The rodents make up the greatest number of species of mammals throughout the world. In Ireland, the Order Rodentia includes the Red and Grey Squirrel, the Wood and House Mouse, the Brown and Black Rat and the Bank Vole. The rodents lack canine teeth, but like the rabbits and hares, have specialised incisor teeth. Indeed, the teeth are the most characteristic feature of the Rodentia. The incisor teeth continue to grow throughout the life of the animal. For this reason, it is necessary to supply pet rodents, (mice, guinea pigs etc.) with a supply of wood etc. in their cage to enable them to gnaw continuously.
The Red Squirrel
The Red Squirrel is found throughout the country. It is smaller than the Grey Squirrel and found in a wide variety of habitats, ranging from coniferous forests to parklands. They feed mostly on seeds and berries. Although it is believed that the squirrel can use its fore-limbs for a variety of activities, recent research shows that the squirrel must first pick up a food item (e.g. nut) with its teeth and then transfer it to its paws while in a hunched position. This is clearly an ingrained action. Red Squirrels are known to hoard food items from times of plenty to be used at a later date. Red squirrels are more difficult to observe than Grey Squirrels. One reason for this is their tendency to spend a greater amount of time high up in coniferous trees. One of the few places left to see red squirrels in Dublin is the National Botanic Gardens in Glasnevin. The Red Squirrel is a protected species under the Wildlife Act, 1976.
The Grey Squirrel
The Grey Squirrel is an introduced species. Although confined mostly to the north and east of the country, the Grey Squirrel is becoming the squirrel most commonly seen in our woodlands and parks. Much has been written about the effect the Grey Squirrel is having on our native Red Squirrels. It is true that they are larger and aggressive and many people believe that the decrease in population of our Red Squirrels is due to the Grey Squirrel. However, the situation is much more complex. Red Squirrels prefer large coniferous woodlands while Grey Squirrels prefer mixed and broadleafed woods. Contrary to most beliefs, the Red Squirrel is not dependent on acorns. In fact, they find them somewhat toxic. As large tracts of coniferous woodlands disappear, this breaks up the habitat of Red Squirrels making it more difficult for them to hold territories. Grey Squirrels feed on acorns and are more omnivorous and in areas where both co-exist, appear to be more successful. Grey Squirrels have filled the vacuum left by the latest Red Squirrel decline.
Both Red and Grey Squirrels are active by day, sleeping by night in their nest or "drey". Both have two litters per year, with an average of three or four per litter. The young leave the nest about 7 or 8 weeks after they are born. Red and Grey Squirrels do not interbreed.
Squirrels, both Red and Grey, are responsible for removing the bark from the growing tips of branches on trees (particularly beech and sycamore) to enable them feed on the sugar rich sap beneath. This damage can be quite severe, making them the enemy of foresters and gamekeepers suspect the Grey Squirrel of taking the eggs of pheasants.
The Wood Mouse
The Wood Mouse (also known as the Field Mouse) is extremely common and widely distributed in Ireland. It has large eyes and a long tail. Apart from woodlands, it is also found in hedgerows and gardens. In fact, as it is a burrowing animal, it tends to be found whereever suitable soil is present. The Wood Mouse is a nocturnal animal, only occasionally to be seen in daylight hours. It feeds almost entirely on seeds. Insects and snails may be taken. Like other animals, the Wood Mouse will store food in late autumn. The breeding season is from March to October. Pregnancy lasts 20 days and they have two or three litters per year generally with an average of five young per litter. Mice born early in the breeding season are ready to breed before the end of the same season. The lifespan of a Wood Mouse is short, seldom reaching two years. The Wood Mouse forms an important part of the diet of owls and Kestrels as well as Foxes and Stoats. In cold winters, the Wood Mouse will regularly come into houses and out buildings. Its bright golden coat will help distinguish it from the more familiar House Mouse.
The House Mouse
The House Mouse is found throughout Ireland. They are nocturnal animals, although they do adapt to the activities of the human occupants. Although originally a seed eater, they have learned to exploit man and are now opportunistic omnivores, feeding on whatever is available (cereals, chocolate etc.) and have even been known to chew through electrical insulation. In general they will breed all year round, producing anything up to fourteen litters per year with anything up to twelve young per litter. Populations can therefore build up rapidly and they need to be controlled. They are Ireland's most successful mammal apart from the Pygmy Shrew. By far their greatest predator is man followed by the domestic cat. House Mice are social animals and communicate with each other by scents and vocalisations. Territorial aggression between males can become intense, especially in over-crowded conditions. The damage caused by House Mice is not as great as that done by rats. However, like rats, they are carriers of leptospirosis, a bacterial infection, that can be fatal to humans.
The Brown Rat
The Brown or Common Rat is a late arrival to Ireland, arriving here aboard ships less than 300 years ago. They have rapidly established themselves as a major pest. The key to this success is its versatility. The Brown Rat thrives wherever man grows or stores food. Their senses of smell and hearing are very sharp, but they have poor eyesight. Brown Rats are excellent diggers and excavate extensive burrow systems. These can be seen at the base of hedges and in fields, particularly those of germinating corn where they leave a series of tell-tale "scrapes" behind. They are omnivorous, feeding on whatever food is available, but preferring food rich in starch or protein. The Brown Rat builds a rather bulky nest of any available material and the litter can be as large as fifteen. They can have up to five litters per year. Control of the Brown Rat is necessary, especially as they can transmit a number of potentially fatal diseases (e.g. Salmonella and Leptospirosis). Up to 50% of rats in some populations may carry Leptospira, which is excreted in their urine. In the 1950's an anticoagulant called Warfarin was developed. This prevented the blood from clotting and caused the poisoned rats to die from haemorrhages. A drop in the numbers of their natural predators (Stoats and birds of prey) may also be responsible for increases, especially locally, in their numbers.
The Black Rat
The Black Rat is now rare in Ireland. It first arrived here in the Middle Ages aboard sailing ships. Lambay Island, off the coast if Dublin, is one of the few areas in the country where they still reside. The Black Rat is smaller than the Brown Rat It is mainly omnivorous, but prefers fruit, grain and seeds.
The Bank Vole
The Bank Vole is the only vole found in Ireland. It is an introduced species and found in the south and west of the country. It was discovered in Co. Kerry in 1964. Its habitat is that of dense undergrowth. It generally avoids areas where ground cover is scarce. They are good climbers and jumpers and they excavate burrows and construct underground nests. It is mainly nocturnal, but may occasionally forage for food, during the day. They are omnivorous, feeding mainly on berries, seeds and fruits although they are known to be cannibalistic! The breeding season is between April and September and Bank Voles can produce litters as quickly as every four weeks with an average litter size of four. The Bank Vole population is increasing in Ireland and it is possible that they may become an increasingly important element in the diet of foxes and owls. Bank Voles can cause damage in gardens and forestry plantations and may therefore need to be controlled.
Within the Order Insectivora, (the insect eaters) are two Irish mammals, the Hedgehog and the Pygmy Shrew.
The Hedgehog is possibly the most easily recognised mammal in Ireland. It possesses a coat of protective spines and its overall colour is greyish brown. The Hedgehog is known as the gardener's friend for the good work he does in the garden by eating slugs and snails. Hedgehogs can be noisy animals and will often attract your attention to them in the garden. They will emit a wild scream, like a squealing pig, when they are severely frightened. They are extremely agile animals and are good climbers of walls and fences. If they fall off, they curl into a ball, as they fall, to land unhurt, cushioned by the thick layer of spines. Hedgehogs can also swim. However, many have been found drowned in shallow plastic lined garden ponds due to the steep smooth sides from which they can't escape. Hedgehogs are also thought to collect apples in autumn by deliberately rolling on them so that the apples become impaled on their spines. These can then be carried off to be eaten or stored. Hedgehogs are also known to produce a mass of saliva, which they spread over their spines, a process called "anointing". The purpose of this is still not understood. It has been reported that hedgehogs suck milk from cows. It is true that hedgehogs like milk and they do frequent cow fields but they are far too small to reach the teats of cows, unless they are lying down. However, the teats are very large and the hedgehog has a small mouth (and also sharp teeth!). What is most likely, is when the cow lies down, milk tends to flow from an overfull udder and could be lapped up by a foraging hedgehog. Hedgehogs do build their nests in garden rubbish and gardeners should be careful when burning such rubbish.
The Pygmy Shrew
The Pygmy Shrew is our smallest land mammal. It is found throughout Ireland though seldom seen, as they stay well hidden in the undergrowth. They have very poor eyesight and they hunt by smell and by touch, using well developed whiskers. While hunting, it frequently squeaks and it must eat at least its own body weight in food per day. Because of its high metabolic activity, the Pygmy Shrew can only sleep for a few hours at a time, otherwise it will starve. Pygmy Shrews breed from April to October with two or three broods per year producing about six young each time. In autumn the Pygmy Shrew grows a thick coat to help survive the winter. However, due to a shortage of food and the cold, many do not make it. The average life-span is about 18 months. Because of their aggressive nature, sharp-tongued women are sometimes called shrews or are said to have a shrewish nature. They are preyed upon by owls, foxes and stoats. Many are brought in by domestic cats, and in fact this is often the only time that many humans ever get to see a live Pygmy Shrew.
The herbivorous mammals in Ireland are the Rabbit and the Hare.
The Rabbit was introduced into Ireland by the Normans in the 13th Century and is found throughout the country. It is thought that they were introduced from the continent to provide sport for noblemen and as a new source of food and fur. They are normally active from dusk onwards, but if the area is quiet they will appear in broad daylight to feed. Because Rabbits are herbivorous, and because plant material is so hard to digest, they pass their food through their digestive system twice. After the faeces are passed pout of the body, they will ingest it to digest it once again to enable a further extraction of nutrients. Rabbits have large ears and their hearing is very sensitive. Their eyes are set on either side of the head, thereby enabling them a greater field of view. They feed mostly on grass and live in underground burrows called warrens. Although they are capable of breeding throughout the year, most are born from April to June. The viral disease, myxomatosis, was introduced in Australia to reduce their huge numbers there. It was introduced in Ireland in the 1950's and is spread by the rabbit flea. There was widespread condemnation in Ireland of the use of this method of control.
There are two species of hare in Ireland, the Brown Hare, which was introduced from mainland Europe and the native or Irish Hare. The Brown Hare is only found in the lowland areas of the northeast of the country, whereas the Irish Hare is present all over the country. The hare lives out in the open from the moment of birth. Young hares are called leverets and they have a coat of fur and are soon fully mobile. Hares rest up in a form which is usually orientated so that the animal can sit with its back against the wind. Hares are commonly observed in early spring, often careering around the countryside, "boxing", apparently oblivious to danger. The hare's large eyes have a very glassy appearance which enhances the idea that there is madness in the stare. Recently, hares have taken up residence along the grassy verges of airport runways and often run alongside planes at take off and landing. Hares were very common on the Bull Island in north Co. Dublin, but in recent times their numbers here have been reduced due perhaps to the number of dogs present. The male is called the Jack and the female, the Jill. Although a protected species, hares may be captured, under licence, for coursing by muzzled greyhounds in accordance of the rules of the Irish Coursing Club. Hares used for coursing must be tagged prior to release and not used for coursing again.
The remaining land mammals are from the Order Carnivora, and they include: the Fox, Stoat, Badger, Mink, Pine Martin and Otter.
The Fox is common throughout Ireland and unlikely to be mixed up with any other animal. They are found in all types of habitat and recently are appearing with more regularity in suburban gardens. They have been known to breed in the city of Dublin for over 50 years now. Although classified as a carnivore, foxes also take fruit and berries and are known to raid dustbins in cities. Many people feed foxes with "titbits" nightly to encourage them into the garden. Male foxes are called dogs and females, vixens. Young foxes (cubs) are born in an "earth" below ground. The vixen bears one litter of four or five in a season. The young are born blind with short, dark fur. It is a major task for the adult foxes to provide enough food for the growing cubs. Foxes have long been persecuted by man, particularly farmers and gamekeepers. Foxes may indulge in surplus killing, e.g. young reared game birds or hens in a hen house. Local gamekeepers kill large numbers of foxes. However, the effect this is having on numbers of game birds is generally unknown as other foxes soon move into the vacated territory. The effect of fox hunting on the population of foxes is also unclear. It is unlikely that this seriously affects the population countrywide, however, it should not be forgotten that individual foxes can die very painful deaths all in the cause of this "sport".
The Stoat is a small but savage animal and the only mammal in Ireland that regularly kills prey much heavier than itself. They are very curious animals and are often seen out in daytime, however, they commonly hunt at night. The Rabbit forms the major part of its diet. The Stoat kills the Rabbit by repeated bites to the back of the neck, inflicted while it clings on to its victim's back. Rats, mice, birds and their eggs are commonly taken. Like the Fox, Stoats also indulge in surplus killing Stoats breed only once a year and the young are born from March to May. Anywhere from six to thirteen young may be present in the litter. Stoats are unpopular with gamekeepers and farmers, due to their liking for game birds and poultry. However, they do keep down agricultural pests such as Rabbits and rats. Apart from man, the Stoat has no natural enemy.
The Badger, old Broc, has often been described as our oldest landowner. There is no mistaking the Badger with its white face and distinctive black stripes running over each eye. They are nocturnal and widespread in Ireland. The Badger home is underground and is called a sett. This is a series of intercommunicating tunnels and chambers, generally found in woodland or edge of woodland often on a slope. Setts can have a large number of entrances and hundreds of metres of tunnels. They are excavated by the Badgers and up to 25 tonnes of soil have been known to be removed by them. Badgers are communal animals with one male dominant in each group. Badger setts can be occupied by a clan for many generations. They are regularly cleaned and extended. In most setts, Badgers use only one chamber for breeding. Badgers spend a lot of time at play and grooming, suggesting that they are sufficiently successful and do not need to spend every waking hour searching for food. Play is very important in social animals, strengthening the bond between members of the group. Although classed in the Order Carnivora, the Badger is truly omnivorous. The favourite food is earthworms, although acorns, beech mast and berries is taken along with beetles, slugs, snails and small mammals. Bovine tuberculosis is endemic in Badgers, with most groups containing at least one infected animal. A lot of debate is ongoing as to whether outbreaks of TB in cattle is due to cross-infection from Badgers. Another major threat to Badgers is the illegal "sport" of badger-baiting.
The Mink is a member of the weasel family and the mink found in Ireland is the American Mink which is bigger than the European Mink. This mink is an escapee from mink farms which were established here in the 1950's. The Mink has long been valued for its pelt. It was inevetible then, that some would escape and breed in the wild. They occupy a diversity of habitats, woodlands and parklands, particularly those with access to streams and ponds. Unlike Otters, they are active during daylight hours. They are not as efficient at hunting in water as the Otter, but this is more than made up for when on land. The diet implies that the Mink is an opportunistic predator feeding on duck, pheasant, fish, crab, rodents, eels etc. As with Foxes and Stoats, surplus killing occurs which can lead to problems on islands with bird colonies. Mink have linear territories and the removal of a dominant male can lead to great unrest among the sub-ordinates to take that place. As the Mink is very destructive of poultry and game stocks, control by trapping is necessary. However, the overall impact of Mink in Ireland has not been as catastrophic as was first predicted.
The Pine Marten
The Pine Marten is a somewhat cat-like animal spending most of its time on trees (hence the Irish name, cat crainn). It has a body similar to the Stoat, but larger and with a bushier tail. Pine Martens are found mainly in the west of the country and their numbers are increasing lately as has their spread. Their preferred habitat is deciduous woodland with good ground cover. They are solitary animals. Although a very skilled hunter, Pine Martens hunt primarily on the ground, feeding mainly on rats and mice and occasionally taking squirrels. They breed once a year and the litter of generally three animals are born in April. The young are called kits.
The Otter, although rare throughout Europe is found in every Irish county. Otters live in lakes, rivers, streams and around our coasts. Coastal otters require a source of fresh water to wash salt from their fur to maintain its insulating properties. The diet of the Otter is primarily fish, both coarse, but also includes Salmon and Trout. Birds and young mammals may also be taken. Otters rest up in a "holt" and an otter may have a number of holts within its territory. Female otters often make their holts under the roots of an overhanging alder tree. The cubs are protected from enemies because the entrance is under water. Adult Otters breed once a year and the young are born generally in the summer months. Cubs stay in the holt for about 8 weeks after birth and they are generally reluctant to take to the water, needing encouragement from the mother. As the Irish population is now the healthiest in Europe, this population is of international importance and strictly protected.
The remaining land mammals in Ireland are the deer and the feral goat. These are members of the Order Artiodactyla (the even-footed mammals).
The Red Deer is the largest deer in Ireland. They are most common in counties Kerry, Donegal and Wicklow (those in Donegal and Wicklow were introduced in the 19th Century from Scotland. They are herbivores, feeding on grass, leaves, acorns and herbs. They can damage woodlands by stripping the bark from young trees in order to obtain minerals contained in the inner bark. Sika Deer were introduced to Ireland in the mid 19th Century and are the smallest of our deer. They are found in counties Wicklow, Wexford, Kerry, Tyrone, Fermanagh and Limerick. However, their genetic diversity is poor as they have all descended from a small founder population. Sika are opportunistic feeders, taking whatever vegetation is available.
Fallow Deer were first introduced to Ireland after the Norman invasion. They are now widespread and the most common deer in Ireland. The best known herd of Fallow Deer in Ireland is in the Phoenix Park. They are here for over 300 years now and this herd numbers about 650 animals. The best time of year to view these beautiful animals is in October or November, i.e., the rutting season. The rutting season lasts about four weeks and during this time dominant bucks form territories and mate with the does. They are extremely noisy at this time, often for hours on end. They feed off grass, leaves and twigs, cropping branches to about 2 metres. Their coat colour varies considerably. However, the summer coat is a rich glossy brown with white spots. The tail is white below and black on top.
The Feral Goat
Feral or wild goats are found in small herds on remote mountain slopes and off shore islands. They feed mainly on grass and shrubs. The young (kids) are born in February or March and are unable to run with their mothers for several days after their birth and are often found lying motionless under cover. These kids are not abandoned and should be left alone. Occasionally twins are born. One of the more famous goat herds in Ireland is that which inhabits the Golf Links at Lahinch, Co. Clare. They are said to forecast the weather more accurately than a barometer, for, when rain is imminent, they congregate close to the Clubhouse. In fine conditions, they are well spread out over the golf-course.