BODY TEMPERATURES OF FREE-LIVING AFRICAN PENGUINS (SPHENISCUS-DEMERSUS) AND BANK CORMORANTS (PHALACROCORAX-NEGLECTUS)

Two free-living seabirds (the African penguin Spheniscus demersus and the bank cormorant Phalacrocorax neglectus) were equipped with stomach temperature-loggers to study body temperature changes during foraging , Body temperature in these endotherms was environmentally and activit y-dependent and varied in the case of the cormorant by over 5 degrees C, Considerations of heat flux show that such flexibility confers cons iderable energetic advantages: by allowing body temperature to drop wh en the heat loss to the environment is high, such as in water, birds m ay save the energy that would normally be necessary to compensate for this drop, It appears that, in cormorants, low body temperature result ing from extended time in water can subsequently be elevated using sol ar energy when the birds return to land in a manner similar to that of ectotherms. In the better-insulated penguins, muscle-generated heat d uring swimming is used to re-elevate low body temperature, Continued s wimming eventually causes body temperature to rise above normal restin g levels so that metabolic rate could theoretically be dramatically re duced immediately post-exercise when the temperature drops to some cri tical level before any increase in metabolism is necessary to correct it.