What is a Primary Consumer in Ecology? Examples in a Food Chain

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What is a primary consumer?

A primary consumer in ecology is an organism that eats plants as food. In an ecosystem where there is a complete food chain, the primary consumer predominantly occupies the second trophic level of the food web or food chain.

Herbivores are the commonest primary consumers and they are also known as heterotrophs because they do not produce their own food. Rather, they are primarily dependent on autotrophs, which are plants that produce food through photosynthesis.

Before a deep dive into what is a primary consumer, a brief summary of what are consumers need to be done.

What are consumers?

Consumers are groups of organisms that cannot produce nor manufacture their own food, but they rely on other organisms for their food. Within the food chain, consumers can be divided into three categories: primary, secondary, and tertiary.

Secondary consumers

Carnivores that eat other animals are the commonest secondary consumers. Omnivores that eat both plants and animals are also considered secondary consumers.

Tertiary consumers

Tertiary consumers, also called predators, are at the top of the food chain and can feed on both secondary and primary consumers. These tertiary consumers could be omnivorous or completely carnivorous. One of the best examples of a tertiary consumer is humans.

Now that a summary of what consumers are, a closer look at what is a primary consumer can now commence.

Definition of Primary Consumers 

A primary consumer can simply be defined as an animal that solely feeds on plants for their survival. In the intake of these plants, there are different types of feeding strategies used by these primary consumers in the food web in order to obtain the desired nutrient for survival and reproduction.

For example, photosynthetic algae are eaten by algivores, whereas plant nectar is sucked by nectavores, while the plant fruiting bodies are devoured by frugivores. In addition, those that feed on grains and seeds are called granivores while folivores eat leafy material and fungivores eat heterotrophic fungi such as mushrooms. All these organisms are sub-classes of herbivores based on the desired parts of plants they eat in order to maximize the effectiveness of foraging behavior.


Primary consumers can be found in all biomes and fill a variety of niches. For instance, in the desert biome, the primary consumer found there are butterflies that feed on cactus plants, while in the ocean biome zooplanktons that feed on phytoplankton are the major primary consumers.

Furthermore, in the pond biome, the insect larvae are present and they feed on algae, whereas in the grassland biome, the primary consumer present is the grasshopper and it feeds on grass.

Some primary consumers have developed physiological adaptations. These enable and assist them to process the carbohydrates produced by photosynthesis from primary producers.

For example, herbivores developed the physiological adaptation of having their teeth in rows characterized by being wide and flat. These characteristics enable them to rasp, grind and tear tough plant materials and woody stems in their search for carbohydrates and the necessary nutrients.

Many primary consumers also have symbiotic relationships with bacteria that live in a particular organ called the cecum that help them with plant digestion.

Examples of primary consumers

  1. Ruminant animals
  2. Birds
  3. zooplankton

The above-listed are the examples of primary consumers and they will be discussed subsequently.

Ruminant animals

Cows, goats, zebras, and giraffes are examples of primary consumers and these herbivores feed on plant material like grass, branches, and roots. The plant cell walls contain cellulose, which is difficult to break. As a result of the cellulose, ruminants have developed an adaptive system that allows them to obtain nutrients through fermentation and digestion.

The procedure is carried out in four specialized chambers of their stomach and it starts when the chewed plant material is directed from a ruminant’s mouth to the first digestive chamber, the rumen, and then the reticulum. The sophistication of the ruminant stomach demonstrates the difficulties that large animals face when obtaining nutrients from plant carbohydrates.


Many birds are examples of primary consumers because they only eat seeds, cherries, and fruits. Birds with plant-based diets typically have morphologically adapted beaks and they can easily exploit their food source with such beaks.

For example, parrots, parakeets, and toucans have exceptionally strong beaks that allow them to easily crack nuts and the beaks also serve as a stabilizing tool for climbing large trees and reaching the fruits at the tree’s highest points. Hummingbirds and other similar species, on the other hand, have very small, elongated, and pointed beaks that can reach nectar deep inside the flowers with such beaks.

Because they primarily feed on grains and seeds, many canaries, finches, and parrots have a short, hard, and pointed beak and with such beaks, they can pick the grains with great precision.


Zooplankton is microscopic organism that lives in the marine ecosystem as aggregates; they are examples of primary consumers in the ocean. Zooplankton consists of protozoa and metazoans (crustaceans and mollusks) in the juvenile stages. It is predominantly heterotrophic and obtains nutrients from the coal produced by photosynthesis.

This process of being heterotrophic is aided by the marine ecosystem’s primary producers, which convert organic coal into usable energy.

Furthermore, zooplankton consumes food via filtration capabilities, for instance, when water passes through specialized filters in this mode of feeding, the phytoplankton present in the water is filtered and digested by the zooplankton.

Primary consumers in the food chain

There are a plethora of other primary consumers on the planet earth and the majority of them are much smaller and have little effect on the ecosystem. Squirrels, mice, and beetles are examples of primary consumers in the food chain that occupies the second trophic level of the food web. It is also important to keep in mind that because their diet varies, some primary consumers may fall into other trophic levels. A bear, for example, qualifies as a primary consumer when it feeds on berries.

List of animals that are primary consumer

  • Cows
  • Shrimps
  • Parrots
  • Parakeets
  • Toucans
  • Finches
  • Canaries
  • Rabbits
  • Zebras
  • Giraffes
  • Goats
  • Sheep
  • Aquatic mites
  • Crustaceans
  • Insect larvae
  • Bettles
  • squirrels
  • Rotifers

The above-listed animals are some of the examples of primary consumers.

Other primary consumers in the ocean

  • Shrimps
  • Aquatic mites
  • Jellyfish
  • Snails
  • Crabs

The above listed are some of the examples of primary consumers in the ocean. In summary, all zooplankton (organisms that feed on phytoplankton) are examples of primary consumers in the ocean.

Functions of Primary Consumers in an Ecosystem

Primary consumers play an important role in ecosystems as they aid in the transfer of energy within the ecosystem, which is necessary to maintain its balance and avoid collapse. But how do they accomplish this?

We know that secondary and tertiary food consumers in the food chain are unable to produce their own food via photosynthesis and they are also unable to consume plants. Thus, they rely on primary consumers to meet their nutrient and energy requirements.

This is how the procedure works: plants, as primary producers, use sunlight to produce their own food via photosynthesis, they are therefore referred to as “autotrophs“. Following that, primary consumers feed on plants and are then eaten for food by secondary and tertiary consumers.

Thereafter, the organisms at the top of the food chain, including humans, eventually die and decomposers, such as bacteria and fungi, eat the remains for nutrients. The chemical elements of those nutrients are then recycled back into the ecosystem by these decomposers.

A classic example of this procedure (transfer of energy in the food web) in the terrestrial ecosystem is seen when a caterpillar being an example of a primary consumer of plants is then eaten by birds and other small animals.

Another example of this same procedure in the marine environment is observed when a shrimp being an example of a primary consumer in the ocean feeds on phytoplankton to gain energy. Afterward, large marine animals, such as whales, consume shrimp as food to obtain energy.

From the two examples of food chains in different ecosystems, it can be seen how energy is transferred across the food web or food chain. This procedure simply stresses the functions of the primary consumer in the food web.

It’s worth noting, that during the energy transfer process, only 10% of energy is normally transferred from one trophic level to the next. This explains why an ecosystem typically has more primary consumers and fewer top-level predators and this phenomenon gives the ecosystem energy transfer diagram its distinctive pyramid shape.

Importance of a primary consumer in the ecosystem

  • They aid in the ecological welfare of the food chain, and the perfect balance between them, which prevent animal overpopulation, pest extinction, and allow the ultimate goal of feeding humans.
  • Without a proper balance between the primary consumers and other consumers, the ecosystem may collapse, resulting in the extinction of all affected species. This would almost certainly result in a tainted and inefficient food supply chain.


Is a rabbit a primary consumer?

Yes, rabbits are primary consumers because they feed on plant-based products to gain the necessary nutritional requirements needed for their growth and development.