Mountain beavers are routinely kill trapped for damage control on many forest lands scheduled for planting. Trapping is usually done just prior to planting and repeated one or two years afterward. Trapping is also repeated when damage is found in established plantations. Set kill traps in older stands where stems and roots are being girdled and undermined. Live trapping is seldom done in forest lands except for research purposes, but it is used where there are urban damage problems.
Kill trapping is normally done using unbaited Conibear® No. 110 traps set in main burrows. Anchor traps with three sticks, with either two in the spring (see Fig. 10 in the online resource referenced below) or with one in the spring and one at the far end of the jaws, in a vertical position with the trigger hanging. The trap should take up most of the space in the burrow, and when properly anchored, is readily entered by the mountain beavers. This trap is sometimes not immediately lethal because of the mountain beaver’s thick short neck. Stronger double-spring traps may be more effective but are more difficult to set in the limited burrow space.
Teams of trappers are normally used when trapping large acreages. Individual trappers should be spaced about 30 to 50 feet (9.1 to 15.2 m) apart, depending on habitat conditions. Extra searching may be required in areas with many small drainages that may have many burrows. Active burrows have fresh soil and vegetation piled at burrow entrances or in burrows. Burrows can often be visually inspected through openings to determine if there is recent use. Set two or three traps in each active burrow system. All trap sites should be marked with flags and mapped so they may be relocated; a crew of trappers should use several colors of flagging so that individuals can relocate their own traplines by color.
Trapping in older stands of conifers can be very difficult because traps are not easily relocated when branches hide the flagging. Mapping and flagging travel routes in this type of habitat may be necessary. The traplines are usually checked after one day and again checked and pulled after about five days. Traps are usually reset during the first check even where mountain beavers are captured because the systems may be quickly invaded by other mountain beavers.
If trapping is unsuccessful, move traps to burrows with fresh activity. During the breeding season (January to March), male mountain beavers may be more commonly trapped than females because of their greater activity.
During subfreezing temperatures, trapping should be postponed or trapping periods lengthened to include warmer periods when mountain beavers are more active. Trapping during periods of snow is also usually less successful than during snow-free periods because trap sites are difficult to locate and set, and animals are less active.
Trapping may take nontarget species such as weasels, spotted skunks (Spilogale putorius), mink, squirrels (Tamiasciurus spp.), rabbits, and hares that use the mountain beaver burrows. Nontarget losses may be reduced by positioning the trap trigger near the side of the trap so that it is less likely to be tripped when small animals pass through.
Live trapping is recommended where domestic animals may enter the burrows. Double-door wire mesh live traps such as Tomahawk traps (6 x 6 x 24 inches [15 x 15 x 61 cm]) should be set nearly level in main burrows. Suitable vegetation should be placed inside and along the outside of the trap. Wrap the trap with black plastic, and cover it with soil to protect animals from the weather. Placement should assure that animals enter rather than go around the ends of the trap. Traps must be checked once or twice daily, preferably in early morning and again in the late afternoon, to minimize injury and stress to mountain beavers held in the live traps. Live-captured mountain beavers should be placed in dry burlap sacks and, if necessary, euthanized with carbon dioxide.
Resources: (online)
Mountain Beavers