Food Chain


Rescue centers commonly see pinnipeds that have stranded for the following reasons:

  • the very young. They have no clue about survival, cannot find food after weaning, and are found on beaches underweight, dehydrated, and often with secondary injuries. The vast majority of animals in centers are young-of-the-year.
  • the very old. They commonly have kidney failure, chronic infections, severe parasite infestations, or cancers.
  • injured animals. Common injuries involve naturally occurring injuries caused by shark bites or sting ray barbs, by competition and fighting with each other. They have lost eyes or have infections from cuts or scrapes. Other injuries include human-inflicted problems--- such as collision with boats, entanglement in fishing equipment, swallowing of fishing equipment, gunshot wounds, or stabbing or spearing. Some of the human wounds are purposeful. Others are inadvertent, caused by carelessly discarded items in the ocean. Still others are the product of competition between humans and animals for the ever dwindling resources in the sea.
  • ill animals. Animals are often admitted with diseases such as San Miguel Sea Lion Virus or Seal Pox. Pacific coast animals are also now exposed to morbillivirus (canine distemper). Some animals suffer from leptospirosis, lung worm or other parasitic afflictions. They can also have illness similar to those commonly found in humans: viral infections, pneumonia, or bad pregnancies.


    For a more complete discussion of these topics refer to:

    • Marine Mammal Protection Act
    • US Fish and Wildlife Service, Administration of the Marine Mammal Protection Act of 1972, Department of the Interior, 1995.
    • "Easy Target", The Sonoma County Independent, Dec 4-10, 1997
    • Geraci, Joseph and Lounsbury, Valerie, Marine Mammals Ashore, A Field Guide for Strandings, Texas A&M Sea Grant Publication, Galveston, Texas, 1993.


      To test your understanding, complete the following:

      Which of the following are violations of the Marine Mammal Protection Act in regard to wild animals

      a. Feeding a marine mammal

      b. Walking close to an animal, but not disturbing it

      c. Walking close to an animal, causing it to flee back into the ocean

      d. Taking photographs of your children on the back of an elephant seal on the beach

      e. Giving a starving marine mammal milk or food

      f. Buying fish at Fisherman's Wharf and throwing them to the seals below

      g. Chasing mammals away from your fishing net with a loud noise

      h. Snorkeling with dolphins in the ocean that approach you of their own will

      i. Dragging a seal back in the ocean from the beach

      j. Letting your dog chase a seal on the beach, scaring the seal

      m. Touching a dolphin that swims by you while you are snorkeling in the ocean

      Activities for students

      • Write to the congressional representatives to support renewal of the MMPA or other environmental legislation.
      • Participate in beach clean-ups, storm drain labeling campaigns,or other watershed projects
      • Visit a rehabilitation center for some kind of animal. Find out what kind of work is done there. Can you provide a service project that will benefit them?
      • Support establishment of national seashores, wetlands, and nature preserves to provide habitat for wild animals.
      • Each one, teach one. Pass on what you learn to others.