Ultrahigh foraging rates of Baikal seals make tiny endemic amphipods profitable in Lake Baikal

Despite being ubiquitous in aquatic environments, amphipods are rarely targeted by seals or toothed whales, likely because they contain too little energy to warrant catching individually. We report a remarkable case of Baikal seals in Lake Baikal, among the least studied seal species. Seals individually hunted tiny (<0.1 g) endemic amphipods (the world's only freshwater planktonic species) at the highest rates ever recorded for aquatic mammals, primarily by following diel depth changes of amphipod swarms. Baikal seals have specialized comb-like cheek teeth, allowing them to expel water that enters the mouth during high-speed foraging. Thus, even tiny organisms can be important foods for aquatic mammals that catch prey individually, if the environment and predators' adaptations allow high foraging rates.