| dc.description | I studied the distribution, spatial organization and movements of groups of female and immature sperm whales (Physeter macrocephalus) in relation to chlorophyll concentration, amount of subsurface biomass, temperature gradients and underwater topography in the South Pacific. I examined the influence of these factors over a wide range of spatial scales (10 km-1800 km) using a range of temporal resolutions (a few hours to 130 years), and assessed the importance of food resources in determining sperm whale distribution. Data were collected during a year-long survey around the South Pacific, and extracted from 19$\rm\sp{th}$ century whaling logbooks and from satellite color observations. Principal component analyses and correlation analyses were used to assess the relationship between environmental measures and to relate them to sperm whale density. Groups were usually clustered over areas 10 to 70 km across, forming what I called "super-aggregations". The spatial scale of these super-aggregations seems to reflect closely the spatial scale of prey patches (infered by indirect evidences). These super-aggregation were clumped in "concentrations" (about 550 km across), characterized by high sub-surface biomass and high underwater relief. When the data were averaged over a large temporal scale (8-130 years), sperm whales were generally found in upwelling and high chlorophyll concentration zones over spatial scales of 200 to 1800 km. An investigation of defecation rates suggested that movement patterns of groups of sperm whales were related to feeding success: groups with low feeding success tended to travel in straight lines, while groups with high feeding success tended to zigzag over areas roughly 40-60 km across. I conclude that the distribution, spatial organization and movements of groups of sperm whales are closely related to the distribution of food resources over spatial scales of a few tens of km to a few thousand km. | en_US |
