3/5/2016

Understanding a prickly subject

By Jonathan Reynolds, GWCT Head of Predation Control Studies

HedgehogThe hedgehog is one of those animals that seems to belong in the British countryside by ancient right. They are embedded symbolically and sentimentally in our culture, and it is easy to see why they remain popular.

In evolutionary terms, the world’s spiny hedgehogs have changed little in the last 15 million years. If you think of that as a day, modern man appeared about 10 minutes ago, agriculture less than a minute ago, and the last 100 years occupied the last half-second. Given that the hedgehog ‘formula’ developed in a world radically different from that of today, it is astonishing that they persist at all.

Nevertheless, within living memory hedgehogs have been – and in some parts of Britain remain – a very successful species. For instance, a study in north Norfolk in 2008 found a density there of more than 40 per 100 hectares.

Hedgehogs are a component of the farmed landscape that the GWCT has scarcely considered before, but ecologically they are at the heart of ‘hot’ countryside issues. The invertebrate creatures that form the bulk of their diet are affected by the intensity of modern agriculture, making an obvious parallel with farmland birds.

Agri-environment schemes to mitigate this impact potentially benefit hedgehogs just as they do farmland birds; and indeed hedgehogs have been shown to favour grassy field margins in an otherwise intensive arable landscape. But dead hedgehogs cannot benefit, and there is known to be a strong negative relationship between badger density and hedgehog density; foxes, too, can learn to kill hedgehogs.

Then again, hedgehogs are predators themselves. Predation by hedgehogs on the eggs of ground-nesting wading birds is the reason they are being removed systematically from the Outer Hebrides (where they are not native) and transferred to the mainland.

When hedgehogs were more common on the mainland, they were killed on shooting estates as predators of wild gamebird eggs, and thus were routinely recorded in National Gamebag Census data. Both the number of estates recording hedgehog catches and the numbers reported have fallen dramatically since the early 1960s.

The Wildlife & Countryside Act 1981 ruled that hedgehogs may not be deliberately trapped, though unless measures are taken to exclude them they can still occur as a by-catch in tunnel traps. Regrettably, we cannot distinguish to what extent the trend in NGC records indicates a declining hedgehog population, lower trapping effort, more focused trapping, unwillingness to record hedgehog captures, or all of these effects.

There is nevertheless a widespread perception that there has been a decline in UK hedgehog numbers in recent decades. As with many other mammal species, there is no routine surveillance system, and no established method to determine distribution or population trends. There have been questionnaire surveys, and systematic recording of road kills.

The People’s Trust for Endangered Species has mapped hedgehog distribution through questionnaire surveys to householders. This has told us a lot about the national distribution of hedgehogs in gardens, but inevitably it also reflects the distribution of people in Britain.

Trends in the number of hedgehogs killed on roads are complicated by traffic density and speed and by shifts in recorder enthusiasm. In either approach, the 70% of Britain’s land area that is agricultural is essentially unsurveyed.

The University of Nottingham, in partnership with the Mammal Society, has researched the use of simple ink-and-paper tunnels to detect the presence of hedgehogs by recording their footprints. This provides a cheap tool to help determine hedgehog distribution, and potentially an index of abundance too.

Hedgehog MapFig 1 - a night’s movements by an adult male hedgehog during one April night,
around houses that 
stand adjacent to arable farmland in Wiltshire.

So hedgehogs present themselves as a component of the farmed environment in which the GWCT should take an interest. As opportunity and resources allow, we have made the decision to do that. We believe that we have something to offer, both in further developing the detection methodology (much as we did in the context of mink control), and in establishing what is happening to hedgehogs in the farmland landscape.

Is there a decline? And if so, is the cause a shortage of invertebrate food, or predation, or something else? Why do hedgehogs appear to favour gardens, even in the middle of farmland (see Figure 1)? How can we best manage farmland so as to achieve the most satisfactory balance between all our native species?

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Comments

Hedgehogs and badgers

at 15:06 on 02/06/2016 by Brian Copestake

It is highly probable that badgers are a major contributor to the decline of the hedgehog. Question is, why have badger numbers increased so much in the last two decades or so? It so happens that the maize acreage has expanded at the same time, coincidence? Badgers love to feed on ripening maize cobs not only in the field but also in the clamp, thus going into and through the winter in peak condition. Now maize is being used extensively in AD plants in the east of England, it will be interesting to see if badger numbers increase and hedgehog numbers decrease in these 'new' maize areas.

Hedgehogs

at 15:10 on 13/05/2016 by Jodie Twose

Absolute value in surveying the wider countryside but you are verging onto seriously dodgy territory to start suggesting badger predation is to blame. If two species have coexisted in ecological harmony for hundreds of thousands of years, you have to ask yourself what changed to tip that balance. As you well know agricultural intensification and urbanisation are two such changes and it would seem that a failing countryside is failing to support two species which largely rely on the same food source, 'invertebrates'. In addition loss of hedgerow and grasslands have been huge factors as well as fragmentation that have all contributed to the decline of hedgehogs. Hence why hedgehogs have moved into our gardens, a place that now supports more invertebrates than our arable fields (at least for the time being), chemical overuse may even change the ability of gardens to provide ample food in the future! I'm personally very interested in any research you choose to conduct in this area, but please be very cautious of opening up a dialogue that once again sees badgers being made the scapegoat in what is an extremely complex ecological relationship.

Hedgehogs.

at 20:16 on 11/05/2016 by S. H. Polglase.

I live on a small holding of 14 acres in the far west of Cornwall. The holding has been in my family for many generations and has always had a low density of cattle running on the fields. The fields on the property have never been subjected to agricultural sprays and the surrounding countryside the same as it is not subjected to intense agriculture. Until about ten years ago we had a reasonable population of hedgehogs but since then have seen a steady decline to the point where I have not seen a hedgehog alive or dead as road kill in the last two years. My ground is on the edge of the Godolphin estate which is owned by the National Trust. The estate has a large population of badgers, one sett 100meters from my land. The badger population has risen many fold here since the early 1970s as has the incidence of TB but that is another story. I have a friend who spends many hours at night culling rabbits and foxes professionally. and has seen on many occasions badgers rolling hedgehogs over and unrolling them with their claws and then eating them so I am convinced this is the reason for their decline.

Hedgehogs

at 18:17 on 11/05/2016 by Mary Gray

We moved to the South Lakes, Cumbria in 2000. There were very few badgers here, but numerous hedgehogs. Now we are inundated with badgers and very rarely see a hedgehog!

Hedgehogs

at 12:26 on 11/05/2016 by Jeremy Scott_Bolton

You did not mention the predation of hedgehogs on badgers. I live in the badger cull zone in West Somerset and since the cull have started to see dead hedgehogs on the road something I have not seen for years. Would it not be a good idea to survey an area before the cull and continue to monitor it to see how the hedgehog population recovers?

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