Tough times for Hedgehogs

It has been a long winter, not just for us but also for our mammals, birds and invertebrates. Some indication of just how late winter hung on this year can be seen in the later than usual sightings of spring’s first butterflies or the delayed arrival of our summer migrants (many of which are a fortnight or more behind what we would normally expect).

Perhaps the best indication of the what effects the winter has had on our wildlife comes from the BTO’s weekly Garden BirdWatch survey (www.bto.org/gbw). Each week throughout the year, the 15,000 participants chart the comings and goings in their gardens of birds, mammals, amphibians, butterflies, dragonflies and bumblebees. This community of ‘citizen scientists’ – as the Americans like call them – provides a fascinating insight into patterns of garden use, both between seasons and across years. The latest results from the survey show, for example, that the emergence of hedgehogs from hibernation is nearly a month later this spring that it was in either 2011 or 2012. Even the cold start to 2010 only saw hedgehog emergence delayed by a fortnight.

Of course it is not just a case of the hedgehogs emerging just a little bit late. A late emergence means more time spent in hibernation, placing greater strain on the energy reserves that were laid down last autumn. It seems likely that there will have been higher levels of overwinter mortality this year, something that may place additional strain on a population that is known to be in decline. It is not known just how many of our hedgehogs die during hibernation but mortality levels among young animals, born the previous summer, is thought to be high. A study in southern Sweden, where winter conditions are more challenging, found that just under a third of young hedgehogs entering hibernation failed to survive through to spring.

Newly emerged hedgehogs will need to feed up, replacing lost resources, before the breeding season starts in late April or early May, with the first young normally born in the last week of May. This year, however, I suspect that births will be delayed, shortening the amount of time that newly independent youngsters will have to fatten themselves up ahead of entering hibernation, something that can begin as early as mid-October. The first individuals to enter hibernation are the adults and youngster may remain active for longer, suggesting that they are still seeking out feeding opportunities and trying to achieve a body weight that will see them through the winter. Let’s hope that the summer is long and delivers good numbers of large invertebrates on which this year’s generation of hedgehogs can fatten themselves up. 

A price worth paying

The environment has been taking something of a battering over the last 12 months. It seems that when the economy is struggling, it is the environment that is one of the first things to suffer. In an attempt to reduce costs, cuts within Government and its agencies seem to have fallen hardest on those responsible for looking after the countryside. Elsewhere, in a bid to get the economy moving, there is talk of loosening planning legislation and weakening the already poor environmental regulations. Then there has been the criticism of conservation-based NGOs, often from within their own ranks, with the suggestion that such organisations have been all too ready to rollover.

For me, perhaps the most worrying thing has been the increasing tendency to put a price on the environment and its natural processes. This approach argues that we undervalue our environment and that, as a consequence, the best way to address this is to give a monetary value to each natural process, something referred to as ecosystem services. The ‘value’ of pollinating insects to UK agriculture has, for example, been put at £400 million per annum. In some ways I can see the benefit of this. By presenting wildlife ‘value’ in the monetary terms that Government and industry are used to dealing with, we can at least communicate with them in a language that they understand. It is no longer just a chalkstream but an ‘ecosystem service’ chalkstream that delivers ‘x’ million pounds of value per annum. The problem with this approach, however, is that this is a measure of ‘value’ based purely on what the species, process or ecosystem has to offer us.

Wildlife and natural processes should have their own intrinsic value, something that exists beyond our rather narrow and selfish frames of human reference. The Buff-tailed Bumblebee should be considered as having ‘value’ simply because it exists and not just because it pollinates our crops. The value that we put on a single bee should be the same as that which we put on a Hedgehog, a Barn Owl or, for that matter, a human being.

The fundamental problem that I have with ecosystem services is that the approach is about what other creatures and natural processes do for us; it is not about our responsibilities towards our fellow creatures. We should judge the consequences of our actions by the impact that they have on the environment within which we live and the creatures with which we share it. While an ecosystem services approach may appear to go some way to doing this, it rather misses the point by incorrectly presenting value purely in monetary terms.

Watch out for Hedgehogs

Over the next few weeks we will start to see Hedgehogs emerge from their annual winter hibernation. Providing individuals managed to find a suitable site in which to hibernate, the cold weather of recent weeks might actually have proved beneficial, with individuals not tempted to emerge early because of unseasonable warmth. Hedgehogs which do emerge too early waste valuable energy reserves and may be unable to complete a successful hibernation should temperatures fall again.

The Hedgehog is one of our most familiar mammals and should be quite unmistakeable; after all, it is our only mammal with a spiny coat! As such, you would think that we should have a pretty good understanding of how it is doing within the county and, indeed, how it is faring elsewhere across Britain. However, our knowledge is far from complete and all that we can really say is that the population is, at best, stable or, more likely, in a gradual long term decline. One particular habitat within which there seems to be strong anecdotal evidence of a decline is gardens. The change here may be linked with the increased use of garden chemicals, some of which may harm Hedgehogs directly or reduce populations of their favoured prey.

Another reason why our knowledge of Hedgehog populations may be less than expected is because of their largely nocturnal habits. While most Hedgehog behaviour takes place at night, they may sometimes be seen at dawn or dusk, or even during daylight if food is in short supply. However, hedgehog droppings are fairly distinctive and this means that the presence of a Hedgehog within a garden can often be determined through a casual search for droppings, ideally on an area of lawn. Activity is most pronounced during May and early June when, on warm nights in particular, you may hear the loud rhythmic ‘snorting’ calls of courting Hedgehogs from your garden. Courtship is a rather ill-tempered affair, the female rebuffing the amorous approaches of a male. The noise may not only wake you from sleep but can also attract other male Hedgehogs who happen to be in the vicinity. This halts the courtship, the male having to see off his rival before returning to the object of his affections (who may have done a bunk).

A new survey is being carried out this spring in order to gain a better understanding of the distribution of the Hedgehog within Norfolk. The survey is being conducted by the Norfolk and Norwich Naturalists’ Society and a simple recording form can be requested from the County Mammal Recorder, Dr Dave Leech. Send a self-addressed envelope with a first class stamp to Dr Dave Leech, c/o BTO, The Nunnery, Thetford, Norfolk, IP24 2PU.

Late arrivals face a tough time

Judging by the number of young Hedgehogs seen over the last couple of weeks, it seems likely that they bred somewhere in the grounds at work. Arriving back at the office late after an evening lecture, I have been greeted by several of these delightful little creatures, each helping to control the slugs and snails at large in the new wildlife-friendly garden. However, the sight or one of more of these youngsters out and about in daylight is less welcome. Normally nocturnal, Hedgehogs are only seen abroad during daylight hours when food is in short supply. As such, it seems that these youngsters will face an uphill struggle to put on the fat reserves that they need to get through the coming winter.

Hedgehogs show two main peaks in the birth of their young. Most are born in June but those from late litters can be born as late as August or even September. Given that the young do not gain their independence until they are some four to six weeks of age, it seems that these youngsters are from a late litter. Born blind in a breeding nest, they would have developed a set of white spines soon after birth; their eyes would have opened at roughly two weeks of age and by this stage they would already be capable of rolling into a ball as a defence against would-be predators. While the young from early litters should have little difficulty in reaching adult size prior to hibernation in late October or November, late-emerging youngsters may remain active through into December.

Fattening up in readiness for hibernation involves the deposition of white fat just under the skin and around the viscera. In addition, brown fat is also deposited and this plays an important role in starting the body up again when the time comes to emerge from hibernation. The magic weight for a Hedgehog is roughly 450g because individuals that fail to attain this weight before entering hibernation rarely survive the winter. The majority of young from the late litters end up entering hibernation at subadult size and so are unlikely to survive. Given the visual appeal of these mammals, and with a worrying decline in their population, it is easy to see why many of these underweight individuals are helped through the provision of some meaty pet food or taken to Hedgehog rescue centres as winter approaches. Foraging Hedgehogs can range over a sizeable area so I would not be surprised if some of those around here are getting a helping hand from some of the nearby households. I shall have to see how they fair over the next few weeks.

Bedding down for the winter

The mild November weather had its effect on our wildlife, with very late sightings of certain butterfly species and reports of hedgehogs still on the go. Most hedgehogs build their winter nests during October and are safely tucked-up by mid-November. However, winter hibernation remains a flexible option for our hedgehogs and many will continue to remain active if conditions (both in terms of temperature and food availability) are suitable. It is a common misconception that hibernation is an extended form of sleep, during which the body is rested. Instead, it is a complex behaviour used to conserve energy during periods when the animal may be faced with highly unfavourable conditions.

Since keeping warm is an energetically expensive strategy during winter, the hibernating hedgehog abandons this, allowing its body temperature to fall. This controlled reduction in body temperature, typically brings the animal’s temperature down to within a couple of degrees of the ambient temperature. If the ambient temperature falls to dangerously low levels, which would cause the hedgehog to literally freeze to death, then the hibernating hedgehog will burn off more of its body fat to generate the heat needed to keep the body temperature at a safe level.  This controlled reduction in body temperature results in a fall in oxygen consumption, heart rate and breathing rate, together with a restriction in the amount of blood flowing to the major organs. While an active hedgehog may have a heart rate of 250 beats per minute (bpm) this falls to just 5bpm during hibernation. Research has shown that hedgehog hibernation is most efficient at 4ºC and one of the features that helps the hedgehog operate at around this temperature is the winter nest itself. Made predominantly from leaves, pushed up against a larger object, the nest provides protection from the worst of the winter weather. Temperatures within the nest typically remain between 1 and 5ºC, ideal for hibernation.

Hibernation is not continuous and a hedgehog will “wake-up” every 7-10 days. This takes between three and four hours and the hedgehog will normally remain within the nest for a short period before re-entering hibernation. Very occasionally, individuals will venture outside, perhaps to establish a new winter nest. These periods of arousal are energetically demanding, collectively accounting for 80% of the energy expended during the entire hibernation period. As such, they must be important for the hedgehog. Fat reserves fuel hibernation and these are laid down prior to hibernation and need to be sufficient to last the winter. Any young or undersized hedgehog weighing less than about 1lb (450g) is unlikely to survive more than the briefest period of winter weather, so should be rescued to a hedgehog rehabilitation centre.