It’s the wettest of all African deserts, the great Kalahari.

The sands of the Kalahari cover more of southern Africa than any other desert. But the higher rainfall here gives it a very distinctive appearance. More like a savanna, its sandy ridges carpeted with grasses and a scattering of trees. In the wet season, the Kalahari sands are loosened by the rain, making them easier to excavate.

Damara mole-rats who spend their lives underground are now at their most active, hunting for roots and bulbs. But digging takes one thousand times more energy than traveling on the surface. And even in this greenist African deserts, the bulbs can be widely spread.

Living on its own, a single mole rat would never find enough to eat. So these small rodents have evolved a cooperative life style with up to forty family members working together. Like ants or bees, only the queen mole rat breeds and all her workers are sterile females. But everybody will benefit from the extra mouths who eventually join in the hunt for food.

Damara mole rats are unusual in that their lips are actually behind their front teeth. It helps them to avoid swallowing sand while digging. But it also stops them drinking. So they must extract all the moisture they need from the bulbs.

During the wet season, the bulbs are gathered quickly before they germinate and lose their goodness. The mole rats store them in special larders as insurance against the dry months ahead.

words:
1.ridge:any long raised strip脊

2.scattering:stretch长长的分散的带

3.excavate:to dig挖掘

4.extract:disinter...out of from...挖出

5.germinate:to sprout from a seed发芽