Deep-sea predator niche segregation revealed by combined cetacean biologging and eDNA analysis of cephalopod prey

Fundamental insight on predator-prey dynamics in the deep sea is hampered by a lack of combined data on hunting behavior and prey spectra. Deep-sea niche segregation may evolve when predators target specific prey communities, but this hypothesis remains untested. We combined environmental DNA (eDNA) metabarcoding with biologging to assess cephalopod community composition in the deep-sea foraging habitat of two top predator cetaceans. Risso's dolphin and Cuvier's beaked whale selectively targeted distinct epi/meso- and bathypelagic foraging zones, holding eDNA of 39 cephalopod taxa, including 22 known prey. Contrary to expectation, extensive taxonomic overlap in prey spectra between foraging zones indicated that predator niche segregation was not driven by prey community composition alone. Instead, intraspecific prey spectrum differences may drive differentiation for hunting fewer, more calorific, mature cephalopods in deeper waters. The novel combination of methods presented here holds great promise to disclose elusive deep-sea predator- prey systems, aiding in their protection.

Automated summary

Insights into predator-prey dynamics in the deep sea are hindered by a lack of comprehensive data on hunting behavior and prey spectra. Risso's dolphin and Cuvier's beaked whale selectively target different cephalopod communities in deep-sea foraging habitats, with predator niche segregation not solely driven by prey community composition but potentially by intraspecific differences in prey spectra and habitat selection. The novel combination of eDNA metabarcoding and biologging shows promise in revealing elusive deep-sea predator-prey systems and aiding in their conservation efforts.