Why are there no aquatic turtles in the relict waters of the Sahara?

Abstract

The evidence for the presence of relicts of aquatic turtles ( Mauremys leprosa and Pelomedusa subrufa ) in the African deserts is reviewed. It is concluded that, in contrast to the Nile crocodile, no relict populations of these species are extant today, except at the fringes of both the Sahara and the Namib. The latter are considered pioneers rather than relicts. A hypothesis is formulated to account for these facts. A combination of a lack of predictability of nonpermanent aquatic biotopes, intolerable predation levels on all stages of the life cycle, but especially on eggs and hatchlings, and competition with other carnivores in permanent waters, are suggested to have caused the extinction of turtle populations in African deserts when the aquatic biotopes shrank in size and diversity, at the end of the Holocene pluvial.