Feeding Behavior in Animals

All animals require energy from food to move, grow, and repair. The act of taking in food is called feeding, while the way an animal finds, captures, handles, and consumes that food is called its feeding behavior. This is different from diet, which describes what an animal eats, as well as from foraging, which refers to how an animal searches for food and chooses what to eat.^[1]

Food is not equally easy to find, catch, or reach. Some prey, such as fish or insects, move quickly, while others, like worms, may stay hidden in the soil. Similarly, some foods, such as nectar, are held deep inside flowers, while plankton simply drifts through water. Because of these differences, animals use different feeding behaviors, often shaped by the body structures they have. For example, flamingos have specialized bills that help them filter food particles from water, while seahorses possess narrow snouts to suck in small prey.^[2]

Types

To understand variation in animal feeding behavior, two main factors are considered: the mode of ingestion (how food enters the body) and the food type (what is consumed).

1. By Mode of Ingestion

These types describe how food enters the mouth or body.

• Bulk feeding — takes in large food pieces
• Fluid feeding — draws in liquid food
• Filter feeding — strains food from water
• Ram feeding — moves into food
• Suction feeding — pulls food inward

2. By Food Type

These types describe the main kinds of food an animal depends on.

• Living or Fresh Biological Matter

  • Animal-Based Feeders

    • Carnivores — animals or animal-derived food

      • Insectivores — insects
      • Piscivores — fish
      • Molluscivores — mollusks
      • Invertivores — invertebrates
      • Myrmecophages — ants or termites
      • Araneophages — spiders
      • Avivores — birds
      • Vermivores — worms
      • Corallivores — coral polyps
      • Spongivores — sponges
      • Ovivores (Egg Predators) — eggs
      • Haematophages (Sanguivores) — blood
      • Durophages — hard-shelled prey
      • Mucophages — mucus
      • Keratophages (Ceratophages) — keratin material

  • Plant-Based Feeders

    • Herbivores — plants or plant material

      • Feeding Style

        • Grazers — low vegetation, like grass
        • Browsers — high-vegetation, like leaves, shoots, twigs

      • Plant Specialization

        • Folivores — leaves
        • Graminivores — grasses
        • Frugivores — fruit
        • Granivores — seeds
        • Nectarivores — nectar
        • Palynivores — pollen
        • Florivores — flowers
        • Xylophages — wood
        • Exudativores — plant fluids

  • Algae, Fungi, and Microbe Feeders

    • Algivores — algae
    • Fungivores — fungi
    • Bacterivores — bacteria

  • Mixed or Flexible Feeders

    • Omnivores — plant and animal matter

• Dead, Decaying, Waste, or Mineral Material

  • Scavengers — dead animals or carrion
  • Detritivores — dead or decaying organic matter
  • Coprophages — feces

Some feeding behaviors may overlap across the above groups. For example, a cow is a grazer by feeding style, but a graminivore by diet because it feeds mainly on grasses. Similarly, a baleen whale is a filter feeder by mode of ingestion, but a carnivore by diet, as it consumes small animals such as krill.^[3]

Apart from these broad categories, several unusual feeding behaviors have also evolved in the animal kingdom. These include feeding on members of the same species, stealing food from another animal, or even feeding on matter that is not a typical source of food.

• Cannibalism – eating the same species
• Kleptoparasitism – stealing another’s food
• Trophallaxis – sharing regurgitated food
• Pica – eating non-food matter
• Placentophagy – eating the placenta
• Lignophagia – eating woody matter
• Paedophagy – eating young individuals
• Kleptopharmacophagy – stealing chemical substances

After ingestion, food is broken down in the animal’s body in the following ways:

• Extracellular digestion — food is broken down outside cells
• Intracellular digestion — food is broken down inside cells
• Phagocytosis — a cell engulfs the food particles
• Myzocytosis — cell contents are sucked out

Feeding and Ecosystems

How an animal feeds affects more than its own survival. It can also shape other animals, plants, and habitats connected to it. For example, carnivores can influence the populations and behavior of the animals they feed on, especially when they act as predators.^[4] Grazers and browsers can directly affect plant growth in a habitat. Similarly, scavengers and detritivores help break down dead organic matter, returning nutrients to the soil where they can support new growth.