The Hedgehog (Erinaceous europaeus) is one of our most recognisable animals. Their Irish name ‘An Gráinneog’ means ‘little ugly one’. They are generally regarded with great fondness due to their cute appearance, quirky habits and their taste for eating garden pests. While hedgehogs are perceived to be common and widespread, there has been very little research on the species in Ireland to date. Thus, we have no data on the size or status of the Irish hedgehog population.
Many people are surprised to hear that hedgehogs are not actually native to Ireland. It is believed that they were introduced in the 12th century from Britain or the Continent, with some suggestions that they were brought here by the Normans for food. Despite its non-native status, the hedgehog is not classed as an invasive species but is considered naturalised in the Irish environment.
Hedgehogs are found all over the country except in wetlands, karst and mountain regions. They favour habitats that have plenty of diversity with mixtures of long and short grass, hedgerows, bushes and trees that provide food, shelter and wildlife corridors. Hedgehogs are solitary, nocturnal animals, emerging after dark to forage for food. They are not territorial but will forage within a large home range of approximately 10ha for females and 32ha for males. During the active season from spring to autumn, each one will keep several temporary nests where they rest during the day. When the temperatures drop from about November to March, they hibernate in nests carefully constructed of dead leaves under brambles, log piles or garden sheds. In mild winters, hedgehogs will wake up and look for food and may even move nests.
The hedgehog diet is composed largely of insects, particularly beetles and caterpillars as well as other invertebrates such as millipedes, worms and slugs. They will opportunistically take eggs, frogs, lizards and carrion. They are also keen on pet food that they may find in gardens. Over the season, they build up stores of white fat to sustain them during hibernation. They need to weigh at least 600g by autumn time to survive their winter sleep.
The breeding season takes place from March or April when the hedgehogs emerge from hibernation. Hedgehogs do not pair bond and after mating the male plays no role in rearing the young. Most pregnancies occur between May and July with gestation generally lasting between 31 to 35 days. The female constructs a large nursery nest where the litter of 4 to 6 hoglets are born. They are weaned by about six weeks. Hedgehogs may have a second or late litter in August or September, but these young are unlikely to grow large enough in time to survive the winter.
In Britain and Europe where hedgehogs have been more extensively studied, the research indicates that hedgehog numbers are in decline. Results from long term monitoring studies in Britain show that numbers there have fallen by nearly 50% in rural areas and by 30% in urban areas over the last two decades. These trends are due to loss of hedgerows and marginal habitats to intensive agriculture, increased road traffic, and predation or competition from the badger Meles meles.
Ireland has suffered many of the same ecological problems as Britain, and many native animals have suffered population declines due to habitat loss and degradation including several birds, invertebrates and mammals. It is possible that the hedgehog has followed a similar trend here, however, this cannot be confirmed in the absence of reliable scientific studies. The hedgehog is protected under the Wildlife Acts 1976 and 2000, however it is considered a common, non-native species, and so is not considered a priority for conservation in Ireland. It is hoped that the current study will provide baseline data in order to monitor their numbers in the future.