Marine Mammal Predator–Prey Essentials

Taxonomy Essentials

  • Order Carnivora ➔ Families: Ursidae (polar bear), Mustelidae (otters).
  • Sub-order Pinnipedia ➔ Families:
    • Phocidae (true/earless seals): Phoca vitulina (harbor), Halichoerus grypus (gray), Pagophilus groenlandicus (harp).
    • Otariidae (sea lions/eared seals).
    • Odobenidae (walrus).

Predation Fundamentals

  • Predation = consumption of another organism; drives behavior, demography, community structure & evolution.
  • Virtually all marine mammals face predation at some life stage.

Predators by Prey Group

Sirenians

  • Main threats: killer whales, large sharks, crocodiles.
  • Manatees ⇒ low risk; Dugongs ⇒ risk location-dependent.

Pinnipeds

  • High risk terrestrially & aquatically.
  • Land predators: polar bear, arctic fox, humans; pups also taken by jackals, wolves, eagles, etc.
  • Aquatic predators:
    • Polar bear (wait/stalk at breathing holes; targets ringed seals).
    • Pinnipeds on pinnipeds: leopard seal, walrus; male sea lions cause up to 43\% pup mortality.
    • Sharks: >15 pinniped spp. recorded in stomach contents.
    • Killer whales: harbor seals compose >60\% of diet in BC/WA.

Cetaceans

  • Sharks: greatest danger to small, offshore, warm-water species (white, bull, tiger sharks).
  • Polar bear: occasional beluga & narwhal kills in shallow/ice areas.
  • Killer whale: apex threat—targets all cetaceans (incl. blue, sperm); prefers blubber, hunts cooperatively.

Key Shark Predators

  • White shark: shifts to marine mammals with size; harbor porpoise & pinnipeds common.
  • Bull shark: warm coast/river; dolphin specialist.
  • Tiger shark: designed for large prey; dolphin predation observed globally.

Anti-Predator Tactics

Reduce Encounter

  • Hide: seal birth lairs ≈1.5 m deep; multiple lairs per female.
  • Grouping: large or mixed-species odontocete schools dilute risk.
  • Activity shift: alter foraging/rest (e.g., daytime rest by Hawaiian spinner dolphins; haul-out timing in seals).

Respond to Predator

  • Flight/escape.
  • Mobbing & inspection.
  • Active defense: line formations, calf encirclement.