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We trailed these young sisters as they wound their way around the muddy lake. From a distance the pair looked healthful, as one would expect since the crater is considered a lion paradise. Food and water are plentiful and the steep crater walls and limited ingress paths make it easy for lions to defend their territory.
As we drew closer, we noticed the lions seemed distraught and were coated with flies. As I was taking these pictures, I was thinking "I don't know why she's covered in flies. I hope she doesn't die." Since returning to Canada, I've read that there was an explosion in the population of bloodsucking "stomoxys" flies in Ngorongoro. While many animals suffer from painful sores caused by fly bites, lions are most affected.
On March 16, 2001 the BBC reported that at least six lions (out of a population of 68) had already died due to constant fly bites. According to the BBC, the cats are so traumatized they don't eat and spend all their time trying to get away from the flies. Perhaps the lions we saw were seeking relief rolling in the mud.
The stomoxys population increases rapidly when there is an extreme climate change. After a long drought in Ngorongoro, it has been raining heavily recently. There was a similar outbreak in 1962 when the population of at least seventy lions was reduced to about ten.
The crater layout that makes it easy for the lions to patrol the perimeter deters what the population needs most: the entry of outside lions with new genes. As the crater and its lions have been naturally isolated for millennia, the lion population is highly inbred. According to Henry Fosbrooke, former Ngorongoro conservator, the tribulations of the crater lions may foretell the fate of other animals. Increased human population and cultivation around reserves creates virtually impermeable boundaries. Many species have recently become isolated in small populations. Inbred populations tend to have little variability among their immune systems and are therefore more susceptible to outbreaks.