Fish 475: Marine Mammalogy 20 May 2009

Transcription

1 Fish 475: Marine Mammalogy 20 May 2009 Trophic biology II Anthony J. Orr SAFS/UW & NMFS/NOAA Course website:

2 1 Trophic biology of pinnipeds Otariids: Shallow divers 1) Specialists on organisms of the vertically-migrating deep scattering layer (DSL), particularly small fish and, cephalopods, or: 2) Coastal forage fish specialists

3 Trophic biology of pinnipeds 2 Otariids as central place foragers during breeding season NOAA

4 Trophic biology of pinnipeds 3 Otariids in the nonbreeding season: In some species (e.g., northern fur seals), ties to land are abandoned. In others (e.g., Steller sea lions), ties to haulouts and coastal habitats are maintained yearround. NOAA

5 Trophic biology of pinnipeds 4 Phocids: Variable in feeding anatomy and diving behavior - Most do not forage at all during lactation; - May or may not be central place foragers.

6 Trophic biology of pinnipeds 5 Phocid case studies: 1) Crabeater seal: Feed primarily on krill; Post-canine teeth modified as filters,

7 Trophic biology of pinnipeds 6 Phocid case studies: 2) Leopard seal: Feed on penguins & small fur seals...

8 Trophic biology of pinnipeds 7 Phocid case studies: 2) Leopard seal:.... and they also feed on krill! (check out the postcanine teeth)

9 Trophic biology of pinnipeds 8 Phocid case studies: 3) Northern elephant seals: Feed on DSL and abyssal fish and cephalopods; Make two extended excursions to the open sea each year

10 Trophic biology of pinnipeds 9 Phocid case studies: 4) Hawaiian monk seals Feed on coral reef fishes and crustaceans; Limited to tropical latitudes.

11 Trophic biology of pinnipeds 10 Phocid case studies: 5) Harbor seals: One of few phocids that forages while nursing a pup; Widespread in North Pacific and North Atlantic; Feed on a variety of coastal fishes, including herring, hake, salmon, surf perch, and rockfish

12 Walruses: Benthic feeding: Trophic biology of pinnipeds 11 G. Anderson Sedimentary habitats Shallow water (<100m) Invertebrate prey, primarily clams (up to 5000 ingested per feeding session); Utilize vibrissae to locate prey; G. Anderson Utilize water jets, fanning of sediment with flippers, and shoveling with muzzle to excavate prey; Utilize suction to extract prey tissue from shells G. Ehlme G. Ehlme

13 Trophic biology of pinnipeds 12 Walruses: Benthic feeding: Important influence on the structure and dynamics of the benthic communities in Arctic regions: Alaska Department of Fish & Game Modification of clam density and demography; Physical effects on sediments, with biological consequences Oliver et al. 1983

14 Trophic biology of pinnipeds 13 Walruses: Benthic feeding: Cool underwater videos! Goran Ehlme Reference: Levermann, N., A. Galatius, G. Ehlme, S. Rysgaard, and E.W. Born Feeding behavior of free-ranging walruses with notes on apparent dextrality of flipper use. BMC Ecology 3: 9.

15 Polar bear foraging 1 Primary foraging habitat: Sea ice; Primary prey: Phocid seals on the ice. Key influence on all aspects of the life histories of Arctic pinnipeds; Also prey on walrus and belugas.

16 2 Polar bear foraging When stranded on land as a result of poor ice conditions: Feed on whatever is available and catchable, including vegetation.

17 1 Sirenian foraging Key general patterns: 1. All species herbivorous; 2. All species with dentition resembling terrestrial mammalian herbivores and designed for grinding vegetation; 3. All species with continuously deciduous teeth, erupting in the posterior jaw, moving forward, and shedding from the anterior jaw; 4. All species with primary cellulose digestion in the colon (similar to elephants and hyraxes); 5. All species with relatively low metabolic rates and, with some exceptions, minimal cold tolerance.

18 2 Sirenian foraging Key general patterns: 1. All species herbivorous

19 3 Sirenian foraging Manatee Key general patterns: 2. All species with dentition resembling terrestrial mammalian herbivores and designed for grinding vegetation Manatee Reindeer

20 4 Sirenian foraging West Indian manatee Key general patterns: 3. All species with continuously deciduous teeth, erupting in the posterior jaw, moving forward, and shedding from the anterior jaw Shedding of oldest teeth New eruptions

21 Sirenian foraging 5 Key general patterns: 4. All species with primary cellulose digestion in the colon (similar to elephants and hyraxes)

22 6 Sirenian foraging Key general patterns: 5. All species with relatively low metabolic rates and, with some exceptions, minimal cold tolerance.

23 7 Sirenian foraging Patterns by families: Dugongs (dugongidae): Obligate bottom feeders; Forage primarily on sea grasses; May cause ecologically significant disturbance to sedimentary ecosystems.

24 Sirenian foraging 8 Patterns by families: Sea cows (hydrodamalidae or dugongidae): Obligate surface feeders; Forage primarily on kelps; Probably able to forage in the rocky intertidal zone during winter despite great size and limited mobility.

25 Sirenian foraging 9 Patterns by families: Manatees (trichechidae): Generalized feeders; Consume a wide variety of plant types at surface, midwater, and on the bottom; Amazonian manatee may be able to tolerate obligatory seasonal fasts imposed by seasonal changes in river water levels.