Partly ripened heads of barley or wheat soaked in a solution of strychnine and saccharine or coated with the starch-strychnine solution just described have also proved effective baits for rabbits, but great care must be exercised in using them, as they are likely to be eaten by live stock.
Cottontail rabbits may be poisoned in winter by baiting them with twigs cut from apple trees and dipped in or thinly coated with the starch-strychnine poison. These twigs are scattered along rabbit trails and are effective against both meadow mice and rabbits. They are less dangerous to domestic animals than grain baits.
BACTERIAL DISEASES.
The fact that when rabbits become excessively abundant in any locality epizootic diseases often destroy them in large numbers has led many people to expect that a micro-organism would be found which would afford a ready means of rabbit control. The Biological Survey receives many applications for such bacterial preparations. In reply to all of them it has been necessary to state that thus far all attempts to spread contagious disease artificially among wild rabbits have failed to give practical results.
PROTECTION OF CROPS FROM RABBITS.
Complete extermination of rabbits in any part of the United States is not desirable, even if possible. They should be reduced in numbers only sufficiently to secure comparative safety to crops, and before active wholesale destruction of the animals is attempted the possibility of crop protection by other means should be carefully considered. In many cases one of these means would probably be the more economical method.
RABBIT-PROOF FENCES.
When rabbits are abundant and the area to be protected is not too great, a rabbit-proof fence may profitably be used. Woven-wire netting is recommended for this purpose. This material is in general use, not only against the rabbit pests of Australia and Europe, but in our own country against both large and small rabbits. As our species burrow less than the European rabbit the requirements for rabbit proofing a fence here are not so great. Even the cottontails, when driven by hunger, will dig under a fence, but this may be prevented either by use of wire with close barbs in contact with the ground or by plowing a furrow against the lower edge. A netting of galvanized wire with 1-1/2-inch mesh and 2-1/2 to 3 feet high is a sufficient barrier against cottontails. Where snow is infrequent market gardeners and nurserymen use a 2-foot fence, but in the North they prefer to use a netting 3-1/2 feet wide, and to turn from 4 to 6 inches of the lower edge flat and cover it with soil. Netting made of No. 20 wire costs from 25 to 35 cents a rod. Heavier netting slightly increases the cost, but adds to the durability of the fence. Where lumber is cheap, a picket fence or one made of laths and wire is practicable. When deep snows fall and drifts form, fences offer no protection to crops against rabbits.