Rats and Mice
Rats and Mice
Rodents (from Latin rodere, “to gnaw”) are mammals of the order Rodentia, which are characterised by a single pair of continuously growing incisors in each of the upper and lower jaws. They are the most diversified mammalian order and live in a variety of terrestrial habitats, including human-made environments.
Most rodents are small animals with robust bodies, short limbs, and long tails. They use their sharp incisors to gnaw food, excavate burrows, and defend themselves. Most eat seeds or other plant material, but some have more varied diets. They tend to be social animals and many species live in societies with complex ways of communicating with each other. Mating among rodents can vary from monogamy, to polygamy, to promiscuity. Many have litters of between 6-12 and can do so many times a year.
Rodents have been used as food, for clothing, as pets, and as laboratory animals in research. Some species, in particular the brown rat, the black rat, and the house mouse, are serious pests, eating and spoiling food stored by humans, and spreading diseases. Accidentally introduced species of rodents are often considered to be invasive, and have caused the extinction of numerous species, such as island birds, previously isolated from land-based predators.
Mice- General appearance
The House Mouse and sometimes the long tailed field mouse can be found in buildings as they seek warmth and shelter for nesting sites and food.
House Mice generally are of 60-90mm long, and the tail can add an additional 100mm to the overall length. They weigh less than 25g and can range in fur colour from light brown to grey.
Rats- General appearance
The two types of rat found in the UK are- Rattus Norvegicus which is commonly known as the Brown Rat or Common Rat. The Rattus Rattus, known as the Black Rat or Ship Rat is now rarely found in the UK.
The Brown Rat is the larger of the rats in Britain, often weighing over half a kilo and measuring about 23cm, without counting the tail. It has a blunt muzzle, small hair-covered ears and a tail that is shorter than its body. The Black Rat weighs half as much and is shorter. It has a pointed muzzle, large, almost hairless ears, a more slender body and a long thin tail that is longer than its body.
Both Mice and Rats carry much of the same diseases, Mice are generally more tolerated. However they are more curious and bolder and can come into contact with more items such as cutlery food products and work surfaces. These include Salmonella and Listeria, which can cause food poisoning.
Rats carry many diseases which they can spread to humans, normally through their urine. including; Leptospirosis or Weil’s disease, Salmonella, Listeria, Toxoplasma gondii and Hantavirus.
Mice are erratic, sporadic feeders, nibbling at many sources of food rather than taking repeated meals from any one item. They do not need free water to drink as they normally obtain sufficient moisture from their food.
Rats feed mostly at night and an average rat will eat 50g of food a day. Preferred foods for both Mice and Rats are cereal products, however they are omnivorous and will eat almost anything that humans eat.
Both will eat from our dwellings and any food stores for domestic animals are viable as well.
House mice usually run, walk, or stand on all fours, but when eating, fighting, or orienting themselves, they rear up on their hind legs with additional support from the tail – a behaviour known as “tripoding”. Mice are good jumpers, climbers, and swimmers, and are generally able to maintain contact with vertical surfaces.
Mice are mostly nocturnal; they are averse to bright lights. They live in a wide variety of hidden places near food sources, and construct nests from various soft materials. Mice are territorial, and one dominant male usually lives together with several females and young. Dominant males respect each other’s territories and normally enter another’s territory only if it is vacant. If two or more males are housed together in a cage, they often become aggressive unless they have been raised together from birth.
Mice are generally afraid of rats which often kill and eat them, a behaviour known as muricide.
The Brown Rat is nocturnal and is a good swimmer, both on the surface and underwater, and has been observed climbing slim round metal poles several feet in order to reach garden bird feeders. Brown rats dig well, and often excavate extensive burrow systems.
When rat populations are large, a hierarchy develops within a burrow. Stronger individuals become dominant, while weaker ones are subordinate. Males no longer protect female burrows. When a female is oestrus, several males mate with her sequentially, in the order of their social dominance.
Rats exhibit aggressive behaviour when threatened. They may fight, chase, bite and box. Rats also display some behaviours such as sidling and belly-up defensive postures.
For the treatment of Mice there is not much in the way of preparation prior to a mouse treatment except for keeping food stuffs out of reach of mice if they are in these areas and keeping hygiene to a high standard. It is very important that people are aware of the disease hazard that they can cause. If you suspect they have been on work surfaces or in drawers containing cutlery or foodstuffs then these must be washed before use and foodstuffs destroyed.
Effective mouse control involves sanitation, mouse proof construction and population reduction. The first two are useful as preventive measures. When a mouse infestation already exists, some form of population reduction is almost always necessary. Reduction techniques include trapping and poisoning. Trapping will only reduce a mouse population, rarely eliminate it completely and as they breed so quickly elimination is the desired result. Poison baiting is the quickest way to deal with a mouse infestation. The right type of bait in the right places has to be used for the whole population to feed on the bait for the treatment to succeed. The bait has to be put in the correct places, mice are territorial and if the bait is not in a mouse’s territory then it won’t take the bait.
Mice are fussy feeders and surprisingly more resistant to poisons than rats or other rodents. Mice do not need much food and can extract all the moisture from the food they eat. Mice eat only 1/20th. to 1/10th. of an oz. per day. The baits and poisons used by PEST UK are widely recognised as the best available for the treatment and complete eradication of a mouse infestation. The technician will make at least 2 visits.
With regards to Rats- keeping a record of where you see rats, asking your neighbours if they have them, leaving any droppings or damage for the technician to look at. If you are feeding birds then stop. If you have a compost heap then stop putting food on it. Identifying & dealing with the food source is the most important factor in dealing with a rat infestation.
Rat infestations are normally dealt with a cereal based poison bait containing an anticoagulant poison called Sakarat*, which contains the poison Bromadioline 0.005%. This poison usually requires that the rats feed several times before dying or if they consume enough poison to give them a lethal dose on their first feed they will not suffer any ill effects until some time after feeding. This ensures that they do not become suspicious and associate the bait with illness or death and a ‘complete kill’ takes place killing all the rats in the colony.
It can take up to 7 days before the rats start feeding on the bait as they are suspicious of new objects. It is important to achieve a complete kill as they breed at such a rapid rate that any survivors soon replace the dead with their offspring. (A healthy female rat will live for two years and can produce up to 60 young per year).
In heavy infestations rats can be seen feeding during the day, these are usually the subordinate old and weaker animals that feed during the more dangerous hours of daylight to avoid the more aggressive dominant rats. If you see rats during the day time it usually means the problem is quite severe.
Rats are attracted to the smell of other animals and their food, so particular care should be taken when feeding pets, wild birds etc., the storage of any foodstuffs and the disposing of rubbish, including animal droppings. Should you find any dead bodies they must not be handled without protection and should be buried or burnt.