Guillotine trap.—For general use the improved modern traps with a wire fall released by a baited trigger and driven by a coiled spring have marked advantages over the old forms, and many of them may be used at the same time. These traps, sometimes called "guillotine" traps, are of many designs, but the more simply constructed are preferable. Probably those made entirely of metal are the best, as they are more durable. Traps with tin or sheet-metal bases are not recommended.
Guillotine traps of the type shown in figure 5 should be baited with small pieces of Vienna sausage (Wienerwurst) or fried bacon. A small section of an ear of corn is an excellent bait if other grain is not present. The trigger wire should be bent inward to bring the bait into proper position for the fall to strike the rat in the neck, as shown in figure 6.
Other excellent baits for rats and mice are oatmeal, toasted cheese, toasted bread (buttered), fish, fish offal, fresh liver, raw meat, pine nuts, apples, carrots, and corn, and sunflower, squash, or pumpkin seeds. Broken fresh eggs are good bait at all seasons, and ripe tomatoes, green cucumbers, and other fresh vegetables are very tempting to the animals in winter. When seed, grain, or meal is used with a guillotine trap, it is put on the trigger plate, or the trigger wire may be bent outward and the bait placed directly under it.
Oatmeal (rolled oats) is recommended as a bait for guillotine traps made with wooden base and trigger plate (fig. 7). These traps are especially convenient to use on ledges or other narrow rat runs or at the openings of rat burrows. They are often used without bait.
A common mistake in trapping for rats and mice is to use only one or two traps when dozens are needed. For a large establishment hundreds of traps may be used to advantage, and a dozen is none too many for an ordinary barn or dwelling infested with rats. House mice are less suspicious than rats and are much more easily trapped. Small guillotine traps baited with oatmeal will soon rid an ordinary dwelling of the smaller pests.
Fig. 7.—Guillotine trap with wooden base and trigger plate.
Cage trap.—When rats are abundant, the large French wire cage traps may be used to advantage. They should be made of stiff wire, well reinforced. Many of those sold in stores are useless, because a full-grown rat can bend the light wires apart and so escape.
Cage traps may be baited and left open for several nights until the rats are accustomed to enter them to obtain food. They should then be closed and freshly baited, when a larger catch may be expected, especially of young rats (fig. 8). As many as 25, and even more, partly grown rats have been taken at a time in one of these traps. It is better to cover the trap than to leave it exposed. A short board should be laid on the trap and an old cloth or bag or a bunch of hay or straw thrown carelessly over the top. Often the trap may be placed with the entrance opposite a rat hole and fitting it so closely that rats can not pass through without entering the trap. If a single rat is caught it may be left in the trap as a decoy to others.