Marine mammals are classified into four different groups: cetaceans (whales, dolphins, and porpoises), pinnipeds (seals, sea lions, and walruses), sirenians (manatees and dugongs), and marine fissipeds (polar bears and sea otters).
There are over 70 different species of cetaceans that spend their whole lives in water. Cetaceans are categorized into two main groups: baleen whales (mysticetes) and toothed whales (odontocetes). Pinnipeds are carnivores that use flippers for movement on land and in the water. Their name comes from the suborder called pinnipedia which means "fin-footed." Pinnipeds spend the majority of their lives swimming and eating in water and come onto land or ice floes to bear their young, sunbathe, and molt. Like cetaceans, sirenians also spend their whole lives in water. "Sirenia" comes from the word "siren." "Sirens" are legendary Greek sea beauties who lured sailors into the sea. We think historic mermaid sightings were actually sirenians, not the mythical half women, half fish. The marine fissipedsoffsite link are unique because they are considered marine mammals, but spend most of their time on land and only part of the time in the water, mainly to hunt for their food.
They also represent a variety of ecological roles, including herbivores (manatees), filter feeders (baleen whales), and top predators (killer whales); but what is a marine mammal? Marine mammals meet the five characteristics of a mammal. They breathe air through lungs, are warm-blooded, have hair (at some time during life), bear live young, and produce milk to nurse their young. They are a diverse group of mammals with unique physical adaptations allowing them to thrive in the marine environment with extreme temperatures, depths, pressure, and darkness.
Threats and protection
Threats to marine mammals are largely from human impacts, including accidental capture in fishing gear, habitat destruction, poaching, pollution, harassment, and ship strikes. All marine mammals in waters of the United States are protected under the Marine Mammal Protection Act (MMPA), which includes over 60 marine mammal species. NOAA's National Marine Fisheries Service works in collaboration with several partners to protect these species. Citizens can also help protect marine mammals by showing proper ocean etiquette. Admire them from a distance and never touch, feed, harm, or swim with a marine mammal.
The education resources in this collection provide educators and students opportunities to explore the adaptations, population dynamics, ecology, threats, behaviors, and anatomy of marine mammals. This collection includes several videos, lessons, activities, games, data resources, and career profiles to help students better understand the biology of marine mammals as well as their role in protecting these species.