DIURNAL ACTIVITY IN THE SAMOAN FLYING FOX, PTEROPUS-SAMOENSIS

Speakman and co-workers suggested the diurnal Samoan flying fox, Ptero pus samoensis, may be at risk of hyperthermia when flying during the d ay, particularly at high levels of insolation. We monitored activity o f this bat and climate simultaneously at two different sites and four times of year in American Samoa. Flight activity varied significantly with time of day, between days, study sites and seasons. Out of the si x data sets collected, the four with the highest mean levels of insola tion showed a significant decrease in bat numbers with increasing temp erature and sunlight. When each individual activity count was directly compared to the predict-ions of Speakman and co-workers' biophysical model, 85-95% of bat flight activity was found to be in conditions the model suggested would not pose a risk of hyperthermia. This supports the suggestion that in extreme conditions the animals would not fly as they risked overheating. The 5-15% of counts in which animals were se en to fly in conditions the model predicted they should not may be exp lained by erroneous assumptions underlying the model predictions.