Rat or Mouse - a guide to identification
Posted on 10th February 2020 at 16:21
When it comes to delivering a pest control service, rodents and particularly rats and mice are our biggest pest issue in Henley; these animals are active all year long infesting homes, gardens and businesses right across the area. Many of the mouse species that we get called out to are in fact field mice and these are an important part of the environment: there is no problem with mice in the garden but they’re not for the indoors.
We used so see a trend with internal infestations from mice and rats where they would enter our buildings for the warmth in the late autumn, leaving in spring and going back outdoors. We used to have a ‘rat season’ in Henley but this trend seems to have ended, we are seeing rats inside people's homes all year long.
We think that the reason for this is that the resident population is so high, once they have discovered a territory they will not leave it for fear that another family of rats move in – we had constant rat activity in houses across the region last summer.
Many of our customers will telephone us and tell us of their experience of what they call a mouse; most people cannot tell the difference between a rat and a mouse and so we have put together a visual guide to explain the differences between the species.
The first species that we will look at are mice and when it comes down to these we talk about two groups of mice – field mice and house mice. To add to the confusion there is no such thing as a field mouse but we looking at the whole group of small rodents that populate our gardens and are considered to be a pest when inside the property. Mice, voles and shrews are all what I call accidental pests; if they hadn’t gotten inside we wouldn’t be concerned about them.
These small rodents can squeeze through gaps smaller than your little finger so its very common to have one of this group inside a property; gaps around door thresholds, open plastic air bricks and older corroded metal ones will all allow mice in. They are also fantastic climbers and they will climb up walls and plants to get in via old redundant pipe holes and through the roof.
Field mice have a relatively short lifespan of a single year and in that time the female mouse will produce between 2 and 4 litters of baby mice; a maximum of around 24 baby mice from a single mother each year so you can see how the numbers of these rodents increase.
Field mice are around 10.5 cm in length with a tail that is between 6 and 9 cm, their colouring runs from beige to a reddish brown coat with a white underside, smaller eyes and ears than the house mouse.
The house mouse is a completely different animal in relation to its country cousin and we consider these animals as pests in the same way that we do for rats; the house mouse can be difficult to eradicate from old buildings that have been converted to flats and newer purpose-built developments.
As around 80% of house mice carry salmonella these present a significant health hazard to residents of buildings who have a house mouse infestation.
Both types of mice are largely nocturnal and due to their tiny size they can often squeeze through gaps and get onto the back of plasterboard ceilings; this acts like a drumskin making the mice sound like they’re huge; field mice are smaller than their urban cousin and have much larger eyes – this is thought to be because of the lack of artificial light in their proper environment.
House mice thrive in the urban environment, eating whatever they can get and if they have access to a food source that contains enough moisture they will not have to find a water supply; some of the dry dog biscuits will contain enough moisture for the mice to get by on.
The need for water is one major difference between mice and rats, as rats will always need to drink. House mice will breed all year long as they have access to warmth and a supply of food, a female house mouse may have eight litters in a year and produce over 100 baby mice during that time. In addition to that house mice mature earlier than field mice and these youngsters will produce their own offspring in three months’ time, bringing about large rapidly growing infestations.
The house mouse is smaller than the field mouse around 7 to 9.5 cm with a tail of the same proportion to the body, they are often confused with young rats and the positive way to make identification is that they have small feet, large ears and eyes.
Shrews and voles fall into the category that is covered by “field mice”; the rodenticide that we use as professionals is licensed for particular species and all field mice are excluded from any active ingredient found in rodenticide. The reason for this is that they form the base of a food chain that feeds owls and other raptors and as a residue of the poison remains inside the rodent so these birds of prey are systematically being poisoned through the use of rat and mouse poison. Our approach when it comes to dealing with field mice and all other species of rodent is to start with traps and proofing the entrance points; rodenticide is only used as a last resort.
We are proud to ne members of the Campaign for Responsible Rodenticide Use and our aim is to reduce our use of rodenticide in order to protect the environment.
Rats are a common pest in urban situations and these rodents will breed all year round; with access to stored food stuffs and warm properties to live in, as long as this situation remains so rats will continue to breed and a young rat can easily be mistaken for a mouse.
Typically, the female rat will have around six litters each year and each litter will have between 9 and 12 twelve baby rats. These will quickly grow and they will become sexually mature and able to produce their own young after 5 or 6 weeks. If you run the maths on this scenario it means that a single rat can produce a family dynasty 2000 strong in a single year. There is a figure of 12 million rats now living in the UK which is probably over inflated. Rats are prone to disease, accidental death and the work of pest controllers but given the odds the rat population in the UK is rising.
Rats are generally grey in colour and occasionally a lighter more ginger colouring runs through the population whilst pet rats with white colouring are genetic mutations and deemed as ‘fancy rats’ – sometimes we’ll see piebald rats and this will be as a result of an escaped rat breeding with the wild population.
We have two species of rats living in the UK – the Norway rat and the Black rat; the rat that we see in Henley is the Norway rat and this will be called other names like sewer rat, farm rat or town rat. Its highly unlikely that you’ll see a black rat as these are found in and around dockyards where they are known as ship rats.
Rats have a stocky body with wide powerful back legs, these rodents are good climbers using their tail for balance and great jumpers, the Norway rat can leap almost a metre upwards from a standing start; that’s almost from the floor to the kitchen worktop if you ever wondered how they get up there.
Rats have smaller ears than the house mouse and a thick hairless, scaly tail and this is by far the easiest way to identify the two species: thick scaly tail which is shorter than the body length and that’s a rat, a tail with fine hairs on it about the same length as the body if not longer and that’s a mouse.
If your rodent infestation has gone on for any length of time then you will have faecal deposits or droppings around the property and these will give you another idea of whether it’s a rat or a mouse if you haven’t actually seen the culprit! Mouse droppings are much smaller than a dry grain of rice and similar in shape, in that they have sharp pointed ends. These will be black in colour and found in high numbers scattered about but with more closely deposited where the animals run. Look around edges and especially corners beneath kitchen cupboards and underneath loft insulation; sometimes you’ll see round burrows dug through loft insulation as mice will be under this material and tunnel up through it.
Due to their size rats will run on top of loft insulation so look for creases where the material is compressed, all rodents will leave a pheromone trail which denotes a ‘safe’ route and they will habitually follow this leaving a trail.
Rat droppings are much bigger than a grain of rice, around about 10 mm in length and these have rounded ends and sometimes curved like a banana, these will be found scattered about in a similar way to mice. With rats there is a constant urine stream, and this is usually the most noticeable sign of their presence especially in a confined area like under the floorboards or even the loft.
When it comes to dealing with all types of rodents including squirrels, we recommend that you use a pest control company who will do more than just lay poison inside your property, eradicating the animals is only half of the story as you need to identify the route in and have a plan to resolve the problem for the long term.
There is the question of how the animals are getting inside and for that the answer you need to thoroughly investigate the situation, a straight to poison approach will give you a swift result but it will probably fail to identify the access point; this means that without any proofing the animals will be back in time.
Our approach to all rodent problems: rats and mice along with squirrels is through investigation, trapping to confirm the correct theory and then proofing to seal up the access point; its more difficult than simply putting down rodenticide and it takes longer but the overall goal is to keep the animals out for good.
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