Identify the species in which the natural selection should favor the highest proportion of juxtamedullary nephrons.

Juxta medullary nephrons have long loops of Henle. These nephrons help in production of concentrated urine. Concentrated urine helps in water conservation. Prevention of water loss is a very important xeric adaptation. Such an adaptation is vital for desert animals like kangaroo rat and hence natural selection should favor the high proportion of juxtamedullary nephrons in them.