Southern hemisphere humpback whales (Megaptera novaeangliae) are capital breeders that use stored energy reserves to migrate annually from their high latitude feeding areas to their low latitude breeding areas. They are thought to follow the classical feeding paradigm of feeding exclusively on Antarctic krill (Euphausia superba) during the austral summer in the highly productive waters of the Southern Ocean. For the last two decades, observations and studies have put the validity of the classical feeding paradigm under scrutiny because diverse lines of evidence suggest more feeding heterogeneity occurs for southern hemisphere humpback whales than has been assumed under the classical feeding paradigm. This may be an indication that the paradigm has either always been an oversimplification, or that the feeding ecology of humpback whales is subject to more natural ecosystem variability than previously expected. Alternatively, it may be a sign of present-day changes in the feeding ecology of southern hemisphere humpback whales related to climate-induced variability in the Antarctic sea-ice ecosystem. Climate change induced alterations to the abiotic environment, such as warming ocean temperatures or declines in sea ice extent and duration, are thought to lead to biomass reduction of sympagic Antarctic krill. This in turn is hypothesised to carry ecosystem cascade effects impacting highfidelity Antarctic krill consumers like southern hemisphere humpback whales. Detailed long-term information of the past and current diet of humpback whales are needed to successfully differentiate between natural feeding heterogeneity of these populations and their feeding response to climate-induced environmental change. This thesis aims to evaluate the dietary niche width and trophic position of southern hemisphere humpback whales across a circumpolar spatial and long-term temporal scale.