Pinniped High levels of organic chemicals accumulate in these animals since they are near the top of food chains and have large reserves of blubber. Lactating mothers can pass the toxins on to their young. These pollutants can cause gastrointestinal cancers, decreased reproductivity and greater vulnerability to infectious diseases. Other man-made threats include habitat destruction by oil and gas exploitation, encroachment by boats, and underwater noise. Pinniped Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic marine mammals. They comprise the extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared
Pinniped into two monophyletic subfamilies: Monachinae, which consists of "Mirounga", Monachini and Lobodontini; and Phocinae, which includes "Pusa", "Phoca", "Halichoerus", "Histriophoca", "Pagophilus", "Erignathus" and "Cystophora". In a 2012 review of pinniped taxonomy, Berta and Morgan Churchill suggested that, based on morphological and genetic criteria, there are 33 extant species and 29 subspecies of pinnipeds, although five of the latter lack sufficient support to be conclusively considered subspecies. They recommend that the genus "Arctocephalus" be limited to "Arctocephalus pusillus", and they resurrected the name "Arctophoca" for several species and subspecies formerly placed in "Arctocephalus". More than 50 fossil species have been described.