EXTERNAL DEVICES ON PENGUINS - HOW IMPORTANT IS SHAPE

Many researchers use external recording or transmitting devices to elu cidate the marine ecology of fish, mammals and birds. Deleterious effe cts of these instruments on the parameters researchers wish to measure are hardly ever discussed in the literature. Research has shown that, in penguins, volume and cross-sectional area of instruments negativel y correlate with swimming speed, dive depth and breeding success, and that device colour affects bird behaviour. Here, a large (200 g, cross -sectional area 2100 mm(2)) streamlined device was attached to the low er back of Adelie penguins (Pygoscelis adeliae on Ardley Island, South Shetland Islands in 1992) and its effects on bird swimming speed and energetics were measured in a water canal in Antarctica. Although the device was 10.5% of penguin cross-sectional area, swimming speed was r educed by only 8.3% and mean power input increased by only 5.6% while swimming. Although our streamlined device was five times more volumino us than one of our older units, the effect on swimming energetics coul d be reduced by 87%.