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Hedgehogs: Beating the odds

Updated Monday, 26th April 2010

Hedgehog ecologist and campaigner, Hugh Warwick, talks to the Saving Species team in an extended interview, and offers an insight into the world of hedgehogs; from mysterious corn circles to marauding badgers.

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Copyright The Open University


Presenter: What is a hedgehog and how do they fit within the British small mammals?

Hugh Warwick: Hedgehogs are insectivores. They’re one of the same group of animals such as moles and shrews and things like that. Now they often get lumped together with other spiny mammals, like porcupines, which is, and people will say surely therefore they’re the same as porcupines but porcupines are rodents like mice and rats. So they’re a different sort of mammal. They belong much more closely with things like the shrew and the mole.

Presenter: And are they found all over the world?

Hugh Warwick: The range of the hedgehog is quite an old world species. They range from the West Coast of Ireland across to the East Coast of China and down through Africa to South Africa; that’s their sort of natural current range. But there are hedgehogs in New Zealand, surprisingly. There were some European hedgehogs taken out there in the 1850s by the Acclimatisation Society, a bunch of people who thought when arriving in New Zealand ‘gosh this place is gorgeous but it’s missing something’.

Presenter: And the European hedgehog, how widely distributed is that?

Hugh Warwick: The European hedgehog, what we have in the United Kingdom is Erinaceus europaeus, the Western European hedgehog, and when you get to about the Czech Republic you start to get the Eastern European hedgehog. They stretch all the way across Europe and the two species, in the last big Ice Age there’s thought that they were pushed far south into two different pockets, and they then speciated in these different pockets, and then as the ice retreated they moved back up through Europe getting further and further north and becoming sort of a separate species. The Western European hedgehog, we’re sort of right at the westerly end of its range.

Presenter: Could you take me through a hedgehog year?

Hugh Warwick: We could start with about now, I mean this is April, early April at the moment, they’re coming out of hibernation. This is the end of this great period of dormancy which they go through. Now hibernation is fantastic. The hedgehog’s metabolism shuts right down, they pretty much stop breathing. Their heart beat is down to just a few beats per minute. So in spring the hedgehogs are emerging, coming out of hibernation.

They are hungry, they haven’t eaten for many, many months, and also it’s the time to start trying to reproduce. It’s time to find a mate. So the male hedgehogs tend to emerge slightly earlier. They eat a little bit and then they spend some time snuffling around, trying to find females as they emerge from hibernation, and then they’ll loiter around and they’ll wait for them to come into season. Then there is a little courtship which is a fantastic affair. If you get a chance to watch hedgehog courtship, it’s a spectacle.

It actually led to the best ever headline I’ve ever seen in a newspaper which was, it was in the Guardian, ‘Hedgehogs Cleared of Corn Circle Dementia’, because they will literally create a little corn circle with the female in the middle trying to keep facing the male who’s going around the back trying to get behind her, and every now and then she does this little explosive noise, she goes pfft pfft and jumps forward and the male jumps back and they go, and this can last for hours. And they will flatten a circle of grass, an arena which can be up to a metre or so across.

So after that, about six weeks later, you’ll get some young hedgehogs emerging, probably five or six per litter will be brought up just by the mother, and then six weeks later she’ll kick them out. There’s some thought she may then go on possibly to have a second litter, but that’s contentious. These young hedgehogs have the big job of trying to eat as much as they can so that by late autumn they can begin the process of going into hibernation and then the entire year begins again.

Presenter: Once, presuming this young hoglet then is off into hibernation, happily comes out the other side, how long can a wild hedgehog expect to live for?

Hugh Warwick: Well it’s interesting you describe it as the one that survived hibernation, something like a third of all hedgehogs don’t make it through their first year because a massive number are killed or die, rather, during hibernation. An old hedgehog will be six. So that gives you a rough idea. So once they survive the first year you can expect a hedgehog to live to three or four.

Presenter: And what sort of habitats do you find hedgehogs in?

Hugh Warwick: Hedgehogs are what you would describe as a woodland edge specialist. So originally they would have found their most favourites of habitat in clearings, in bits of subgrade forests that would cover the country. But now, well their name kind of gives it away, I mean the ideal habitat for a hedgehog is a hedge. I mean they’re an animal which is specifically designed to hog the hedges.

So that is where they’re most comfortable. It gives them that degree of shelter and protection which the hedge provides, but also the hedge is a biodiverse area. It’s a place which will attract invertebrate food sources so that the whole macro invertebrate fauna will congregate in a field sort of closer to the hedge. So there’s food and there’s shelter. So that is their favourite I’d say - rural habitat.

I would suggest possibly their favourite habitat of all is going to be, I don’t know, an organic sort of Surrey garden backing onto a big golf course, something like that. Again, it’s the same idea, you’ve got lots of difference of patchworks of habitat which, sort of, a hedge provides; you’ve got gardens fulfilling those needs.

Presenter: And what sort of things do wild hedgehogs eat and does that change through the season?

Hugh Warwick: A hedgehog’s main diet is probably sort of worms, caterpillars, slugs and snails. They will and have been rightly accused of eating birds’ eggs. And actually, the percentage of a hedgehog’s diet which is birds’ eggs is very, very small; however, the bird’s eggs are only around for a short period so it can have an impact, hence the reason why there have been sort of conservationists controlling hedgehogs in the Outer Hebrides.

But yes I mean they are insectivores, they don’t just eat insects obviously because they are eating things like worms but it is that sort of beast. It’s going to be obviously quite slow moving because they’re not very fast themselves. Although they’ve been known to tackle sort of nests of mice and they’ll take nestlings occasionally.

Presenter: I have heard, and I don’t know whether this is true, that they don’t get along too well with badgers, is that actually the case?

Hugh Warwick: Badgers and hedgehogs have a complicated relationship. Badgers and hedgehogs are competitors for the same food resource. They both eat worms and slugs and snails. The problem in terms of competition is that a badger is much bigger; they will eat approximately the same amount of food as seven or eight hedgehogs.

So if you’ve got a limited food source then the badger will sort of hoover it up far more effectively than the hedgehog, the hedgehog will suffer, will be eating less. If this food resource, and this is the theory we’re developing at the moment in sort of conservation groups, is if this food resource is denuded in any way, if there are less worms, if there are less beetles, in the field margins, for example, the relationship between badgers and hedgehogs changes from one of competition to one of predation, and obviously it’s going to be badgers eating hedgehogs. The tales of packs of hedgehogs bringing down an adult badger are I’m afraid a myth.

If badgers are having an effect on hedgehogs at a population level what can we do about it? And it seems there is a correlation, at the moment it is just a correlation, between presence of badgers and absence of hedgehogs. We don’t know that it is causal but we think it probably is. And then it leaves us with the problem, we can’t exactly call for a cull of badgers to protect hedgehogs can we? So it makes it difficult. What it does result in is an increased importance for the refuges, those areas, for example, in villages, in rural areas, where hedgehogs still are plentiful. It increases their importance because they are refuges from potential predation by badgers.

Presenter: Hedgehogs aren’t doing that well in the UK are they? So can you tell me a little bit about what the problem is?

Hugh Warwick: Hedgehog population of the UK has been declining. We know this from a survey called Mammals on Roads which rather unfortunately is actually using corpses of hedgehogs to be able to assess the status of the hedgehog in the wider population. The more hedgehogs you see dead on the roads actually means the more hedgehogs there are in the environment; it doesn’t mean you are wiping out the hedgehogs in the environment. And from this we’ve seen a steady decline in the numbers of hedgehogs. Between 2001 and 2005, mammals on roads showed a 20% decline in hedgehog population; other surveys have shown bigger declines. And we’ve got ongoing monitoring around the country because it’s now reached a status of a priority species on the UK Biodiversity Action Plan which is, which means it’s now recognised.

Okay this very widespread, this very charismatic – in fact many people think very common – species is under threat. And it’s not like we are going to see the extinction of hedgehogs in the United Kingdom in any near time but we are going to it seems to see pockets of hedgehogs, more sparsely populated throughout the country. These will be little islands almost because it seems the biggest threat that hedgehogs face is habitat fragmentation; that they are being left in a pocket of gorgeous suburbia without too much decking, too bigger fences and patios, and they’re been left in a village surrounded by hedgeless fields and lots of marauding badgers, and they’re being left in a bunch of allotments which are all organic.

But we are blocking their ability to move between these areas; the hedges are going down, the roads are getting busier, something like a 5% per year increase in traffic on the roads, all of these things obstruct and prevent hedgehogs from moving into habitats, new habitats. So that when, I don’t know, the badger takes the last breeding female in that pocket over there it means they’d quite like to have another female, it’s not like the bush telegraph and they say send some females, but hedgehogs will move on and if they find a space where there is a niche for them they’ll settle down. But if they can’t get there those little areas are going to be subjected to attrition and eventually extinction.

Presenter: And is there any evidence that chemicals in agriculture have any kind of adverse effect on hedgehogs?

Hugh Warwick: I’m frequently asked about slug pellets in particular because people are very worried about the impact this may be having on hedgehogs. Well you have to feed an awful lot of slug pellets to a hedgehog to kill it. Now what we don’t know is what sub-lethal effects exposure to slug pellets have because it’s very difficult to measure that sort of thing, and so this is something which we’d love people to start investigating. But it seems that, my understanding the biggest threat that hedgehogs face from broad use of molluscicides is it wipes out hedgehog food. Because there are certain marauding, evil spawn of Satan slugs which will take away your seedlings.

But there are a whole bunch of slugs out there which are absolutely essential for the maintenance of soil quality, they’re the detritivores. They don’t take green shoots, they take the old leaves and they turn them into soil. Now the hedgehog eats both, and if we remove an entire range of hedgehogs’ food by smothering a place in chemicals then the hedgehog is going to have less to eat. Interestingly so are the badgers. The badgers will have less to eat, so therefore the badgers will be more likely to turn to predation rather than competition with the hedgehog. So it’s a bit of a double whammy for the hedgehog.

Presenter: And what needs to be done now to sort of find out where we are with hedgehogs, whether they’re still in decline but also to help them?

Hugh Warwick: At the moment I’m working with the People’s Trust for Endangered Species, the British Hedgehog Preservation Society, we’re looking at producing a UK hedgehog conservation strategy. We’re finding all the people who are doing key research on hedgehogs at the moment, and there are people all over the country doing that. We’re working with ornithologists, which over the years has been a sort of ornithologist/hedgehog sort of war going on because of concerns about eating birds’ eggs.

But actually the ornithologists have got so much data at their fingertips because they’ve got such a widespread and ready and keen body of people collecting it that we’re going to be able to use their data to help map the distribution of hedgehogs, to try and correlate the map of the distribution of hedgehogs to the sorts of threats that they’re facing, whether it’s badgers, traffic development, that sort of thing. And then when we’ve done that, and we’ve got this continual monitoring of mammals on roads, we shall be able to start to say well okay these are the key points.

Now we know the habitats need to be joined up, we need to make hedges more like hedges again. You can’t expect farmers to turn around and suddenly spend vast amounts of resources building proper hedges, even though there are various schemes trying to encourage people to do that. You can do it through dead hedging, getting branches, laying them along hedges, actually they will build up leaf litter; they will create an artificial hedge to a certain extent.

You can encourage people in suburbia to start taking down or at least making holes in fences to allow hedgehogs to move between gardens. You can encourage them to stop using quite so many agrichemicals. You can encourage them to, I don’t know, dig up the decking and smash up the patios to create a hedgehog habitat. Because what hedgehogs desperately need is somewhere to live, somewhere to move through, somewhere to feed and somewhere to shelter. And we can create that in our own gardens by being a little less precious and a little less tidy and just thinking a little bit more like a hedgehog.

Presenter: And the fact that the hedgehog’s now in the biodiversity action plan, does that mean that all of these things are going to be actively driven forward?

Hugh Warwick: The biodiversity action plan indicates a level of concern, what happens about it is up to, I guess, the hedgehog, is up to individuals really. As I say, I’m working with two different charities and we are doing the work ourselves; there’s no sort of government support in that. It’s what we can put forward, we can push people into doing, we can encourage people to focus their research in particular areas, we can produce information for ecological consultants who are liaising with the local authorities and with the planners to try and get new developments to encourage biodiversity in such a way as to improve the lot of the hedgehog.

We can do all of those things but it’s essentially up to us. It’s up to you and me to make our gardens as hedgehog friendly as possible, and it’s up to us to be able to spread the word about how best to improve the habitat for hedgehogs.

Hedgehog Copyrighted  image Icon Copyright: Flickr CreativeCommons elcasfoto

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