What is the most humane way to kill pest rats and mice?

There are a range of different poisons and traps used in Australia for controlling rats and mice. The RSPCA is concerned that many of these methods are inhumane and involve a slow and painful death. The following information provides advice on how to minimise rats and mice establishing, and where control is necessary, the most humane methods available. [1, 2]

Live traps

The use of live traps is a popular choice for many people who prefer to avoid killing rats and mice but want to remove them from their home or property. However, the humaneness of live traps depends on how frequently the traps are checked, the design of the trap, and whether food, water or nesting material are provided to avoid starvation, dehydration or cold stress. Live traps must be designed to avoid injury during closure and when the animal is trapped inside. Before use the trap mechanism must be checked to ensure that it will not catch the tail or limbs of the animal when it closes.

Live traps must be inspected every morning and any trapped animals humanely killed or released into a suitable location. Animals must not be left to die slowly in the trap. Unfortunately, the available evidence suggests that the survival rate of relocated animals is often very low – releasing animals into a new location is therefore unlikely to be a more humane alternative to killing them quickly and painlessly. Another option is to transport the animal in the live trap safely and comfortably as soon as possible to the nearest veterinary clinic for humane killing. Prior to setting the trap, ascertain that the clinic can undertake this procedure.

Snap traps

A more humane and faster method than live trapping and killing is the use of a well-designed snap trap. These come in different sizes that can be used for either rats or mice. It is recommended to only use a reliable and well-designed trap which ensures that the animal’s head is fully inside the trap area when the trap is triggered and can be consistently set and reset. Snap traps that are designed well and used properly, are consistently found to ensure a quick death to the mouse or rat and once cleaned, they can be reused.

The following tips should help with setting traps effectively:

• The bait should only be placed within the marked bait area and keep the rest of the trap clean of any food matter. This will reduce the likelihood of the trap closing and injuring, rather than killing the animal. Baits may include either peanut butter, dried fruit or bread, which should be fresh. If traps aren’t being triggered, then changing the type of bait may create interest.
• For best effect, traps should be placed parallel to (not at right angles) and in contact with a wall or other solid object and in a place that encourages the rodent to use a path to the trap. It is recommended to place the trap inside a ‘tunnel’ or at the end of a ‘funnel’, which can be created with appropriate sturdy materials, to help guide the rodent into the trap.

After setting at night, all traps must be checked every morning and trapped animals checked to ensure they are dead. If any animals are trapped and injured, they must be humanely killed (with a rapid, heavy blow to the head). Traps that have failed should be discarded and replaced by another design or brand of snap trap. It is important to use an effective and reliable snap trap that kills the animal instantly.

The RSPCA is opposed to the use of glue boards as they cause severe suffering.

Other control methods

Where there is a large scale rodent problem, the RSPCA recommends that only methods resulting in a quick and humane death are used. Many people use a toxic bait to kill unwanted pests. People often choose toxic baits as the poisoned rodent will rarely be seen as it wanders off to die. These baits contain chemicals, called anticoagulants, which cause the rodent to die slowly and painfully from internal bleeding. These poisons are not considered to be humane due to their toxic effects including difficulty breathing, weakness, vomiting, bleeding gums, seizures, abdominal swelling and pain. In addition, the body of the poisoned rodent presents a significant risk if it is eaten by other animals, including native wildlife. A recent Australian study showed that over 70% of dead and dying boobook owls sampled had been exposed to rodent anticoagulants and that over 50% had dangerously high levels [3].

Rodent proofing properties

Houses that are located close to bush or parkland or other open spaces are prone to mouse invasion. In older buildings, where there may be cracks or loose bricks, problems with rats and mice are also common. The following precautions, which are easy and inexpensive, will reduce the likelihood of rats and mice entering houses or sheds.

• In cupboards and the pantry, opened food should be stored in metal, glass or heavy duty plastic containers with tight lids.
• Uneaten pet food should be discarded or if still fresh, stored it in a secure container.
• All food remains, litter and other rubbish inside and outside the home should be swept up and discarded in secure bins.
• All rubbish should be placed in metal or heavy plastic bins with tight lids.
• Rubbish should be placed outside on the morning that it is to be collected; rubbish bags or bins should never be left on the footpath overnight.
• Weeds and debris near buildings and in yards should be removed to minimise hiding places.
• All windows should have intact screens.
• Outside doors should be kept closed and metal trim used to prevent rodents from gnawing and entering underneath.
• Areas should be checked to ensure all holes are sealed, including the basement and garage.
• Materials such as firewood or garden supplies should be stored on raised platforms with an open area underneath to minimise rodent hiding places and all unused materials and junk should be removed.