The only relevant time is the conditions during that time period. I use the term desert to indicate lack of water for flies to breed. During such a time I would not be surprised to discover that flies don't wander as far and are less likely to find a corpse. I would not be surprised if the animals are what brings the fly's in such circumstances.
Semi-arid (least dry), arid (dry), and hyper-arid (driest)
I believe the Dehesa area would be considered desert.