Releasing captive hedgehogs into the wild

BHPS know your hedgehog Series

The problem

When, for some reason or other, hedgehogs have been kept captive, a time generally comes when they are ready for release into the wild.  When? How? Where? These are the questions many people want answered and we thank Dr Pat Morris and Randalls Wildlife Rehabilitation Centre for providing the following answers to such queries.

A caution

The suggestions offered are based in part on impressions gained from three field studies where hedgehogs were released and subsequently radio tracked for two weeks or more.  One study was in an area of deciduous forest in Surrey; the animals were let go in the woods in July after several weeks of dry weather.  The other studies were in farmland (pasture, arable fields and hedges), also in dry July weather.  The collation of information on hedgehog release into the wild is continually being updated.  It is already clear that each hedgehog behaves differently and some may adapt to the wild faster and better than others.  The following are some of the questions we are most frequently asked:

  1. Do the hedgehogs fail to find adequate food in unfamiliar surroundings, having been used to getting it from a dish?
    No: they lose weight initially, but after a few days regain it and therefore maintain a normal body weight.  It’s an excellent idea to try to introduce ‘natural’ food into your hedgehog’s diet prior to release (e.g. worms, beetles, etc).  He won’t always eat it but at least he may remember the smell.
  2. Do they tend to ‘home’ towards the place where they had formerly lived?
    No: they quickly become accustomed to their new surroundings and soon are travelling similar distances at night to the wild hedgehogs that live in the same area.  (However, a couple of animals in one of the studies carried out by Dr Pat Morris failed to adapt and just stayed in their nest for days).
  3. If they build a nest can they find their way back to it over unfamiliar ground?
    Yes: they continue to use the same nest or move to another, just as wild hedgehogs do.  There is probably little point in trying to build a nest yourself for the animal to use.  Hedgehogs are better at nest building than we are and the chances are that they will locate a better place to live than the one provided.  You could still try though – there may be a shortage of nest sites in the locality.  Or perhaps better still, leave a small bundle of dry leaves or straw near to your hedgehog’s release point.
  4. If they find a garden with cat or dog food put out for hedgehogs will they stay there and become dependent upon unnatural food as in their captive life?

    No: probably not.  Wild hedgehogs use plates of cat or dog food and other tit-bits left by caring humans as a supplement to their natural food, not a replacement for it.

  5. Should food be put out at the release site?

    Can’t do any harm, but it is not essential, especially if you have managed to adjust your hedgehog’s diet to include natural food.  In very dry weather water should always be left near the release site.  for hedgehogs released in the garden the best thing would be to leave their cage or pen open, with food in it, and have the door open so that the hedgehogs could return to feed or use their old nest box if they wished.

  6. What is the best time of year to let them go?

    In winter choose mild, muggy weather if possible; avoid periods of snow and especially severe frost.  In summer, any time but warm moist weather is best; rainy weather is better than dry because there are likely to be more worms and similar food easily available than in dry periods.  Aim to release your hedgehog at dusk as this is when they would normally awaken from daytime sleep in the wild.  This will then give your newly released charge the benefit of the cover of darkness to root around and become acquainted with his new home.

  7. Where is the best place to let them go?

    Research your site carefully.  Choose places where there are likely to be hedgehogs already (no evidence that wild ones will ostracise the released animals).  Parks, recreation grounds with nearby gardens, big cemeteries, lush pastureland, moist deciduous woodland are good places.  Conifer woods, moorland, arable farmland, open bracken covered hillsides are bad sites.  DO NOT pick a place that is likely to be waterlogged in winter, even if it looks suitable in summer, unless there are nearby areas of well-drained land adequate for winter nesting.  Ensure there are no busy roads or even railway lines close by and that local farmers in the vicinity of the release practice organic farming. Also bear in mind that slug bait and pesticides in gardens can prove fatal to hedgehogs.

    Hedges, thickets, brambles and dense cover are needed for siting winter nests; plentiful fallen leaves are essential for nest construction.  Straw, grass, dried bracken are suitable nest materials in captivity (so is newspaper), but not very good in the wild being insufficiently weatherproof. 

    Hedgehogs should not be released into areas with no natural hedgehog population or into enclosed areas as they travel about a mile each night and a healthy hedgehog is likely to become very stressed if enclosed.

  8. How far do I need to take the hedgehogs from a road to be sure they won’t get run over?

    Hedgehogs regularly travel upwards of a mile a night and it is difficult to find anywhere in lowland Britain more than a mile from a road.  Country roads are just as dangerous as well lit busy town ones.  Once the animal has been released it will have to take its chance, just as wild ones do.  Dangers can be lessened (see answer to question number 7); small roads with little traffic and suburban roads with slow traffic may be less hazardous; also ensure that release is into a large habitat area (e.g. several acres) so that there is less need for the animal to leave it and seek more space and opportunities elsewhere.

  9. Do not take hedgehogs to islands (or other isolated places) with the idea of stocking up a new habitat or giving them a place to themselves.  This may be illegal and also cruel if the site turns out to be insufficiently large or rich enough in food.  Very little research has been done on this sort of thing and so we don’t know what is too small an area; in any case it will depend upon habitat type.  But we do know that taking hedgehogs to an island can upset the fragile balance of other forms of wildlife.

A reminder

Hedgehogs should never be released into the wild in Autumn unless they weigh more than 1.5lb (600g) and are fully fit.