Thursday, 18 September 2008

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.

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