Cannibalism is certainly not unheard of in auchenipterids, and I wouldn't be surprised if it did indeed happen; I do not recall any particular instance of gulpers of vastly different sizes ever being successfully cohabitated, though I could be wrong. Neither gulper in the video seems to be in the best of health (the smaller one seems quite ill), which may have some impact.This is the first time I hear of gulper eating a gulper. Do you believe the poster or not?