Experiments with fences of this kind were made to determine their effectiveness and to seek possible improvements in their construction, with the result that one important change was made. Copperheads and small rattlesnakes could not get over the vertically-straight fence, but a six-foot rattlesnake used in the experiment was able to climb over it. When the same fence was tilted outward at a 30-degree angle, not even the largest snake was able to reach the top. Although such fences are expensive and difficult to keep in good repair, they may be desirable under some circumstances. A less costly method of keeping snakes away from residential property has been proposed by the manufacturers of a new chemical that allegedly repels and kills snakes. The product, a granular material with a civet musk odor, is reported by its distributors to kill a snake less than two feet in length if it is exposed longer than 20 seconds. Preliminary tests made at the Houston Zoo indicate that, in spite of claims to the contrary, the material had little effect on the snakes used. Each of more than a dozen different specimens, including examples of all the local poisonous kinds, unhesitatingly crawled through a wide barrier of the repellent that was poured on the ground. In some instances, the snake’s tongue contacted the granules, but none of the test reptiles showed any ill effects from exposure to the chemical. While these crude tests are certainly not conclusive, it would seem advisable to use commercial repellents with some reservations until they can be proved effective. Meanwhile, we can still prevent most snake bites by observing a few simple safe practices. PROTECTION IN THE FIELD In the field, where poisonous snakes are more common, they present a greater hazard to human life; consequently, campers, crop farmers and others who spend a great deal of time outdoors should necessarily take more care in avoiding snake bites. Because almost all snake bites are inflicted on the arms or legs of the victim, these limbs require special protection. The use of a little caution, when placing hands or feet where snakes may be partially or completely hidden from view, is the best protection you can give them. This is particularly true when climbing hand-over-hand on rocky ledges, where your hands reach the level of the ledge before your eyes do. Rattlesnakes and copperheads are partial to such rocky hillsides and here, especially during the warm days of early spring, they prefer to coil and sun themselves. [Illustration: Thoughtless reach] Armadillo and pack rat burrows also make excellent shelters for rattlesnakes, and only a reckless person would find an excuse to reach into one of these holes. Yet one year, in South Texas alone, at least two snake bites occurred when the victims, each in search of small game, reached into armadillo holes and were bitten by rattlesnakes coiled there.