Despite global declines in the abundance of marine predators, knowledge of foraging ecology, necessary to predict the ecological consequences of large changes in marine predator abundance, remains enigmatic for many species. Given populations suffering severe declines are of conservation concern, we examined the foraging ecology of southern sea lions (SSL) (Otaria flavescens) - one of the least studied otariid (fur seal and sea lions) that have declined by over 90 % at the Falkland Islands since the 1930s. Using a combination of animal-borne tracking devices and stable isotope analysis of vibrissae, we redress major gaps in the knowledge of SSL ecology and quantify patterns of individual specialization. Specifically, we revealed two discrete foraging strategies, these being inshore (coastal) and offshore (outer Patagonian Shelf). The majority of adult female SSL (72 % or n = 21 of 29 SSL) foraged offshore. Adult female SSL that foraged offshore travelled further (92 ± 20 km vs. 29 ± 4 km) and dived deeper (75 ± 23 m vs. 21 ± 8 m) when compared to those that foraged inshore. Stable isotope analysis revealed long term fidelity (years) to these discrete foraging habitats. In addition, we found further specialization within the offshore group, with adult female SSL separated into two clusters on the basis of benthic or mixed (benthic and pelagic) dive behaviour (benthic dive proportion was 76 ± 9 % vs. 51 ± 8 %, respectively). We suggest that foraging specialization in depleted populations such as SSL breeding at the Falkland Islands, are influenced by foraging site fidelity, and could be independent of intra- specific competition. Finally, the behavioural differences we describe are crucial to understanding population-level dynamics, impediments to population recovery, and threats to population persistence.