The Pest Advice

I have recently completed a series of videos describing how to identify rodent infestations, what products to use to get rid of rats and mice, how to use those products, safe use of and disposal of rodenticides and how to prevent rodent infestations.

ANZAC day tomorrow! Let’s hope the weather remains good. We have been having something of an Indian summer this autumn and this has meant ongoing, or even increased, problems for some people with insect pests.

The weather has been warm during the day but clear skies at night have meant low temperatures and even a frost this morning in the fields around my home. This time of the year is normally when rats and mice move indoors to find fresh sources of food and shelter from the cold. Perhaps a good use of your time would be to take 30 minutes of your ANZAC day off and look around your home for places that rats and mice could enter.

It is almost impossible to make any building 100% proofed against rats and mice but 95% makes having an infestation 20 times less likely. Setting out some rodenticide baits and traps would add to the protection; controlling any rodents that find their way in.

What do you get if you try to cross a rat with a skunk?
Dirty looks from the rat! 

1. Deny rodents entry – Go outside and examine your buildings for possible entry points. A mouse can squeeze beneath a door if there is a gap large enough to fit a pencil a young rat is only a little larger than a mouse! Draft excluding brush strips, are an ideal method of proofing such gaps. You might also consider placing some rodenticide around the exterior of the house to reduce the numbers that might find their way in.
2. Deny rodents food – Take 10 minutes to look around your kitchen and check that should a mouse or rat get in that there is no food behind the fridge, or spilled down the side of the cooker. Check that dried good such as cereals are in sealed, preferably metal, containers. Make sure butter and even bars of soap are out of the reach of rodents. Remember, rats and mice are excellent climbers and just putting food high on a shelf may not be out of their reach.
3. Be ready for rodent entry – No matter how carefully you find and seal possible entry points if you can get into a building through and open door so can a rat or mouse. They may also get in carried in a box of goods and there are almost always other possible entry points around any building. So it is always wise to keep fresh rodenticide bait in place in safe places such as the roof void so that any rodents that get in are dealt with before you know about them.
1. Put bait in safe places NOW. Don’t wait for signs of their entry. Place the bait where rodents might encounter it but where pets and children cannot. Set traps as well.
2. Rodenticide baits are more effective than traps but once a rodent has taken some bait it is more likely to get caught in a trap and body can then be removed.
3. Particularly if dealing with roof rats block baits should be fixed in place so that the rats cannot take it away and store it. Some baits have holes so that they can be nailed in place in voids and fixed by use of a wire. Block baits without holes can be put in a plastic bag and the bag fixed in place.

Rodent droppings and urine can carry serious disease

Zoonoses are diseases caught from animals. Wild rats and mice carry several diseases that can be passed on to humans. The most famous epidemic caused by close association of rats with people is the Black Death which caused the death of millions in 14th century Europe. The disease was the plague caused by the bacterium Yersinia pestis. 


Plague


Plague still infects and kills people world wide but thankfully not in New Zealand. But there are other serious diseases that can be caught from wild (and pet) rodents in New Zealand.

In April I predicted that rodents would be a problem of larger than normal proportions this winter, particularly in quake damaged Christchurch. See here.

Rats Surviving Outside This Winter

I am happy to say that this prediction has not come to pass yet. Rats and mice have been able to survive outside due to the mild weather that New Zealand has experienced so far this winter. While many rats and mice have invaded homes in search of food and shelter, this has, so far, been in the normal range and not been a plague.

The unseasonably mild weather has had implications for ski fields and the lack of snow has meant resorts like Queenstown have not been able to start the ski season leaving many ski field employees without work and skiers seeking alternative entertainment.

For animals in the wild it has meant that more food is available to them and less food is needed to keep warm. The result is a high survival rate but less movement of rodent pests indoors. However, if a cold snap does come along there is still a likelihood that rodents will move indoors to escape the cold. So it is important to be proactive and be prepared.

What did the lab rat say his mate?
"I've got my scientist so well trained that every time I ring the bell, she brings me a snack."

This week I have received several queries from people asking whether it is necessary to place water out with rodent baits. They have been told, or have read, that poison baits make rats and mice thirsty and that they will gnaw pipes to get at water to drink; so that placing water with the bait means they are less likely to gnaw pipes.

This is one of those stories that has some truth and sounds plausible but but comes to the wrong conclusions.

Damage to cables from gnawing rats

Almost all rodent baits contain an anti-coagulant toxin* such as the coumatetralyl used in NO Rats & Mice. Anti-coagulants do indeed have a slight tendency to make the rats and mice thirsty, but the rodents are likely to find water in their usual places if they are able.

Rodents do indeed often gnaw at pipework and cables causing considerable damage. But they do this because their incisor (front) teeth grow continually throughout their life and must be kept worn down and sharp by regular gnawing. This is why rats and mice gnaw things other than their food. Plastics, including plastic pipes and cable covering, seem to be of a consistency that they get ‘pleasure’ from gnawing.

Placing water alongside baits is unlikely to influence the likelihood of them gnawing pipes. Anti-coagulant poisons take several days to begin to take effect. So the rats and mice are likely to be some other place when they begin to feel ill and thirsty. In most cases they fall ill and die in their nest.

The delayed action of anti-coagulants is very important for their effectiveness and in making anti-coagulants a safe type of poison for use in homes.

If a poison makes a rat or mouse feel ill quickly, they will associate the illness with the bait and will avoid eating any more. If they have not yet consumed a lethal dose they can recover and will be ‘bait shy’ meaning baits will no longer be effective. With ant-coagulants the delayed onset of illness means they do not associate the illness with the bait and they have already taken several feeds of bait ensuring they have taken a lethal dose from which there is no recovery.

The slow onset of illness also has the advantage of giving plenty of time to administer the antidote to any non-target animal, such as a pet,  that accidentally takes bait. Vitamin K is a fast and effective antidote for anti-coagulant poisoning.

Another interesting fact about mice is that they can obtain all their water from their food and may live their lives without ever needing a drink.

In conclusion, there is no need to leave water out with rat and mouse bait. But it is important to control rats and mice promptly to reduce the risk of damage to pipes and cables caused by their gnawing habits.


*Kiwicare Natural NO Rats is a novel rodent bait that does not contain an anti-coagulant poison. It does not contain any poison! Instead it works by physical action. Rodents do not posses the enzymes in their gut necessary to break down the cellulose in the bait. Rodents cannot vomit and so the bait remains in the alimentary canal where it prevents feeding and causes dehydration and death by heart attack. The bait is safe for other animals.

Who is the king rat in Rome?
Julius Cheeser.

Easter is traditionally a time when DIY enthusiasts get down to preparing the home and garden for the coming winter months. The hardware stores and garden centres will be doing a good trade this long weekend.

It is noticeable that sales of Kiwicare products for the control of insects of all sorts have surged in the last month; this is one or two months later than traditionally.

Our retailers such Mitre10, Bunning’s, Placemakers and Hammer have stocked up early for rodent control products. It has been noticeable that rodenticides have sold well throughout the spring and summer and this suggests to me that it has been a ‘bumper’ year for breeding of rodents. The result is likely to be a big influx of rats and mice to homes, offices, factories and farms when some real cool weather arrives. It is advisable to be pro-active and carry out a simple preventative plan now. I recently wrote a guide for the Yellow Pages on how to keep rats and mice out. You can check it out here.

In the garden and outside the house it is a good time to tidy up and prepare the lawn for winter and to improve your home’s resistance to damp and cold. There have been a few nearly frosty mornings here in Canterbury and terracotta, concrete or stone pots on your deck should be protected from frost. Again I have written Yellow How To guides on these subjects, see here.

Have a wonderful Easter break whatever you are doing.

I think it is likely to mean more rats and mice than usual invading our homes looking for food and shelter this autumn and winter.

How to Stop Rats and Mice

1. If you have seen rats or mice, or evidence of them around your property, the most efficient and effective way to get rid of them is to use rodenticide baits sometimes in conjunction with simple traps and proofing.
2. NO Rats & Mice rodenticide bait is placed at strategic, safe points, inside and outside the buildings, in order to reduce populations around the building and to deal with individuals that enter, before an infestation can take hold. The NO Rats & Mice Weatherproof Blocks is a rat bait well suited to using outside or in damp areas while NO Rats & Mice with Tracking Powder is ideal for use in dry areas inside the house. If you do not wish to use toxic rodenticide bait, Kiwicare Natural NO Rats is a bait that is harmful only to rodents. However it should only be used in dry areas where other food sources can be controlled.
3. NO Rats and Mice Traps are useful to use where poison baits cannot be placed or as a helpful way of catching rodents that are ‘dopey’ from taking bait. The rodents can then be removed without risk of causing an unpleasant smell.
4. Prevent the rats or mice getting in. A mouse can squeeze beneath a door if there is a gap large enough to fit a pencil a young rat is only a little larger than a mouse! Draft excluding brush strips, are an ideal method of proofing such gaps. However, there are almost always other possible entry points around any building. So it is always wise to keep fresh rodenticide bait in place in safe places such as the roof void so that any rodents that get in are dealt with before you know about them.
5. This is an important and often overlooked aspect of controlling pests. For example, rodents are what we would call agoraphobic, they fear open spaces, and like to be under cover. A wide clear area around a building will deter rodents from reaching and entering the building. And the removal of available food and shelter from within a building can have a powerful deterrent effect.

Stay rodent free this winter.

What is the difference between rats and mice?
The difference is in their size or the size of their incisors.