Hedgehogs have been voted the UK’s favourite mammal on several occasions during the past years! Brits seem to love hedgehogs for a whole range of reasons, including their cute and peculiar appearance, their role as slug controllers and their regular visits to our gardens, with a natural behaviour allowing us to come really close to them, unlike the majority of other wildlife species. In spite of this love for hedgehogs, the species is in serious decline, with an estimated one in three lost since the millennium.
With a WildCRU tradition in hedgehog research going back to 1996, starting with innovative work on their – far from positive – reactions to badger odour, and most recently Carly Pettet’s farmland work and a sortie with the desert-dwelling Ethiopian hogs that, despite their name, live in Qatar, WildCRU has now engaged hedgehog specialist Dr Sophie Lund Rasmussen, otherwise known as Dr Hedgehog, to continue the important research on hedgehogs.
The European hedgehog (Erinaceus europaeus) is widely distributed across western Europe and New Zealand due to its ability to adapt to a range of different habitat types. In spite of this, previous research on both national and local scales has either documented, or expressed concern about the likelihood of, a decline in hedgehog populations in several western European countries. As a consequence of the increasing documentation of a national decline, the International Union for the Conservation of Nature’s (IUCN) Red List for British Mammals classified the European hedgehog as “vulnerable to extinction” in 2020. It is therefore a priority to identify and investigate the factors responsible for this decline in order to provide the evidence necessary to underpin remedial conservation interventions.
These declines are believed to be driven by factors such as habitat loss and fragmentation, intensified agricultural practices, road traffic accidents, molluscicide and rodenticide poisoning, and in some areas badger predation.
Human effects on hedgehog decline
Previous research has shown that hedgehogs seem to prefer life in residential areas. This preference could be due to higher food densities affiliated with human occupation, including natural prey and anthropogenic food resources, sheltered climatic conditions and more suitable nest sites and a decreased risk of predation by badgers. In the UK, it is furthermore suggested that the hedgehog decline is currently more severe in the rural than urban areas. Since urban habitats may be more suitable for hedgehogs at the present time, it is relevant to describe the challenges hedgehogs face when living in this habitat type, to plan the optimal conservation initiatives directed at preserving hedgehogs in urban areas.
Green spaces in urban areas, such as parks, road verges, and gardens are often highly maintained and could support several populations of wildlife, for example, amphibians and smaller mammals. However, the fragmentation of the suitable habitats caused by roads, water‐bodies, and impenetrable fences is a challenge for the survival and genetic diversity of the populations. Initiatives taken by garden owners to make their gardens wildlife friendly by adding features such as nest boxes and feeders, may attract hedgehogs to gardens.
However, sharing habitats with humans also comes with a cost:
- Garden habitat quality in residential areas is weakened by the use of garden pesticides (insecticides, molluscicides, and rodenticides), which reduces the availability of natural food items for the hedgehogs and may cause secondary poisoning.
- Hedgehogs get seriously injured by garden tools and garden machines.
- They may get attacked by dogs in gardens.
- If piles of rubbish, garden waste, or logs for a proper bonfire, which all constitute excellent nest sites for hedgehogs, are not properly checked or moved to a new site before being lit, hedgehogs that may have chosen to take residence there, can get serious burn injuries or even die.
- Hedgehogs may be entangled in netting (football goal netting or protective plant netting) or litter, potentially causing extensive injuries or even death.
- Hedgehogs can fall into drains or deep holes in the gardens.
- Hedgehogs are excellent swimmers, but if there is no easy exit out of a pond or swimming pool, they will end up drowning.
- Fences and walls are getting increasingly secure, providing barriers for the hedgehogs to move freely in the residential areas in their search for food and mates. Therefore, an important initiative to help the urban-living hedgehogs is to make a “Hedgehog Highway” in or under your fence (13 cm x 13 cm) to ensure hedgehogs can access your garden.
The information gathered during a study on the ecology of hedgehogs in urban areas, can be applied to focus and optimise conservation efforts.
Currently, the research on hedgehog ecology and general health conducted at WildCRU include studies on the effects of robotic lawn mowers on hedgehogs, and a range of research projects based on samples from 697 dead hedgehogs collected through citizen science by over 400 volunteers in “The Danish Hedgehog Project” lead by Dr Sophie Lund Rasmussen. We will use these samples to investigate infectious diseases, cancer, the general composition of the microbiomes of hedgehogs (the collection of micro-organisms including bacteria, archaea, and fungi living in and on the bodies of the hedgehogs), their food choice, and lastly, which poisons accumulate in the hedgehogs. Previously, these samples have allowed Dr Sophie Lund Rasmussen to study the general health of hedgehogs, with research into their genetics and inbreeding, parasitology, age distribution, MRSA prevalence and dental health.
We aim to provide an important and detailed insight into the general health and survival challenges of the hedgehogs, enabling us to improve the conservation of this fascinating species so that future generations will also be able to enjoy the unique nature experience of encountering a hedgehog in their garden.
Facebook: The Danish Hedgehog Project
Hedgehog. Credit: Pia Burmøller Hansen
Hedgehog and Dr Sophie Lund Rasmussen. Credit: Pia Burmøller Hansen
Dr Sophie Lund Rasmussen counting growth lines (year rings) in sections of hedgehog jaw bones to determine the age of the individuals. Credit: Louise Marie Jønsson.
Checking dental health. Credit: Sophie Lund Rasmussen
Dr Sophie Lund Rasmussen in the lab cleaning bones from dead hedgehogs to study their morphology. Credit: Terese Egebjerg.
Dr Sophie Lund Rasmussen with a hedgehog and a robotic lawn mower. Photo credits: Troels Pank Arbøll
Dr Sophie Lund Rasmussen taking pictures of a hedgehog jaw bone section through a microscope for the purpose of age determination. Credit: Rien van Wijk.