Of 24 wet season stands, all but 1 were accurately classified, that stand being classified as transitional. Samples of the youngest fully expanded leaf blades collected from 3-6 individuals of the dominant grass species at each location were processed and anaylsed as described previously 11 . The level of N was determined by gas chromatography on a Carlo Erba 1500 N-analyser and all other elements were determined on a Leeman Labs PlasmaSpec 2.5 Inductively Coupled Argon Plasma Spectrometer in simultaneous mode. Nevertheless, ungulate requirements are broadly similar 14 and nutritional deficiencies leading to veterinary symptoms have been extensively documented in wild African ungulates 3 . Apart from Na, which is supplemented everywhere, P-deficiency is the most prevalent livestock deficiency throughout the world 12 .
Seasonal ranges are flexible and defined by average annual usage.
In the wet season, migrants move to transitional areas during periods of rainfall failure and even to dry-season areas during extended periods of rainfall failure elsewhere 6 . Neither do all animals in a herd move together. This divergent movement is probably related to growth and lactation demands, and forage levels of Cu. Minerals that are at elevated levels in grasses of wet-season and transitional ranges are required at substantially higher concentrations by females at late stages of pregnancy and in lactation and by growing young 12 . These birth peaks result in the greatest lactation demand when there is a high probability of sufficient rainfall to support the migratory herds on the SE Serengeti Plains 13 .