The energy assimilation efficiency of emperor penguins, Aptenodytes forsteri, fed a diet of Antarctic krill, Euphausia superba.

Captive emperor penguins in Antarctica hand-fed Antarctic krill assimilated an average of 70.5% +/- 1.7% (n = 3) of the energy in the diet. Water intake estimated by tritiated water turnover was 9.4% +/- 2.4% less than that measured gravimetrically. Tritium took 1.5 h from injection to equilibrate with the penguins' body water pools.