Talk notes:Hedgehogs

Dr Phil Baker, from Reading University, gave us a fascinating talk on hedgehogs recently.
 
We learnt that there are 4 species of hedgehog in Europe, with slightly overlapping ranges in some areas, although there is only one native wild species in the UK (in addition to pet hedgehogs which are of a different species). Hedgehogs belong to the order Insectivora but are actually omnivorous and a highly adaptable species, which evolved in woodland edge habitats about 15 million years ago. They usually have 1 litter a year, although occasionally have two, and hibernate through the winter prompted by cold temperatures. Their main food sources are earthworms and insects, but they can also eat some terrestrial molluscs and eggs of ground-nesting birds. Their average life-span is 3 years although the record is of a 16-year-old hedgehog.
 
It is very difficult to know exactly how many hedgehogs there are, the extent of their decline and the reasons for their decline but there are a few known facts known through different sources. However, Phil pointed out more research is needed on all aspects.

Hedgehogs were abundant in the past, and were particularly favoured by the Enclosures Acts, which created lots of hedgerows, in the postmedieval period. Hedgehog populations started to fare badly with the popularisation of game shooting, and as possible predators of ground-nesting game bird eggs and chicks, they were routinely killed by gamekeepers. They could have gone extinct if it hadn’t been for WW1. Since WW2, numbers of hedgehogs have steadily decreased (estimates range between a 50 and a 90% reduction).
 
A series of circumstances are liable to the decrease in the number of hedgehogs and their admittance to rescue centres (which on average have a 50% rehabilitation success):

Human causes

• Roads
• Harmful behaviour:
  • Indirect/unintentional: poisoning, pollutants, littering (including mail elastic bands), netting, bonfires, strimmers, ponds with no ramps, overfeeding/misfeeding by caring humans…
  • Direct/intentional: kicking, shooting…
• Agricultural
  • Habitat destruction: Disappearance of hedgerows
  • Food scarcity:
    • Application of insecticides - not enough insects left.
    • Soil compaction due to heavy machinery - no access to earthworms.
• Climate change:
  • Hedgehogs are not fattening enough to survive the winter due to too hot summers, which reduce food availability.
  • Hedgehogs may see their natural life expectancy reduced due to lack of hibernation, although few hedgehogs reach old age.
    

​Natural causes

• Parasite infestation (internal and external)
• Interactions with other wildlife:
  • Badgers and foxes compete for the same food as hedgehogs, but 1 badger eats the same amount of food as 7 hedgehogs!
    • Increase in badger numbers can effectively displace hedgehogs from habitats, due to the hedgehogs’ avoidance of badgers.
    • Badgers and foxes can occasionally predate on hedgehogs but the numbers of hedgehogs killed by dogs is estimated to be higher than those killed by badgers or foxes.

Over the last few years, a series of charities and conservation organisations have promoted measures to promote hedgehogs, such as hedgehog houses and hedgehog tunnels. These have had mixed success, while it shows some people are really enthusiastic about hedgehog conservation, it is not enough people and significant achievements have not been obtained. Wildlife rehabilitation centres are increasing in number and capacity and there is evidence that they can be a factor in slowing down the rate of decline. Thus, hedgehogs may actually go extinct if we don’t change enough decline factors.
 
To end on a positive note, I want to highlight the following positive actions out of Phil’s talk:

• If you feed hedgehogs:
  • Feed the right food: do not use milk (of any kind), mealworms or nuts.
  • Don’t overfeed them, as they can be discouraged from hibernating or moving across the landscape and therefore encountering other hedgehogs and reproducing, also they can get obese and be unable to curl into a ball to protect themselves from predators.
  • Try to avoid interactions of multiple animals and species at the same feeding stations to avoid disease transmittal and direct attacks, including from hedgehog to hedgehog. If you use a feed box, make sure it has two holes!
• Do not be responsible for possibly harmful behaviour:
  • Do not use rat poison boxes: juvenile hedgehogs are small enough to get in and hedgehogs of all sizes can get secondary poisoning from eating invertebrates that have fed or even just walked on the poison. If you have a rat problem, please use alternative methods.
  • Before strimming or lighting bonfires, check for hedgehogs.
  • Do not abandon any litter and pick up any litter, particularly food/drink containers, elastic bands, rings or netting
  • Do not replace vegetation in your garden by plastic grass, decking or paving.
  • Do not completely fence your garden, leave some small gaps for a hedgehog to get through.
• Talk to your neighbours and spread the word.

​Inés López-Dóriga