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 30% in urban areas and between 50% and 75% in rural 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. As of late 2024, the IUCN updated the status of the Western European hedgehog to "Near Threatened" due to sharp declines across Europe.
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. Until recently in Ireland, hedgehogs were not monitored and very little research has been done on the species here. However, current projects underway with University of Galway, NPWS and the National Biodiversity Data Centre. It is hoped that the current study will provide baseline data in order to monitor their numbers in the future.