Mousetrap

A mousetrap is a specialised type of animal trap designed primarily to catch mice; however, it may also (intentionally or unintentionally) trap other small animals. Mousetraps are usually set in an indoor location where there is a suspected infestation of rodents. Larger traps are designed to catch other species of animals; such as rats, squirrels, other small rodents, or other animals.

The trap that is credited as the first patented lethal mousetrap was a set of spring-loaded, cast-iron jaws dubbed "Royal No. 1". It was patented on 4 November 1879 by James M. Keep of New York, US patent 221,320. From the patent description, it is clear that this is not the first mousetrap of this type, but the patent is for this simplified, easy to manufacture, design. It is the industrial age development of the deadfall trap, but relying on the force of a wound spring rather than gravity.

The jaws of this type are operated by a coiled spring and the triggering mechanism is between the jaws, where the bait is held. The snaps the jaws shut, killing the rodent.

Lightweight traps of this style are now constructed from plastic. These traps do not have a powerful snap like other types. They are safer for the fingers of the person setting them than other lethal traps, and can be set with the press on a tab by a single finger or even by foot.

The classic spring-loaded mousetrap was first patented by William C. Hooker of Abingdon, Illinois, who received US patent 528671 for his design in 1894. A British inventor, James Henry Atkinson, patented a similar trap called the "Little Nipper" in 1898, including variations that had a weight-activated treadle as the trip.

In 1899, Atkinson patented a modification of his earlier design that transformed it from a trap that goes off by a step on the treadle into one that goes off by a pull on the bait. The similarity of the latter design with Hooker's of 1894 may have contributed to a common mistake of giving priority to Atkinson.

It is a simple device with a heavily spring-loaded bar and a trip to release it. Cheese may be placed on the trip as bait, but other food such as oats, chocolate, bread, meat, butter and peanut butter are more commonly used. The spring-loaded bar swings down rapidly and with great force when anything, usually a mouse, touches the trip. The design is such that the mouse's neck or spinal cord will be broken, or its ribs or skull crushed, by the force of the bar. The trap can be held over a bin and the dead mouse released into it by pulling the bar. In the case of rats, which are much larger than mice, a much larger version of the same type of trap is used to kill them. Some spring mousetraps have a plastic extended trip. The larger trip has two notable differences over the smaller traditional type: increased leverage, which requires less force from the rodent to trip it; and the larger surface area of the trip increases the probability that even the most cunning of rodents will set off the trap. The exact latching mechanism holding the trip varies a lot and some need to be set right at the edge in order to be sensitive enough to catch cautious mice.

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