Hedgehogs, 9 March 2011

The presenter of this talk, Dr Nigel Reeve, is currently Head of Ecology for The Royal Parks in London, but has a long-held interest in hedgehogs (Erinaceuseuropaeus) since studying them for his PhD at the Royal Holloway, University of London and during his tenure as a lecturer at the University of Roehampton.  Research into their ecology is certainly needed since, although the hedgehog is regarded with affection in this and many other countries, recent data such as those from the Tracking Mammals Partnership suggest that the UK population, sadly, is in decline.  As a result it was added to the BAP priority list in 2007.

European hedgehogs are native throughout northern and western Europe, and have been introduced to New Zealand where they are considered a pest species.  They are variable in colour – blond animals are found on Alderney apparently! – but all of course feature a coat of spines, which are some 2.5 cm long, bulbous at the body end and very sharp at the other.  As a result they are not successfully predated by many animals, although badgers can and do eat them, as well as competing with them for food – this is principally beetles, caterpillars and earthworms but hedgehogs take a wide range of invertebrates including slugs, snails and fly larvae.  They will also exploit other food sources offered, such as cat food put out by helpful householders – but bread and milk is not recommended.

Another threat to hedgehogs is accidental disturbance or even destruction while in the nest, especially during hibernation which takes place approximately November to February, in a nest of leaves (oak and beech being ideal) constructed in a confined space under vegetation or man-made structures such as sheds.  Rescue centre records show that 47% of hedgehog admissions and 38% of deaths are human-related, with hazards including pits and steep-sided ponds, trapping in sheds, garden netting and litter, strimmers, traffic, garden tools, bonfires and pesticides.

Hedgehog courtship and mating – which can take several hours – takes place in the spring, and the young are born mainly between July and September after a gestation period of 33 days.  Recent studies show evidence of polyandry, i.e.  multiple paternity within the same litter.  At birth, the young hedgehogs' skin is inflated with fluid to protect the female against their spines, which at this stage are white, with new, brown adult spines starting to come through after 7 days.  The young begin to forage on their own after 4 weeks and are weaned at around 40 days old.

Nigel's research in the late 70s and early 80s, which was carried out at the Ashford Manor Golf Club in Surrey, entailed tracking individual hedgehogs in order to monitor their behaviour, using a variety of techniques including radio-tracking.  He found that individuals' home ranges, once established, remained fairly constant, which could pose problems for animals if habitats they use habitually are removed or changed.  Males range three times as widely as females, covering about 40 hectares, especially in the breeding season.  Edge habitats such as hedgerows are preferred, followed by grassland, with other habitat types less favoured: maintaining borders of invertebrate-rich long grass and scrub along hedgerows, and ensuring connectivity between suitable habitat areas, are therefore important for hedgehog conservation.  While suburban areas with gardens can be good for hedgehogs therefore – provided there are not too many badgers or busy roads – maintaining connections between gardens is essential.  Some aspects of hedgehogs' behaviour are not well understood,such as the use of each others' summer nests, and the habit of self-anointing the spines with frothy saliva, the purpose of which is unclear.

Further information on these endearing – if not exactly cuddly! – mammals, including measures householders can take to help conserve them, can be found on the British Hedgehog Preservation Society website: www.britishhedgehogs.org.uk.

Lynn Whitfield