Chapter 12 Marine Birds And Mammals In Polar Seas Copyright © 2004 Jones and Bartlett Publishers The polar ends of Earth experience long winter nights without sunlight, sea surface temperatures around 0°C, perpetual coverage by permanent fast ice, and additional ice coverage due to the seasonal freezing and thawing of pack ice.

Marine Birds And Mammals In Polar Seas Strong contrasts exist between the north and south poles. The Arctic is an ice-covered ocean surrounded by continents. The Antarctic is a frozen continent surrounded by ice-covered seas. Chapter 12

Marine Birds And Mammals In Polar Seas Fig Approximate distribution of fast ice (summer) and pack ice (winter) in the the north and south polar regions (SeaWiFS). Chapter 12

The Arctic Phytoplankton productivity patterns at higher latitudes are marked by large swings between long winters of essentially no productivity and short bursts of high summertime production. Phytoplankton productivity patterns at higher latitudes are marked by large swings between long winters of essentially no productivity and short bursts of high summertime production. These in turn feed relatively large consumers and lead to short food chains supporting large aggregations of marine mammals and seabirds. These in turn feed relatively large consumers and lead to short food chains supporting large aggregations of marine mammals and seabirds. Chapter 12

The Arctic Marine mammals and seabirds that cope with the seasonal variability in their food supplies via extended fasting and long migratory excursions to lower-latitude waters in winter. Marine mammals and seabirds that cope with the seasonal variability in their food supplies via extended fasting and long migratory excursions to lower-latitude waters in winter. Chapter 12 Fig Generalized migratory patterns of large whales between summer feeding and winter breeding grounds. Adapted from Mackintosh 1966.

The Arctic Arctic Mammals Arctic Mammals –The growth rates of young marine mammals can be truly astounding. These prodigious growth rates are supported by an abundant supply of high-fat milk. Chapter 12 Fig Harp seal pup on Canadian pack ice (Ablestock).

The Arctic Arctic Mammals Arctic Mammals –Several species of seals, including ringed, harp, and hooded, breed on arctic fast or pack ice. –These species all show a reduced level or complete absence of polygyny. –Mating in the water is common. Chapter 12

The Arctic Arctic Mammals Arctic Mammals –Polar bears have few specialized adaptations for efficient swimming and usually prey on ice seals. –They endure prolonged seasonal fasts as the availability of food declines or when reproductive activities prevent foraging. Chapter 12 Fig a A polar bear mother and her twin cubs at rest (Courtesy of NOAA).

The Arctic Arctic Mammals Arctic Mammals –Mysticete whales, among the largest animals on Earth, are filter feeders of crustaceans or small shoaling fishes. –All mysticetes show reverse sexual dimorphism, which may provide females with larger lipid stores to help offset the energetic costs associated with rapid fetal growth and lactation. Chapter 12

The Arctic Arctic Mammals Arctic Mammals –Mysticete whales exploit these polar and subpolar production systems with intensive summer feeding followed by long-distance migrations to low latitudes in winter months, with both mating and calving occurring in warm and often protected waters. Chapter 12

The Arctic Arctic Mammals Arctic Mammals Chapter 12 Fig Pattern of latitudinal migrations of female gray whales through a complete two-year reproductive cycle. (Adapted from Sumich, 1986.)

The Arctic Arctic Mammals Arctic Mammals Arctic waters are inhabited, or at least visited, by belugas, narwhals, and killer whales. Arctic waters are inhabited, or at least visited, by belugas, narwhals, and killer whales. Belugas are medium-sized whales with a very flexible neck, small flippers, thick blubber, and a stout dorsal ridge used to break through ice from below. They feed on seasonally and locally abundant fishes and invertebrates, both in the water column and on the seafloor. Belugas are medium-sized whales with a very flexible neck, small flippers, thick blubber, and a stout dorsal ridge used to break through ice from below. They feed on seasonally and locally abundant fishes and invertebrates, both in the water column and on the seafloor. Chapter 12 Fig a An arctic toothed whale, beluga, Delphinapterus leucas

The Arctic Arctic Mammals Arctic Mammals –All narwhals possess a tusk that is actually an elongated upper tooth projecting through the lip. –They feed mostly on polar and arctic cod, and sometimes dive to depths greater than 1000 m to feed on bottom fishes and midwater squid. Chapter 12

The Arctic Arctic Mammals Arctic Mammals –Killer whales, the most easily recognized of all the whales, are found from tropical waters to both poles. Chapter 12 A killer whale, Orcinus orca, surfacing amidst arctic ice (Courtesy of NOAA).

The Arctic Arctic Mammals Arctic Mammals Chapter 12 Fig Transient killer whale attacking a Dall’s porpoise in Alaskan costal waters (Courtesy R. Baird).

The Arctic Arctic Birds Arctic Birds –Seabirds obtain their food from the sea, excreting excess salt ingested during feeding with nasal salt glands. –All species of seabirds are either Charadriiformes (gulls, skuas, jaegers, terns, auks, and puffins), Procellariiformes (petrels, fulmars, and albatrosses), or Sphenisciformes (penguins). Chapter 12

The Arctic Arctic Birds Arctic Birds –Only northern fulmars, ivory gulls, and Ross’s gulls consistently depend on arctic ice-associated prey in summer. Chapter 12 Fig A northern fulmar, Fulmarus glacialis, in search of prey.

The Antarctic All antarctic communities depend directly or indirectly on Euphausia superba, a 6-cm-long, 1-g, herbivorous crustacean that occurs in enormous swarms around much of the Antarctic continent. All antarctic communities depend directly or indirectly on Euphausia superba, a 6-cm-long, 1-g, herbivorous crustacean that occurs in enormous swarms around much of the Antarctic continent. These vast shoals of krill probably support half the world’s biomass of seals, and a large proportion of its baleen whales and seabirds as well. These vast shoals of krill probably support half the world’s biomass of seals, and a large proportion of its baleen whales and seabirds as well. Chapter 12

The Antarctic Chapter 12 Fig Antarctic food web with krill, Euphausia superba, occupying a central position on the second trophic level.

The Antarctic Antarctic Birds Antarctic Birds –Most polar seabirds are found in the southern hemisphere, nesting at high latitudes during summer, often in enormous and crowded colonies, and then leaving to spend winter months at lower latitudes elsewhere. Chapter 12

The Antarctic Antarctic Birds Antarctic Birds –Adelie and emperor penguins are abundant in antarctic pack-ice habitats. Chapter 12 Emperor penguins (Courtesy of NOAA)

The Antarctic Antarctic Mammals Antarctic Mammals –Crabeater seals, the most abundant seal on Earth, forage almost exclusively on E. superba, using their highly modified teeth as effective strainers. –These monogamous seals spend the entire year on pack ice. Chapter 12

The Antarctic Antarctic Mammals Antarctic Mammals –Weddell seals are found associated with openings in the fast ice that they maintain as breathing holes by constant abrasion with their teeth. They dive to 600 m for 80 minutes or more to feed on antarctic cod and other large bottom fish and squid. Chapter 12 Fig Several Weddell seals on fast ice around a permanent lead or opening.

The Antarctic Antarctic Mammals Antarctic Mammals –Filter-feeding blue, fin, humpback, and minke whales occupy antarctic waters to feed on krill in summer. Chapter 12 Fig Final phase of humpback whale bubble-net feeding. Circular trace of the bubble net is still visible.

The Antarctic Antarctic Mammals Antarctic Mammals –Today, blue, fin, and humpback whale populations still remain depleted as a result of the intense commercial whaling during the first half of the 20th century. –With the larger whale species removed from antarctic food webs, numbers of smaller minke whales, Adelie penguins, crabeater and leopard seals, and fishes that also rely on E. superba have increased dramatically. Chapter 12