This one causes a lot of arguments so this is the bottom line as agreed by the Hedgehog Researchers across Europe, the British Hedgehog Preservation Society, the British Wildlife Rehabilitation Council, the RSPCA Wildlife team, and applies to healthy hedgehogs out and about in winter, not hedgehogs that are obviously injured or collapsed. If in doubt call a LOCAL rescue for advice.
Dr Pat Morris states that in tests performed in a laboratory in Germany, any hedgehog under 450g will not survive hibernation and therefore that is the weight we quote as the ABSOLUTE MINIMUM WEIGHT AT WHICH THEY WILL SURVIVE  but, that is not the ideal.
At 450g they wake up but that does not mean they have the energy to go and get food and water. Most Rescues will take in hedgehogs under 600g WHEN THE GROUND IS COMPLETELY FROZEN OR FORECAST TO BE SO which means they will be unable to dig for food. Short periods of cold weather where the ground doesn’t freeze do not necessitate capture unless the animal is unwell, just put out food and water daily.
Taking in hedgehogs over 600g can do more damage than not as the stress of captivity can affect their immune system allowing parasites they would normally be able to deal with in the wild, to become rampant and require intensive treatment. Over 600g just provide food and water right through the winter. Make sure there is plenty of dry garden waste around for them to make an insulated nest then just monitor from a distance.
This, as stated before, is the current stance of the BHPS, the researchers and the large rescues. What is causing the disagreement is newer rescues and well-meaning members of the public adding 50g here and there “to be on the safe side”. This has resulted in some people saying 850g needs to be brought in which is mad especially with warmer winters allowing us to release 700g hogs in mild spells where night temperatures (3am) are above 5°c.
For those now wondering about what food to offer:
- Tinned cat or dog food, any flavour including fish is fine just check for bones.
- Cat dry kibble any flavour including fish.
- Proprietary Hedgehog food as long as it is just the kibble and not heaving with weird additives such as dried banana or any of the other no-nos mentioned below.
- Hedgehogs need nutrition not treats.
Fish flavours are absolutely fine if that is all you have to hand. We regularly feed fish flavours for two reasons.
- That’s what people donate.
- Hedgehogs with nasal injuries can smell it better.
It does not cause them issues any more than any other change of food will. Most pet food is bulked out with fish meal anyway even if it says Chicken on the pack.
DO NOT GIVE;
- Please do not give treats
- Mealworms, peanuts, or sunflower hearts, all of which can cause Metabolic Bone disease .
- Peanuts can also become wedged across the roof of the hedgehog’s mouth preventing them from eating. Peanuts should only ever be put out in wire bird feeders so the birds peck small bits off.
- Sultanas, fruit, cake or sweet biscuits which cause tooth decay and NO MILK OF ANY KIND EVER!
 British Hedgehog Preservation Society, Vale Wildlife Hospital, British Wildlife Rehabilitation Council, RSPCA. (2015)
HEDGEHOG HIBERNATION WEIGHT – A COLLABORATIVE VIEW. https://www.britishhedgehogs.org.uk/pdf/Hibernation-Weight.pdf
 Vale Wildlife Hospital Tim Partridge B.V.Sc., M.R.C.V.S. (2016) Metabolic Bone Disease