African and European hedgehogs originated from the same root stock, yet each has developed its own unique and different characteristics. It is apparent that from the beginning, hedgehogs have had the ability to enter a stuporous state whenever conditions become unfavorable to their ability to maintain body temperature or locate insects, their primary food source.
As the species migrated away from one another, each entered into different habitats. The European hedgehog adapted itself to a habitat wherein cold winter weather is the norm for long periods each year. The ability to enter a stuporous state was modified into the ability to hibernate, that is, the ability to drastically reduce the animal's metabolic rate as a result of cold and reduced sunlight. It's main food source being gone and the cold temperatures inhibiting it's ability to maintain body heat, the European hedgehog cannot survive unless it hibernates. Without this ability it would never survive such a climate.
The African species, on the other hand, had to adapt to an entirely dissimilar habitat. Instead of the freezing winters of Europe, the African hedgehog had the blazing summers of the African grasslands to contend with. Once again, food source and body heat were the two motivating factors, but the resulting response was remarkably different.
During the hot summer months (which, coincidentally coincide with our winters) just following the rainy season, the African plains become very hot and dry. The hedgehog's food source dwindles and its ability maintain body temperature is compromised. The heat of the day is just too great for an animal such as this.
In response, the hedgehog seeks out a cool hiding place and, like the European hedgehog, enters a semi-stuporous state. This normally occurs between the months of January to March. Unlike the European hedgehog, however, this is not hibernation. Rather, it is more fittingly described using the term "Aestivation" - a period of heat-induced stupor that is less intense than hibernation. The animal's metabolic rate slows, but not nearly to the same low levels that occur during hibernation. The African hedgehogs still venture out from their hiding places on a fairly regular basis, but their activity levels are greatly reduced and they may even sleep for periods of up to one week at a time.
Although the two conditions - Hibernation and Aestivation - appear similar at first and are both based upon the same environmental response of the original foundation stock hedgehog, the long-term isolation and dissimilar climatic conditions of the European and African species has made them very different from one another.
European hedgehogs have adapted to a climate wherein they are regularly exposed to extremes of both hot and cold and can, therefore, both hibernate and aestivate. African hedgehogs, on the other hand, are rarely if ever exposed to extreme cold. They have adapted to a hot climate only and as a result, have only a vestigial ability to hibernate remaining.
When exposed to cold, their bodies respond by slowing the metabolic rate, but because of their keen adaptation towards aestivation, that response is not nearly great enough to be successful. Their metabolism does not slow enough for full hibernation and as a result most African hedgehogs who are forced to hibernate do not recover if they are not revived after the first 72 hours. They die of hypothermia, starvation, or both.