Penguin seal carbon dating
Only three phocid species—all of the monk seals—are tropical and they are all either highly endangered or, in two cases, extinct.The fur seals are also found in the tropics, but their absolute abundance is low.In particular, elephant seals exhibit tremendous stamina while diving for their food.Each elephant seal dive averages about 30 minutes in length, with only a couple of minutes between dives, and they have been seen maintaining that schedule for months on end.It takes between three and six years for pups to reach sexual maturity; females produce only one pup a year, and only about 75 percent survive.Female seals and sea lions live between 20 and 40 years.The ones that eat mostly fish specialize in oil-bearing species like eels, herrings, and anchovies because they swim in shoals and are easy to catch, and are good energy sources.Seals can dive deeply and for extended periods (up to 2 hours for some species) because they have a higher concentration of hemoglobin in their blood and their large amounts of myoglobin in their muscles (both hemoglobin and myoglobin are oxygen-carrying compounds).
Like cetaceans, they conserve oxygen when diving by restricting blood flow to only vital organs and slowing their heart rates by about 50 percent to 80 percent.
Seals and sea lions are highly evolved for swimming, including flippers, a streamlined fusiform (tapered at both ends) shape, thick insulation in the form of fur and/or subcutaneous layer of blubber, and increased visual acuity for foraging at extremely low light levels.
Seals and sea lions are in the order Carnivora and suborder Pinnipedia, along with walruses.
Seals and fur seals are related to bears, descended from an otter-like terrestrial ancestor, and they all have a more or less aquatic lifestyle.
The pinnipeds include 34 species and 48 subspecies.The most famous is a captive male harbor seal at the New England Aquarium named "Hoover" (1971–1985). In polar environments, seals restrict blood flow to their skin surface to keep from releasing internal body heat to the ice and freezing water. Blood is sent toward the extremities, allowing heat to release into the environment and letting the seal cool its internal temperature.