A 3-inch-diameter plastic tube mounted on a truck was designed for distributing bait (cut carrots or grain) for mammal control. Baits are fed into the tube by an operator standing in the truck bed. The device is light-weight and detachable and permits rapid, accurate placement of bait along a line on the ground or in a plowed furrow.

Since 1963, biologists of the Denver Wildlife Research Center have been investigating methods of alleviating agricultural damage by the black-tailed jackrabbit (Lepus californicus). Of the several approaches to control, most biological methods (predation, habitat manipulation, disease and parasites, and chemosterilants) appear impractical with present knowledge. Mechanical control except for fence barriers, usually has limited effectiveness. Currently, the most useful approach is still chemical control. Improved baiting techniques and several chemical control agents, including an experimental toxicant highly selective for jackrabbits, are described.

The toxic sheep collar is the most selective method known for killing coyotes that prey on domestic sheep. The concept dates back to the early 1900's and has been studied at the Denver Wildlife Research Center (DWRC) since 1974. Field tests with sodium cyanide (NaCN) in 1975 were unsuccessful due to repellent properties of the toxicant and to the apparent reluctance of coyotes to attack tethered lambs wearing bulky collars. Coyotes attacked one or more tethered, collared lambs in 7 of the 19 test pastures. In all, 14 collared lambs were attacked. Eight of the collars were punctured but no dead coyotes were recovered. A smaller collar containing diphacinone was field tested in 1976. The diphacinone-filled collars were readily accepted by coyotes and lethal to them, but the slow action (5-16 days between dosing and death) of diphacinone made it difficult to assess the effectiveness of these collars under field conditions. Target flocks containing 1 to 12 collared lambs plus uncollared ewes were placed in 15 fenced pastures from which the larger ranch flocks had been removed after repeated coyote predation. One or more collared lambs were attacked in 11 of the 15 tests. An unknown number of coyotes were killed, and in most tests the subsequent incidence of predation was lower than that before the test. Captive coyotes continued to kill sheep for 4 or 5 days after they received a lethal dose of diphacinone; therefore a faster-acting toxicant is needed. This research has shown that problem coyotes can be killed with toxic collars, but further studies are needed to determine the feasibility of this approach compared with traditional means of control. In most tests to date the frequency of coyote predation has been too low and too irregular to permit effective use of the collar; target flocks were in the field for an average of 10 days before being attacked. The known disadvantages of the method include the need to sacrifice live lambs, the human hazards associated with the use of toxicants under field conditions, and the costs of managing target flocks and other sheep in the problem areas.

Since 1974 the Fish and Wildlife Service has studied a "toxic collar" to poison coyotes that attack collared sheep and goats. The collar patent (McBride 1974) indicates that the same collar could deliver chemicals to repel coyotes, thus saving both the coyote and the livestock. This report summarizes our experience with nonlethal tests of collars. During collar tests with 10 different toxicants, 21 coyotes received sublethal doses followed by aversive behavior or potentially aversive reactions. The subsequent predation history of these coyotes was examined for prey-avoidance. After a sublethal test, all coyotes killed lambs or kids in about 40 days, and 20 of 21 were eventually killed by another toxic collar. Limited testing with coyotes averted to salt flavor by lithium chloride-treated sheep bait also indicated poor protection of live sheep treated externally with salts (NaCl and LiCl). The results indicated little potential for using repellent or aversive chemicals in toxic collars or on sheep to repel coyotes.

The use of LiCl-treated baits and carcasses has been advocated as a means of controlling coyote predation on sheep through a process known as "aversive conditioning or taste aversion." While some investigators have made well publicized claims of damage reduction through the use of LiCl on sheep ranges, other researchers have experienced difficulty establishing prey aversion in captive coyotes. The conflicting results suggest a need for extensive, carefully controlled research in both pen and field situations before valid conclusions can be reached regarding aversive conditioning as a depredations control method.