Fig. 1.

Baikal seals hunt endemic amphipods in Lake Baikal. (A) M. branickii, the world’s only freshwater amphipod with a fully pelagic lifestyle (Photo credit: S. Didorenko). (B) Image from animal-borne video footage, showing the seal about to hunt a M. branickii (yellow arrow) by stretching its neck. M. branickii is in an upside-down position with its paired antennae visible. (C) A foraging dive on M. branickii by a seal, showing depth, swim speed, pitch angle (with positive and negative values indicating upward and downward attitude, respectively), and body acceleration (i.e., the vectorial sum of triaxial accelerations). The simultaneously recorded video footage showed that the seal encountered and hunted M. branickii nearly continuously (total, 154 individuals) during the bottom phase (denoted by many red markers that appear as a line).