||This page has been prepared for the "UK
Wildlife: First Aid and Care" and "Hedgehogs: Health &
Management" Wildpro volumes, and is designed for the
needs of the following species: Erinaceus europaeus - West European Hedgehog
- Some carers suggest that no pre-release preparation is required if these animals have been in care for a short
period of time.
- A period of acclimatisation in an outdoor enclosure is recommended for hedgehogs which
have been in care for more than a short period Some carers suggest that
all hedgehogs should be given a period of acclimatisation prior to
release. See: Long Term Care of Hedgehogs
- Must be able to recognise, catch, manipulate, consume and digest their natural diet.
- Must be capable of normal locomotion (movement) and have sufficient fitness for
- Must have adequate sensory ability (sight, smell, hearing, touch).
- Must be of an appropriate weight for the age, sex, and time of year.
- Must have a satisfactory hair coat.
- Must show appropriate wariness of humans and domestic animals.
- Appropriate health checks should be carried out prior to release. A careful
assessment (risk analysis) must be made as to the risks of released animals introducing
novel pathogens (disease agents) into the wild population/environment.
- These pathogens may have been acquired from domestic animals, other wildlife casualties
or humans whilst the animal was in captivity.
- The health checks should be designed to
minimise the risk that pathogens posing a threat to wild populations of this or other
species will be introduced into the environment when the animal is released.
- Hedgehogs should always be released unless disabled.
- Hedgehogs must be able to roll up tightly, and have a full coat of
prickles, when they are released.
- Hedgehogs have a particularly high incidence of periodontal disease. A dental
examination under general anaesthesia may be appropriate with cleaning and treatment as
required prior to release.(B151,
- Consider having a blood sample evaluated for detection of problems not visible by
- Consider providing natural food items as part of the
diet prior to release. (D78)
- Weigh before releasing. Hedgehogs require sufficient energy (fat) reserves if they are to
survive hibernation. Suggested minimum release weights are:
- Mid-summer: 450g, to end November, 500g, to middle of December, 600g. (B151)
- Minimum 600g (1 1/2 lb) in autumn for juveniles. (D78,
- Note that an adult weighing only 600g would be very thin and would
be unlikely to have sufficient fat reserves for hibernation.
- DO NOT RELEASE IF:
- Severely disabled, unable to curl up properly or lacking a full
coat of spines.
- Less than eight weeks old.
- Weight is less than 600g and the hedgehog will need to hibernate
Timing of release:
Hedgehogs should be released in the evening (at
dusk or just after dark). (B151,
Mild evenings are best for release. (D106)
Warm damp weather is preferable in summer
as more food (e.g. earthworms) will be available than during dry
- It has been suggested that hedgehogs should not be released between mid-December and
- If releasing in winter then mild weather is best; a
time without snow and without severe frost must be chosen. (D78)
- Hedgehogs may be better overwintered in a safe area with appropriate hibernation
facilities than released in winter when finding an appropriate place may be
- It has been suggested that overwintered animals becoming active before late March and
weighing more than 700g should be fed only minimally, encouraging
resumption of hibernation. This reduces the risk that they will
become sexually active too early and become restless in captivity,
as well as reducing the risk of obesity. (J147.3.w1)
- In spring hedgehogs should not be released until wild hedgehogs in the
area are known to be active and invertebrate prey items (e.g. worms,
slugs, beetles) are active at night. (J147.3.w1)
- DO NOT RELEASE in frosty or drought conditions, when the ground
is very hard, or when it is very wet and the released animal may have
problems finding dry bedding to make its nest. (B337.2.w2,
Selecting a release site:
- If the site of origin is known and is suitable (NOT e.g. a main road),
the hedgehog should be released back to the same place. (D106)
- In suitable habitat as suggested by the presence of other hedgehogs.
- e.g. in deciduous woodland or with access to 10 or more gardens.
- Pastureland, moist deciduous woodland, large
cemeteries and areas with gardens are good sites. (D78)
- The area must provide suitable nesting materials
(fallen leaves) and sites for nest construction (hedges, brambles or
- Avoid repeated releases at the same site. (B337.2.w2)
- Releasing back into the area of origin reduced the risk of the
hedgehog encountering a new disease, or of introducing a disease
into the release area which was not there previously
- Release sites should be of a similar habitat type to that in which the
individual was found e.g. suburban hedgehog released back to suburban not rural area.(V.w5)
- Away from major roads (e.g. "A" and "B"
roads) and busy railway lines as far as possible.
- If a lactating female is presented as a casualty but its condition is not
serious, release at the site of origin within 24 hours has been suggested so that the
female may return to her litter.(B151)
- The site of release should be recorded clearly (e.g.
street name and house number, Ordnance Survey map reference if
- For release of a litter of hand-reared hedgehogs it has been suggested
that the chance of most of the animals immediately dispersing may be
reduced if only one individual is released at any one site. (B337.2.w2)
- UNSUITABLE sites include:
- There are no other hedgehogs present: there will be a reason why
apparently suitable habitat is not actually suitable.
- There is already a very heavy hedgehog population.
- Gardens in the vicinity are known to contain dangerous dogs,
use molluscicides or have ponds without hedgehog escape ladders present.
- A badger colony or other predators are known to be nearby.
- It is fully enclosed (e.g. a walled garden) and the hedgehog cannot easily leave, as there may be insufficient food
- An island, as this may
not provide enough food and introduced hedgehogs on islands can upset
the natural balance of life on the island.
- The ground is waterlogged or likely to become
so in winter. (D78)
Type of release:
- Hard release techniques are normally used for adult hedgehogs.
- Release in the evening.
- Release under a hedge for cover.
- May be released via a suitable nest box (or e.g. a sack
of hay), leaving the box for use by the
- May be marked prior to release, using methods such as
paint, shrink-fitted plastic tubing, or ear tag.
- For hand-reared juveniles supplementary food should be provided following
release; this may also be provided for adults.
- A box with suitable bedding should be left at the release site providing
shelter for the hedgehog.
- Release at dusk to give the hedgehog the whole night for exploring and
- Continue providing food until the hedgehog stops returning (individual
marking e.g. with coloured markers on spines is required to identify that the hedgehog
eating the food is the one just released).
- Food can be protected from cats by being offered under an
upturned plastic box,
weighted with a stone or brick and with a hole in one side sufficiently large for the
hedgehog to enter and leave comfortably.
Monitoring after Release:
In order to allow monitoring after release the hedgehog needs to be
marked, for example by paining spines with quick-drying non-toxic paint,
sticking coloured beads to the spines, or using ear tags.(B337.4.w4)
Results of Release Studies:
Several studies have been carried out regarding
post-release survival and/or behaviour of hedgehogs. Very useful data has
been obtained from radio-tracking studies. Data has also been obtained
from sightings of hedgehogs marked prior to release. (P37.2.w1)
- Studies involving colour-coded pvc tubing on spines have shown
survivorship up to five years in Dresden. (P37.2.w1)
- On Jersey (Channel Islands, UK) hedgehogs have been marked with ear tags prior to release
and monitored on an ad-hoc basis by chance sightings of hedgehogs in
the wild (alive or dead) and by re-admission to the rescue centre at a
later date. Survival of at least five years has been recorded. (V.w56)
- A pilot study involved four hedgehogs fitted with
radio transmitters and released into an area known to provide good
hedgehog habitat (Malham in Yorkshire, UK). The release took place
during dry weather when food availability may not have been optimal.
One male became lethargic after release and died just six days after
release; the reasons for the death were unclear. The other animals
showed an ability to build and return to nests, travelled distances
comparable with wild hedgehogs in similar (woodland) habitat (females
(no. 225 and 255) about 500m per night, over about three hectares,
male (no. 275) average 795 m per night, over about six hectares). The
range used did not increase greatly after the first seven nights
although some new areas were explored. All three were observed
foraging and locating natural food, however the male lost 100g
(compared to weight of 1kg 24 hours post release) while the females
lost 6% of 760g (no. 225) and 35% of 685g (no.255) respectively.
None of the hedgehogs used dog food provided at the release site. The
male was observed courting wild females and spent a considerable
amount of time in this activity. When after 13 nights the females were
moved more than 0.5 km to sheep pasture, their nightly travels
increased. Female no. 225 moved back, overnight in unfamiliar
territory, to near her previous location and when moved again returned
once more, directly to her original nest. Female no. 255 wandered more
and was last seen in a small plantation area, with a male hedgehog. (P13.3.w1)
- Eight rehabilitated adult hedgehogs were released
onto farmland, in an area known to support hedgehogs, in warm dry
weather (not sufficiently dry to cause food shortages). The hedgehogs
were monitored closely for the first three weeks then four weeks later
were followed up. One animal became ill and died, possibly indicating
premature release. One animal became entangled (transmitter caught on
grass and brambles) and was fly-stuck, but was rescued, cleaned and
re-released. The hedgehogs tended to lose a little weight initially
then maintain or gain weight slightly. By the end of the first three
weeks seven animals were still alive. Normal behaviours were noted
such as courting, nest building, returning to a previously used nest
and establishing a home range. There were no aggressive interactions
noted with resident hedgehogs. Most scattered from the release site.
At least six were still alive after five weeks. At least three were
still alive after seven weeks and had gained weight. and a probably
three others were reported by members of the public at sites 2- 4km
from the release site. By eight weeks in addition to the one which
died from illness one had drowned and another been killed by a car;
one was known to be still alive and four were unaccounted for; it was
considered unlikely all were dead. (J147.2.w1)
- Twelve juvenile hedgehogs, with little or no
experience of life in the wild before being rescued, were released in
pasture land in Devon and monitored nightly for five weeks. Six were
"hard released" and six "soft released" after five
nights in small cages at the edges of the fields. Three made
dispersal movements after several nights. Substantial weight loss
(e.g. 20-30%) occurred initially, particularly in the heaviest
(overweight) animals; weights stabilised after about one month.
Animals rapidly learnt their way about the area, foraged effectively
on natural foods, built nests and returned to them and interacted with
other hedgehogs. Three females were found to be pregnant 26-49 days
after release. One animal was euthanased after 17 days due to illness,
three were predated by badgers after surviving for five weeks and two
was killed by cars after five days and four weeks respectively. Four
were known to survive to the end of the study and two until their
radios were lost after three and four weeks. The study was
interpreted as showing that juveniles without previous experience
could survive after release. The hedgehogs did not show regular use of
the pre-release cages after release. (J147.3.w1)
- Pre-release health checks in these animals
revealed problems of periodontal disease and bite injuries from
other hedgehogs. The animal euthanased 17 days after release had
parasitic bronchitis, verminous gastroenteritis and chronic
interstitial nephritis. One animal had died while anaesthetised
prior to release; it was found to have chronic lung abscessation,
bronchopneumonia and chronic low-grade myocarditis. The hedgehog
killed by a car four weeks after release had shown weight loss; on
necropsy it lacked subcutaneous or abdominal fat and its stomach
was empty; failure to thrive may have increased its chance of
being run over. Animals were overweight prior to release; this may
give a "buffer" during the period after release when
learning to forage effectively. There was no evidence that the
release caused adverse effects in the local wild hedgehog
- A study involving eight rehabilitated hedgehogs
released into a reserve found that six of the hedgehogs were lost
within a week, mainly or totally due to predation by foxes. This study
showed that the site, although apparently suitable habitat, was not
an appropriate release site. A different site was then chosen and
further radio-tracking studies found that all hedgehogs which were
successfully tracked survived for the two-month period of the study. (N6.33.w1)