The trap most commonly used is usually leave theirs belowground in may actually reduce the number of the body grip Conibear 110 (see their burrow system. Rabbit droppings animals by suffocating them. Burning figure 4). are 318-inch spheres that look like removes the brush species used for It's important to select the right they're made of particle board. food and retards their resprouting for location to set the trap. Look for fresh Porcupines. The best tool for 1 to 3 vears. mountain beaver sign. Recent cuttings separating mountain beaver damage Broadcast burning on small wood- of swordfern, salmonberry, and from that done by porcupines is the land properties has some limitations. conifer seedlings stacked next to exit difference in width of incisor teeth It may be difficult to plan an effective holes indicate active runways. marks on the cambium: Yi inch for burn on small areas of onlv a few For indications of recent, frequent mountain beavers; 3/16 inch for acres. Burning north-facing slopes use, look for runways that: porcupines. The presence of large, that contain mostly alder slash is are clean with no spider webs, hard oval scats is also good porcupine difficult without ideal weather have no litter or leaf accumulation evidence. conditions. or grass growing, and Broadcast burning requires are hard-packed and shiny. preplanning, labor, and equipment. It Controlling damage also requires compliance with your Insert the set trap into a runway. A Site preparation. Proper site area's smoke-management regula- good place to set traps is at openings preparation can play an important role tions-and proper liability protection in the roof of runways. in reducing the potential for mountain in case the fire escapes your property Enlarge the opening, if necessary, beaver damage in your plantations. boundarv. so the trap just fits in the runway. It's Whether you accomplish this by If the areas you plan to reforest are important to secure your trap so it burning, mechanical piling, or relatively flat (30% slope or less), and won't fall over. Othenvise, it could be herbicides, it's one of the cornerstones if you can operate a cat or similar bumped and fail to catch the mountain of an integrated mountain beaver tracked machine, you may want to beaver when the jaws snap shut. program. pile the slash. Figure 4.-Conibear traps are inexpensive and generally available at local hardware Stores. They can also be ordered through forestry and reforestation supply houses. Each trap weighs about 1 pound. Replace- rnent triggers, springs, and Special safety Setters are also available. Figure 5.-Typical runway Set for the Conibear #I 10 trap.

To secure the trap, place one stick Examine each trap. Leave any traps You can contract trapping to between the spring bars next to the not sprung. Reset sprung traps in the professionals if you don't have the jaws and another stick through the same location. When you make a time or the ability to do it yourself. ring at the end of the spring bar successful catch, reset and trap again. Contract trapping costs range from (figure 5). If you set a trap Wait 2 to 3 days and nights before $15 to $50 per acre. aboveground in front of an exit hole, returning for your final check. It's best to trap reforestation areas you'll catch nontarget animals You should relocate traps after this before you plant seedlings. If logging (skunks, rabbits, or weasels) more check if you didn't catch any ani- is completed by late summer or early often than mountain beaver. mals-remember, mountain beavers fall and site preparation by late Predators (coyotes, foxes, bears, are solitary. If you have a high October, you'll have 2 to 3 months to bobcats) will find the trapped animals percentage of successful traps (greater trap before tree planting. and pul1 them out of the runways. If than 10%), keep your traps on the site Trapping is often conducted after you don't secure the trap, the predator for 2 to 3 more days. sites have been burned for site will leave with the animal und the Maintaining equipment is an preparation. These plantations will be trap. Secure the trap by wiring the important part of a successful trapping relatively clean and easily trapped; trap chain to a log or sapling. program. Trappers often take newly you can use fresh kickouts to locate Successful trapping requires close purchased traps and leave them mountain beaver that survive the fire. monitoring and good record keeping. outside to weather for several days Be cautious when you use traps If you're setting only a few traps in a before using them. Mountain beavers close to residences or in areas that nearby, accessible area, it's easy to have a keen sense of smell: Some- people frequently use. There's some check traps every day. On larger times, the scent of new meta1 or oil on risk of exposure to children and projects, you'll need a schedule for traps will be enough to cause them to domesticpets and smaller animals. In monitoring. Professional trappers avoid the trap. some cases, it may be more advisable check traps every 3 days. Never oil traps. If you need a to use a live trap (figure 6) even Marking trap locations and keeping lubricant, put traps in a pot of boiling though they're substantially more accurate records of successful trap water with either western hemlock or costly. locations will prevent unnecessary western redcedar branches and retrapping of areas you've already foliage. The coniferous plant materi- Tubing. You can place rigid Vexar covered. Use flagging to mark and als will provide a natural lubricant to tubes (figure 7) over planted seedlings number trap locations. traps. to protect individual trees from mountain beaver damage. These success rate in tests in the Oregon Coast and Cascade ranges, and its continued EPA registration is subject to collecting more data on its effec- tiveness. Place two or three Boomer-rid pellets at least 2 feet down each tunnel, to keep them out of reach of deer, elk, and other nontarget animals. You'll get the best results if you treat every active runway and burrow Figure 6.-The Havahart live trap is considerably more expensive than the Conibear, but it system. Mountain beaver gather the can be used to capture small to medium-sized animals such as groundhogs, skunks, and pellets and eat or store them for later mountain beaver in inhabited areas. You can buy it with either single or double entrances. use. Strychnine is a highly toxic poison, and swallowing only one or two pellets will kill most mountain beaver. plastic-meshed tubes are photodegrad- to stake them so they won't fall or be Bait will maintain its effectiveness for able; they'll break down after 2 to 4 pushed over. To save cost, trapping is 2 to 3 weeks if it's underground, out years, eliminating the extra cost of ofien combined with tubing only a of the rain. removal. portion of the trees. Baiting is most effective on freshly They provide good protection from This is especially effective when burned or cleared sites where little rabbits, deer, and elk, and initial you plant seedlings in mountain alternative food is available. One protection from mountain beaver. beaver habitat near draws, debris pound treats 1 to 2 acres. However, mountain beaver will climb piles, or brushy concentrations that Small animals (chipmunks, the tubes and clip laterals and leaders remain after site preparation. Because squirrels, rabbits, skunks, mice, and as they emerge. trapping may not remove every voles) use mountain beaver burrows Vexar tubes are expensive, and mountain beaver present in an area, on a secondary basis. It's likely that installation is labor-intensive. In areas tubing seedlings in draws or next to they'll be exposed to baits used to of heavy snow over 1 foot, and if you slash piles can provide an added level poison mountain beavers; however, use 24- or 36-inch tubes, you'll need of protection. there's no way to prevent them from In areas that received good site contact. preparation, upslope locations and You'll minimize hazard to nontarget Open sections that have low concen- species if you take care to bait active trations of mountain beavers may tunnels only, using only two or three warrant trapping only, without going pellets. This way, mountain beavers the cost of tubing every seedling. should carry them away before other wildlife find them. Poisoning. In the past, forest managers have tested a variety of Repellants. Unfortunately, there techniques and chernicals to control are no repellents effective against mountain beaver. Strychnine was used mountain beaver damage. on various baits, including native foods like swordfern. A number of other poisons were tested and ruled out, including a toxic tracking foam that mountain beavers would ingest Use pesticides safely! by licking their fur. Wear protective clothing and These methods were ruled out for safety devices as recornrnended on various reasons, and they're not the label. Bathe or shower after available for use today. each use. Only a pelleted strychnine bait Read the pesticide label-even if called Boomer-rid is available for use you've used the pesticide before. today. These strychnine-impregnated Foiiow closely the instructions on alfalfa pellets, about 1!h inches long, the label (and any other directions are treated with a weatherability agent you have). to maintain form and attractiveness Be cautious when you apply pesti- for several weeks when placed cides. Know your legal responsi- underground. bility as a pesticide applicator. You Figure 7.-Vexar tubing is available in a Warning: Boomer-rid is a restricted may be liable for injury or damage variety of heights, ranging from 18 to 36 inches. Stake them to secure them in an use pesticide that can be applied only resulting from pesticide use. upright position. Tilted tubes increase the by a licensed, certzjiedpesticide risk of terminal deformation. applicator: It has had about 50% and recoid keeping as burning, mechanical clearing, or Black, H.C., E.J. Dimock, and J. herbicides, as appropriate, to Rochelle Evans, Anima1 Damage to To determine how effective your eliminate mountain beaver habitat control program is, periodically check Conijerous Forests in Oregon and and foods. Washington: A Survq 1963-1975, plantations for recurring damage. 4. Plan the timing of your harvesting Trapping requires regular inspection Research Bulletin 25, Forest and site preparation so that you can Research Lab, Oregon State and relocation of traps to ensure trap or bait before and immediately success. University. Single copies are after planting. available at no cost from: Publica- Tubing requires maintenance. 5. Plan far enough ahead so that you Check to ensure that: tions, College of Forestry, Oregon can use appropriately large seed- State University, Peavy Hall 154, tubes are in place, lings. Acquiring transplant stock Corvallis, OR 9733 1-5704. seedlings are capable of escaping may require planning 1 to 2 years ahead. Campbell, D.L., and J. Evans, Recent as they grow, and Approaches to Controlling Moun- seedlings aren't being distorted by 6. Combine lethal control measures tain Beavers in PaciJic Northwest the tube. (trapping or baiting) with seedling protection (Vexar tubes). Forests: Proceedings of Vertibrate Monitor poison baiting to deter- 7. Conduct followup checks and Pest Conference, U.C. Davis, 1988. mine whether baits are being removed control until seedlings become Single reprint copies are available and if fresh sign of mountain beaver established and large enough to be at no cost from: USDA-APHIS, activity is ceasing (the bait is work- out of danger. S&T, 3625 - 93rdAve. SW, ing). Olympia WA 98502. Keep good records. When you're applying control techniques in several locations, it's easy to lose track of when and where you applied controls. You can easily keep field records if you use some kind of marking system. For instance, use colored flagging to denote individual trap locations. You could use different colors for different trapping dates. Keeping records will help you track success and failure rates and identiSi places where you may need to change your technique or control measure. EmENSION SERVICE Summary You can best achieve successful management of mountain beaver damage in your forest plantations by an integrated approach that combines Trade-naine products and services are mentioned as illustrations only. This does not seedling protection, lethal control, and inean that the Oregon State University Extension Service either endorses these products silvicultural practices. and services or intends to discriininate against products and services not inentioned. Include these steps: The Woodland Wovkhook is a collection of publications prepared by the Oregon State 1. Properly identiSi mountain beaver University Extension Service specifically for owners and managers of private, nonin- as the actual pest causing the dustrial woodlands. The Wovkbook is organized into 11 sections, containing inforination damage. of long-range and day-to-day value for anyone interested in wise management, 2. Anticipate future problems by conservation, and use of woodland properties. It's available in a three-ring binder with recognizing good mountain beaver tabbed dividers for each section. habitat or the presence of high For information about how to order, and for a current list of titles and prices, inquire at populations. the office of the OSU Extension Service that serves your county. Extension Service, Oregon State University, Corvallis, O.E. Smith, director. This publication was produced and distributed in furtherance of the Acts of Congress of May 8 and June 30,1914. Extension work is a cooperative prograin of Oregon State Univer- sity, the U. S. Departinent of Agriculture, and Oregon counties. Oregon State University Extension Service offers educational programs, activities, and inaterials-without vegavd to vace, colov, national ovigin, sex, age, ov disahiliw-as required by Title V1 of the Civil Rights Act of 1964, Title IX of the Education Amend- ments of 1972, and Section 504 of the Rehabilitation Act of 1973. Oregon State University Extension Service is an Equal Opportunity Einployer.