Rodents play a significant role in the transmission of many diseases
Rodenticides are an efficient means of rodent control, but many people are reluctant to use poisonous chemicals around the home, especially in the presence of children and pets.
There are a number of alternative methods of control but you still need a measure of care and competence to obtain the most effective results.
None of the methods are without risks or guaranteed to get results, as this depends on using the methods appropriately.
Both live and dead rodents can spread infectious diseases and parasites. In addition, it is essential with every method chosen to back it up with prevention measures to deny rats and mice food and access to shelter, making sure they cannot return.
In choosing a rodent control method you should consider:
Rodent traps usually require the use of food bait to attract the rodents. They have poor eyesight but a highly developed sense of taste and smell to locate food. Rats and mice need fresh food, preferably with an odor that will attract them close enough to be caught.
They prefer cereal grains, meat, fish, nuts, and will also eat many manufactured foods such as peanut butter, chocolate, fruit jelly and cheese (although this is not the staple food that cartoons would have us believe).
Rats will initially avoid anything new placed in their environment and then investigate it cautiously. This ‘fear of the new’ or neophobia can take a few days to overcome. For all rodents if there is an adverse experience the shyness can last for weeks or months. With food bait they may eat small amounts at first to test the flavor and any reaction, before accepting it.
Placing traps with food, but not setting the trigger for a while, will help rats and mice to overcome any trap and bait shyness.
Traps that are designed to kill rodents with a spring release need to be used with some skill to position correctly and avoid affecting other wildlife, pets and children.
Traps have advantages over rodenticides for small infestations in small structures, such as homes and garages. Their advantages are:
The trap should be placed in a rat or mouse run, usually along a wall, behind objects such as fridges or cupboards.
Place the trigger side flush against the wall, or use two with the triggers facing away from each other. You may need to place them in several sites to target the pest population effectively and quickly. If you can place across a route you know rodents are using regularly you may not even need to use bait — as they scurry along they will simply ‘blunder’ into the traps!
The traps must be checked frequently to remove dead animals. Also, they do not always kill cleanly, so you must check them regularly to kill any trapped live animal humanely.
If used outdoors they should be placed in natural or artificial tunnels to target the rodent pest and protect the bait from rain and non-target animals and children.
These have a spring or electronic release catch that closes the door on a cage or container when an animal triggers the mechanism. As with the spring traps, the animals are lured by the smell of food, so fresh, wholesome food needs to be placed on the trigger mechanism and renewed when it deteriorates.
In many countries a captured animal is subject to animal welfare legislation making it an offence to cause unnecessary suffering. Therefore the traps need to be checked frequently (morning and evening) to release any non-target animals caught. It may be illegal to relocate and release rodent pests, therefore if you use the traps you need to know how to kill the animal humanely, or arrange for an expert to do it – the product you are using should advise you of relevant local legislation.
These are enclosed traps that detect an animal entering, shut the entrances and send a high-voltage electric charge through some metal plates on the floor of the container to kill the rat or mouse. The metal plates need to be kept clean to ensure an adequate charge is discharged through the rodent. These traps are expensive and not all can be used outdoors because they use mains voltage or lack protection of the components from rain and damp.
As with other traps you may need several and they need to be checked frequently to check for and dispose of any dead animals. Manufacturers claim advantages of this method are a clean kill and easy disposal without handling the animal, but similar non-target rodents would still be killed by such a device.
These are available in some countries, but are considered inhumane by some experts. They are boards of varying sizes covered with very sticky glue, often mixed with food flavoring, designed to immobilize an animal that walks on them. They are indiscriminate and can trap other animals, including pets, snakes (some are sold specifically to catch snakes), birds and bats, so need to be checked regularly.
The animal is not killed by the trap, which means that when you catch a pest rodent you need to know how to kill the trapped animal humanely. Animals suffer pain and stress and can harm themselves while trying to get free from the glue. They can cover themselves in their own urine and feces while panicking and struggling to get free. If left, the animal will suffer from dehydration, starvation and exhaustion, dying within 3-5 days.
There is also a danger to you in handling the live animal: from being bitten by the frightened, uncontained animal; and contamination from its urine and feces on the animal, the board and the surrounding area.
The Humane Society of America says: “Glue boards are responsible for more suffering than virtually any other wildlife control product on the market. Most animals caught in glue boards suffer slow and agonizing deaths.”
Technology can provide the proverbial ‘better mouse trap’. Ehrlich Pest Control has developed the RADAR mouse trap to control mice in a humane manner. A box-shaped container has an entrance at each end for the mouse to enter. When the mouse passes infrared detectors it triggers the doors to close, sealing the container. Carbon dioxide is automatically released to kill the mouse quickly and humanely and keep it isolated to remove any danger of contamination.
A warning light on the outside of the unit shows that a mouse has been caught and an automated signal can be passed through a radio network and the internet to record the capture and signal to a service technician that the unit needs attention.
It is designed for use in businesses where a high degree of hygiene and pest control is essential and detailed records of pest control measures are needed for legislative requirements.
Rats and mice can hear and communicate using ultrasound frequencies higher than the hearing range of humans, dogs and cats:
It is claimed, therefore, that high volume ultrasound is able to repel rats and mice without affecting humans, cats and dogs. However, ultrasound dissipates quickly with distance and is blocked by objects, so the sound is unlikely to travel far in a large and complex space — such as a house. There is only some evidence that ultrasound has limited effect when used in very small spaces.
There are many electronic devices on the market that produce ultrasound specifically to repel rats and mice — and some claim to repel a whole menagerie of pests. Studies conducted since at least the 1970s, however, have repeatedly found that in controlled conditions ultrasound has little long-term effect on the behavior of rats and mice, as they get used to the sound. It may only have an effect for a few days and can depend on the ultrasonic frequencies used and their intensity.
In fact, rodents are easily frightened by any strange noises, but quickly become used to them, especially if nothing adverse happens while the noise occurs. This means it is essential to use standard rodent control and prevention methods and limit the use of ultrasound to a supporting role in deterring infestation.
Rodents can find some smells repellent, such as ammonia or moth balls, and folklore claims various plant scents repel them, but none are effective because, just like other repellents, the rodents quickly become used to them. Also, in many countries there are no products approved for use as a rodent repellent. There is no substitute for standard control and prevention measures!
Cats and dogs can catch rats and mice, and there is a long history of breeding dogs such as terriers for rodent control around farms and homes, mainly before the advent of poisons and trigger traps. The skeleton of a dog similar to a terrier (identified by DNA) was even found in the wreck Henry VIII’s warship, the Mary Rose, which sank on the south coast of England in 1545.
Cats and dogs are not efficient controllers of rodent populations in urban areas, however, as rats and mice can easily find places to hide from pets and learn to avoid them most of the time. Well-fed pets in the home environment will have little incentive to hunt and they will not be able to access many of the places the rats and mice frequent in a home. Rats and mice can even thrive in the presence of pets, living off their food, especially when they are kept outdoors!
Robert M Timm. Norway rats. The Handbook: Prevention and Control of Wildlife Damage. Paper 5. University of Nebraska – Lincoln. http://digitalcommons.unl.edu/icwdmhandbook/5
Rats. Integrated Pest Management Program, University of California Division of Agriculture and Natural Resources. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html
Rats: options for controlling infestations. Natural England Technical Information Note TIN057.
DeGomez T, Aflitto N. Sonic pest repellents. University of Arizona, College of Agriculture and Life Sciences, 2014. http://arizona.openrepository.com/arizona/bitstream/10150/333139/1/AZ1639-2014.pdf
The Humane Society of the United States. Scrap the Trap When Evicting Wildlife. http://www.humanesociety.org/animals/resources/tips/scrap_the_trap.html
How well do dogs and other animals hear? http://www.lsu.edu/deafness/HearingRange.html
The Mary Rose Museum. Identifying an old dog with new tricks. www.maryrose.org/identifying-the-mary-rose-dog