Traditional methods for studying cetacean prey include net capture, optical methods, or stomach content analysis. Yet deep-sea cephalopods, in particular, are understudied, and many have never been observed alive in their habitats or captured as adults (Hoving et al., 2014). For instance, it is estimated that sperm whales alone annually feed on as many cephalopods in terms of biomass as human fisheries catch worldwide. Thus, we expect that deep-diving cetaceans selectively target distinct foraging zones that hold specific prey communities to optimize their foraging performance.Ĭephalopods are extremely abundant and play a pivotal role in marine food webs as both predators and prey (Hoving et al., 2014). Because their dives to remote depths are energy consuming, the prey reward needs to be substantial to make the dives profitable. The use of on-animal recorders has revealed that multiple species of cetaceans make extensive use of the deep sea, specifically the meso- (200–1,000 m depth) and bathypelagic (1,000–4,000 m depth) zones, to hunt for diverse, often cephalopod-dominated prey populations (Tyack et al., 2006). Such changes can include interactions between elusive and sometimes giant deep-sea predators such as cetaceans and their prey. Many of these changes occur outside of the range of human observation and are unrecognized so that effective conservation is limited. Climate change and industrial exploitation are exerting increasing pressure on deep-sea ecosystems, causing a decline in global ecosystem health and ecosystem services.

In this vast environment, animals are hard to find, and interactions among them are even harder to investigate (Robison, 2009). At depths below 200 m, the pelagic deep sea comprises the largest, but least explored, part of the ocean.

Predator vs prey marine