Feeding Ecology - MARI 3090 - Dalhousie University Fall 2023 PDF

MARI 3090 –Marine Mammalogy, Dalhousie University Dr. Amanda Babin, Fall 2023 Christian Khan NOAA Feeding Ecology • Optimal foraging theory • Air-breathing diving animals should minimize costs (travel time without oxygen input) and maximize benefits (energy gain from foraging) • ex. Blue whales...

MARI 3090 –Marine Mammalogy, Dalhousie University Dr. Amanda Babin, Fall 2023 Christian Khan NOAA Feeding Ecology • Optimal foraging theory • Air-breathing diving animals should minimize costs (travel time without oxygen input) and maximize benefits (energy gain from foraging) • ex. Blue whales forage more at night because prey vertically migrate closer to the surface healthhamster.com What determines how and what you feed on? • • • • Body size Prey distribution (migrations) Environmental conditions Individual preference flickr • Need to maximize fitness • Depends on: Physiological Requirements • Basal metabolism • Growth • Energy for extended dives • Excess energy to allow for fasting • Energy for migration • Energy for lactation • Depends on foraging success Stellwagen Bank National Marine Sanctuary Life History Strategies • • • • Store up ‘capital’ Typically larger animals Excess energy for fasting Tend to migrate from colder feeding grounds to warmer breeding grounds Skyler Ewing • Capital Breeder/Feeder • • • • Live ‘paycheck-to-paycheck’ Typically smaller animals Nearly constantly feeding Tend to have shorter migrations based on movement of prey Nick Hawkins • Income Breeder/Feeder Capital Breeder • Large baleen whales (blue, humpback, right, bowhead) • Breed and give birth in warmer waters because young do not yet have a thick blubber layer, and because there are fewer predators • Ex. North Atlantic Right Whale (NARW) migrate from Gulf of St. Lawrence/Bay of Fundy to feed in spring-summer to Georgia/Florida to breed in fall-winter popsci.com • Larger species of phocid seals (elephant, grey) • Adult male otariids (Steller sea lion) Income Breeder • Ex. harbour porpoise moves around the continental shelf and coastal areas, following prey and avoiding ice • Smaller phocids (harbour seal, ringed seal) • Adult female otariids aquablog.ca • Sea otter (local migrations) • Most odontocetes Feeding Techniques of Mysticetes • Skimmers • Gulpers • Grubber • Feed on zooplankton and small fish (lower trophic level) • Elastic symphysis (flexible joint in chin to allow mouth to expand) Skimmers (aka ram feeding) • Feed on copepods where concentrated, long baleen • Right whale • Bowhead whale (migrate based on ice and prey) aHeather Koopman SMM2017 todayifoundout.com • Bay of Fundy copepod abundance down by half, quality down 23%a • Two-year lag between high prey abundance and calving in Right whales Gulper • Rorqual whales – 70-80 pleats/ventral grooves • Ex. Blue whale, in our area migrates from Greenland to subtropics • Lunge feeding (10 km/h) • Feed on krill, capelin, and other schooling fish • Shorter, fewer, and more coarse baleen socialphy.com • Oral plug Rorqual specialists – Humpback whales • Rolling on bottom for sandlance • Touch noses • Risk of entanglement ngsspheomena.com • Can be cooperative • Bubble-net feeding fisherycrisis.com Grubber – Gray whale • Feed on amphipods and crustaceans in the bottom sediment • Wears down short baleen (fewer, coarser) • Longest migration, 15-20,000 km odu.edu Nancy Culp Zaretzke • Generally fish and squid eaters, sometimes other marine mammals (higher trophic level) • Symphyseal mandible (joint fused for biting) Odontocetes • Bioaccumulation Mysticetes beamreach.org Feeding Techniques of Odontocetes Feeding Techniques of Odontocetes • Can coral fish into a bait ball • Population- or family-specific techniques • Bottlenose dolphins • Beaching • Lobtail feeding • Beluga, beaked whales • Suction feeding • Sperm whale • Ambergis inhabitingtheanthropocene.com ngm.nationalgeographic • Primarily opportunistic feeders • Feed on a large variety of prey such as fish, cephalopods, invertebrates, and sometimes birds! • Super-specialists cbc.ca Feeding Techniques of Pinnipeds Feeding Techniques of Sirenians • Graze seagrass and other vegetation with strong, prehensile lips iowalum.com savethemanatee.org Feeding Techniques of Sea otters and Polar bears • Sea otters use tools to break open shells • Hold rocks in pockets of skin • Favourite rock can be passed down through generations • Polar bears are ambush predators • <2% foraging success • Catch a seal every 4-5 days • Both keystone species • Sea otter → urchin → kelp • Polar bear → seal/whale → birds, foxes, etc. Prey Selection Studies • Methods: • Direct observation (crittercams!) • Collection of indigestible parts (squid beaks, fish scales) from stomach contents and feces • Fatty acid/stable isotope analyses Wimmer and McLean 2021, adapted from Chami et al. 2019 The Whale Pump • Feed at depth, defecate at surface • Whales are farmers (fertilize) • Phytoplankton adds O2 to the atmosphere, removes CO2 then sinks to the seafloor • Mix nutrients in waters at various depths and from temperate to tropical waters • 1 whale>1000 trees worth of C Take Home Messages • Optimal foraging theory • Feeding techniques of mysticetes and odontocetes • Rorquals • Capital vs. income breeder/feeder • Methods of foraging studies • Whale pump and importance of their role in the ecosystem lifewithdogs.tv Thank You!