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
Mammal destruction]], though there are efforts to combat this. [[File:Mammal species pie chart.svg|thumb|upright=1.35|The orders [[Rodent]]ia (blue), [[Chiroptera]] (red) and [[Soricomorpha]] (yellow) together make up over 70% of mammal species. Mammal classification has been through several iterations since [[Carl Linnaeus]] initially defined the class. No classification system is universally accepted; McKenna & Bell (1997) and Wilson & Reader (2005) provide useful recent compendiums. [[George Gaylord Simpson]]'s "Principles of Classification and a Classification of Mammals" (AMNH "Bulletin" v. 85, 1945) provides [[systematics]] of mammal origins and relationships that were universally taught until the end of the 20th century. Since Simpson's classification, the [[fossil