abundance acoustic monitoring baiji behaviour bioaccumulation bioacoustics bottlenose dolphin bycatch captivity capture classification coloration comparison conservation construction cortisol disease distribution divergence diving dolphin echolocation economics entanglement evolution feeding fossil genetics growth habitat use hearing history hormones immunology killer whale leucism life history metabolism morphology mortality neurology noise parasites phylogeny physiology pollutants population structure population trends predation rehabilitation release reproduction reserve skeleton speciation stranding stress tagging vision whale