Scale-dependent correlation of sperm whale distribution with environmental features and productivity in the South Pacific

The purpose of this study was to investigate sperm whale Physeter macrocephalus distribution in relation to underwater topography, temperature gradients and primary and secondary productivity. The influence of these fathers over different spatial scales (80 to 640 nautical miles) was examined, and the importance of food resources in determining sperm whale distribution was assessed. The data were collected during a survey around the South Pacific Principal component analyses were used to assess the relationship between the environmental measures recorded and to relate them to sperm whale density. The first principal component was considered as an index of secondary productivity, the second as an index of underwater topography, and the third as a contrast between deep and surface productivity. Sperm whale density was correlated with the first and the second principal components over spatial scales equal to or greater than 320 n miles. This result indicates that sperm whales are generally distributed within large areas which are characterized by high secondary productivity anti steep underwater topography. The size of these areas may reflect the distances over which the groups of whales move in search of food The absenced of correlation over smaller spatial scales suggests that factors other than the distribution of food resources also influence sperm whale distribution over these scales.